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Top 7 Full-Spectrum CBD Oil Brands

We were strategic with our search and identified four main factors to consider before putting this list of best full-spectrum CBD oil products together. Below is what we measured each brand and product up against:

  • Reputation

Reputation says a lot. Reputable companies have won awards, are supported by a vast consumer base, and stand the test of industry expert reviews.

  • Ingredients

You should never consume a CBD oil product without knowing what’s in it. We only recommend companies that use the finest, natural ingredients.

  • Independent Testing

A crucial step to verify the potency and purity of CBD products, we made sure every brand we share below tests all their products.

  • Extraction Processes

Companies should be transparent about their processes; whether the hemp plant variety of the cannabis plant family they use in their products is organic, what type of method they use to extract the CBD from the plants, and more. This list contains companies that are proud to share their high standards and processes with their customers.

Top Full-Spectrum CBD Oils – Reviews

1. CBDfx – Editor’s Choice in Best Full-Spectrum CBD Oil


  • 60-day customer satisfaction guarantee
  • Multiple concentration options
  • Vegan and gluten-free CBD oil
  • CBD plus CBD formula


  • None

Product Highlights
On the CBDfx website, you’ll find that they have quite a selection of CBD products. A couple of their products are new and are labeled as such. They could be worth exploring if you’ve tried other products from this brand. Their classic full-spectrum CBD oil contains CBN for the ultimate calming tincture that helps you relax. It’s designed specifically to calm you down. This full-spectrum CBD oil is available in five different concentrations up to 6000 mg of CBD.

One of their newer products is their CBD plus delta-9 THC drops. This is an ultimate chill blend that contains full-spectrum CBD along with 2.25 mg of THC per serving. It has a natural blueberry flavor and allows you to dial back your stress and relax. You’ll feel a deep sense of peace when you try this product, but be warned because it may cause a psychotropic effect. This one is available in three concentrations up to 6000 mg.

The final full-spectrum CBD oil product that CBDfx offers is their delta-9 THC drops plus CBN. Not only does this one come with a warning because it could have some psychotropic effects, but it is packed with CBN to really help you relax into sweet dreams. No matter the reason you’re having trouble sleeping, this CBD oil will take care of it. You’ll wake relaxed and rejuvenated. It’s perfect because it only contains the maximum legal amount of delta-9 THC!

About the Company
CBDfx keeps innovating their products because they’re committed to providing you with little drops of wellness with each CBD oil they offer. As they keep expanding their product list, you can tell that they’re really listening to their consumer base and offering a variety of different products to ensure all customers are happy with what they receive. Their formulas are completely vegan, using CO2 extracted CBD oil. You’ll find that they have a wide variety of other products that you can check out once you’re on their website. You might be looking for top quality full-spectrum CBD oil products, but you may also find that there is a broad-spectrum CBD oil or CBD isolate that you’re interested in trying. You won’t know unless you do, so we encourage you to check out their other offerings as well.

2. CBD American Shaman – Close Second


  • High bioavailability
  • Water-soluble CBD oil
  • Delicious, mouth-watering flavors
  • Fast-acting formulas


  • CBD products have limited strength options

Product Highlights
CBD American Shaman has taken a different approach to its full-spectrum CBD oils. Instead of following the lead of other CBD companies, they developed proprietary nanotechnology that makes their water-soluble formula up to 10 times more bioavailable than other full-spectrum CBD oil products you’ll find on the market. Each CBD oil contains 300 mg of hemp oil extract per bottle. Even though their proprietary nanotechnology is their highest selling point, they’ve also developed flavorful options for customers who prefer something different. Try their grape, piña colada, cherry limeade, or go for the natural hemp flavored bottle. Hundreds of customers purchase from CBD American Shaman on a weekly basis and for good reason.

About the Company
Typically, when you shop for CBD oil online, you’re purchasing fat-soluble products. We had to highlight CBD American Shaman in this list because of their initiative and their ingenuity—they stepped outside the norm to try something different. Each one of their full-spectrum CBD oil products is water-soluble, meaning you can pour it into your favorite drink and be on your way. They break down their CBD oil using that unique, patented nanotechnology, which means that you get to harness the therapeutic benefits of CBD more quickly than if you were to try a fat-soluble CBD oil. Plus, their scientific innovation makes it so that each time you dose with their full-spectrum CBD oils, you’re getting 10 times more healing properties of CBD.

3. Green Roads – Runner Up


  • Products formulated by pharmacists
  • No artificial ingredients
  • Vegan and gluten-free
  • Tested by independent labs


  • No fruity or minty flavor options, but with this formula, you won’t miss any flavoring

Product Highlights
Green Roads offers a full-spectrum line of CBD products with a range of concentrations. If all you need is a little bit to get you going through the day, you can buy their full-spectrum CBD oil that contains 10 mg/mL. For a more moderate dose, you can select their 25 mg/mL option or if you’re looking for an extra-strength product, you’ll love that they’ve created a 50 mg/mL option. This formula, no matter which strength option you select, is pharmacist formulated without any artificial colors or flavors and is also certified vegan and gluten-free. Green Roads combines at least six ingredients to make their formula so that you can have a better absorption experience. Although the CBD oil is not flavored, you’ll find that it has a naturally sweet taste that might remind you of caramel candy.

About the Company
We included Green Roads in this list producers because they make sure that with their ingredients, they’re maximizing absorption rates for their customers. Their in-house pharmacists are always working hard to innovate their full-spectrum CBD oil options with a distinctive, sweet, natural flavor, unlike other CBD oils. As soon as you visit their website, you have the option to filter the products toward the top of the screen. Simply select the full-spectrum option and it’ll only show you their full-spectrum CBD oil products. Select whether you want the mild, moderate, or mighty dose and be well on your way to check out. You’ll also find that they have received several awards for their products and that they have tens of thousands of five-star reviews from very happy customers. They’re proud to farm their hemp in America and also keep all their products cruelty-free.

4. CBDistillery – Honorable Mention


  • Subscribe and get 20% off
  • 60-day customer satisfaction guarantee
  • Natural farming practices
  • Multiple formulas are available


  • You have to pay for shipping unless you have at least $75 worth of products in your shopping cart

Product Highlights
CBDistillery is a fun shopping website. Over on the left-hand side, you can see all their CBD products and CBD oils categorized. Just select the top option for full-spectrum CBD products and you’ll immediately be provided with the products that match your selection.

They have several options, including their primary full-spectrum CBD oil option, which is a 1000 mg tincture in a 30 mL bottle. This is a great go-to if you’re not sure what to select. If you want to go a little bit lower on the dose or a little bit higher, they also offer a 500 mg and 2500 mg full-spectrum CBD oil. If you’re getting adventurous with your CBD oil, check out their mango-flavored tincture. The taste is juicy and sweet but not overpoweringly so. They also have a limited edition oil that’s still available at 1000 mg with a peppermint flavor.

For sleep, they offer a sleep synergy CBN plus CBD extra strength CBD oil tincture. This one should only be used at night time when you’re about to hop into bed. With the use of CBN combined in this extra-strength formula, you’ll find that you are drifting off with deep belly breaths into happy dreams faster than you could count sheep. You can save if you bundle some of their hemp-derived CBD products so look out for sales as well.

About the Company
CBDistillery offers a diverse range of products. Their customers love having a great CBD oil to count on, whether it’s in the morning to help them deal with aches and pains or in the evenings when they’re ready to settle down and relax. Imagine feeling relief from discomfort while getting a mood boost! That’ll change how you interact with others both at home and at work. Plus, when you’re getting the true, deep rest your body needs every evening, you begin to emanate a different type of energy and the people around you are sure to notice. Don’t be stingy when they ask, tell them your full-spectrum CBD oil secret!

5. Absolute Nature CBD – Growing Reputation


  • 100% natural ingredients
  • Certified and USDA organic
  • Sign up for exclusive offers
  • Lab-tested and eco-friendly


  • The wealth of information on the website is a little crowded (scroll down to add CBD products to your shopping cart)

Product Highlights
Absolute Nature CBD has a line of full-spectrum CBD products, including hemp oil drops and soft gels. At first glance, it might be difficult to differentiate between their products. But that’s what we’re here for! Their first full-spectrum offering is a tincture that contains 500 mg of full-spectrum CBD. This formula contains nothing except a whole plant full-spectrum oil and MCT oil to increase absorption. This is considered a milder serving of CBD and is perfect for people who would prefer not to venture too far into the heavier doses. If 500 mg of CBD doesn’t cut it for you, they’ve also perfected a 1000 mg CBD oil tincture. This one delivers 33 mg of CBD plus 5 to 10 mg of additional beneficial cannabinoids per mL serving.

Especially in higher doses, CBD can work as a mild sedative. If you’re looking for some relaxation and clarity but don’t want to have any kind of drowsiness, even for a moment, you should choose their CBG plus CBD oil drops at 500 mg of CBG and 500 mg of CBD. CBG is fantastic for using during the day and can help to elevate your CBD oil, keeping you energized and alert to tackle whatever is ahead of you. These premium quality CBD oils are made with organically grown, select non-GMO hemp cannabis plant varieties that are well-cared for by Colorado farmers.

About the Company
Absolute Nature CBD made this list of best full-spectrum CBD oils at number five because its formulas are award-winning, eco-friendly, and organically grown. They only use 100% natural ingredients and make sure that every single batch of their full-spectrum CBD is pesticide-free. To confirm that each of their products is safe and potent, they lab test every batch. You can easily find the lab results as part of the product description. Just look over at the images. They also offer tons of information on CBD on their website, helping you understand the difference between full-spectrum, broad-spectrum CBD, and CBD isolate. They’re certified USDA organic, which is a certification of which not everyone can boast. They also produce all their CBD products using clean, safe, solvent-free CO2 extraction to preserve the plant’s natural beneficial compounds.

6. Joy Organics – Organic Focused


  • THC included for the most therapeutic benefits
  • USDA organic formula
  • 90-day customer satisfaction guarantee
  • Subscribe to get 20% off


  • There’s only one flavor option available for this CBD oil tincture

Product Highlights
Joy Organics, in keeping with their quest toward innovation, has meticulously designed their first full-spectrum CBD formula. This tincture is flavored with fresh lime for a zesty way to obtain flavonoids, terpenes, and minor cannabinoids, as well as CBD to calm your mind and relieve muscle tension throughout your body. Each one-ounce bottle has 30 servings; the strength you select is up to you. You can choose between 350 mg, 900 mg, 1350 mg, or 2250 mg of CBD per bottle.

About the Company
Joy Organics masterfully mixes compassion, honesty, and quality. Customers enjoy their premium products, and they provide service that matches their high standards of quality. Joy, the company’s founder, needed an organic product to lean on because she was having trouble sleeping. Joy Organics has quickly established itself as a pioneer in the CBD sector, setting new standards for testing and quality. They’re one of the first large CBD firms to offer organic CBD oils that have been certified by the USDA.

7. Raw Botanics – Great Service


  • Energizing formula
  • All-natural citrus flavor
  • Made from organically grown hemp cannabis plant varieties
  • Ethically sourced and cruelty-free


  • This formula is best for daytime use; for a sleep or nighttime formula, you should consider a different CBD oil

Product Highlights
The Raw Botanics Co. is making a name for itself in the CBD industry with its new 500 mg CBD hemp extract that they call Rise. This full-spectrum CBD oil formula was developed to help you get your day started on a good note without having to rely on caffeine to give you an energy boost. It’s a morning ritual you can use any time of the day. Instead of that 2 o’clock feeling when you start to feel sluggish and you want to reach for the coffee, you can just reach for Rise instead. This formula has an all-natural citrus flavor and adaptogens that help you tackle the day, no matter how tough it gets. You’ll find that it increases your focus while improving your energy and making you even more resilient when it comes to handling the stressors in your life. Aside from making you a better functioning human, it also works within your body as an anti-inflammatory and to support your immunity. With all these health benefits, it’s hard to look past it.

About the Company
The Raw Botanics Co. wants you to relax, recover, and re-balance with their products. Combining exotic hemp-derived cannabinoids, custom terpenes, and botanical adaptogens, they developed formulas to help you both feel and perform at your best. Reach out to their customer service team for honest guidance if you’re not sure which type of product you prefer. However, their CBD oil tinctures are well-loved by many customers who have tried it and felt the difference. One verified reviewer calls it “a great substitute for that afternoon cup of Joe” while others love that this formula is keto-friendly. The energy boost is subtle, and the flavor is described as having notes of orange, tangerine, and lemon.

CBD Types: Isolates, Full-Spectrum & Broad-Spectrum CBD Oil

If you think of the types of CBD in terms of a hierarchy, CBD isolate can be found at the bottom. It’s not to say that the best CBD isolate isn’t as reliable of a product as the best full-spectrum CBD oil, however, it is missing several of the beneficial compounds that are included in full-spectrum and broad-spectrum CBD products. Below, we break down the difference.

Full-spectrum CBD contains all cannabinoids and terpenes while broad-spectrum contains some cannabinoids and terpenes. CBD isolate product only contains CBD, leaving out all cannabinoids and terpenes. When you purchase a full-spectrum CBD product, what you get is the maximum amount of phytochemicals in the CBD oil, including some traces of THC. A good full-spectrum extract is quite rare actually! Many of the extraction procedures followed by subpar CBD companies cause a significant loss of both terpenes and flavonoids.

You’ll find that the best full-spectrum CBD oil products tend to have a darker color than if you compared it to a CBD isolate product. You’ll also notice that full-spectrum CBD has a much earthier and natural flavor than other broad-spectrum CBD or CBD isolates. The broad-spectrum is a little bit different because it does typically retain a good amount of phytochemicals (except without THC). So, while you’re getting the full “entourage effect” when you use full-spectrum CBD oils, when you try broad-spectrum CBD, you are getting only some of the benefits of all those compounds that work together.

Broad-spectrum CBD is created in a variety of ways, either by extracting a certain amount of chemical compounds, including extraction of THC, or by simply adding terpenes, flavonoids, and other minor cannabinoids to a CBD isolate. Although you still get that natural, earthy flavor with a broad-spectrum CBD, when you compare between a full-spectrum product and a best broad-spectrum CBD product, you’ll find that the broad-spectrum CBD has a much milder taste.

A CBD isolate is the purest form of CBD that you can purchase. It typically has a 99.9% purity and leaves out all the terpenes, flavonoids, and especially THC from the final product. Processing for these types of products can get pretty expensive, which is why you may notice a price difference between full-spectrum CBD and CBD isolate products.

Benefits of Full-Spectrum CBD

To offer a quick summary of full-spectrum CBD oil, you should understand that phytocannabinoids, or hemp-derived cannabinoids, interact with your body’s receptors to generate a wide range of euphoric and therapeutic effects. Terpenes are the compounds that give cannabis (hemp is part of the cannabis plant family) its aroma and herbaceous flavor, and they help cannabinoids generate several different effects like pain relief, anxiety relief, and sleep support. These terpenes lay the groundwork so that cannabinoids can get busy supporting your whole body health. Flavonoids are an additional set of compounds that are similar to terpenes but that operate in their own way to deliver diverse medicinal benefits. It’s all these interactions that make full-spectrum CBD the most sought-after CBD type. And it lives up to the hype!

Some of the benefits you can expect when you start taking full-spectrum CBD oil include:

Analgesic Effects
CBD oil has become quite popular due to its ability to naturally treat pain. When you take it, it acts as an anti-inflammatory and helps to relieve stress all over your body. When it comes to pain management, the cannabinoids included in full-spectrum CBD oil are particularly effective. CBD can help you enhance your overall quality of life, whether you’re healing from an injury or suffering from chronic pain.

Improved Skin Health
CBD oil is also proven to help you create and sustain healthy skin if you have persistent skin disorders like eczema or dermatitis. CBD oil is high in vitamins and fatty acids, which strengthen and protect your skin from bacterial and fungal problems. Hemp oil’s fatty acids are also believed to restore your skin and prevent it from oxidizing, allowing you to have a more beautiful glow.

Stress and Anxiety Relief
Anxiety is an unpleasant sensation on its own, but if you have chronic anxiety, you are certainly aware that it affects other elements of your life. CBD has been demonstrated to help ease all the symptoms associated with daily stressors, as well as to strengthen the immune system and keep you robust and healthy. CBD can help by providing cognitive support. People who use CBD regularly experience substantially less worry and discomfort.

How to Use CBD Oil

CBD oils should be ingested by placing the oil underneath your tongue. This produces the best results. Before using the dropper to extract your dose from the CBD oil bottle, give it a good shake. Once you’ve got the dropper, drip the CBD oil beneath your tongue and hold it there for at least 30 seconds (longer if you can) to allow it to absorb. After thirty seconds or more have elapsed, you can swallow the CBD oil. When you consume it this way, effects can take as little as fifteen minutes to become noticeable.

Some CBD oils can be blended with food or drinks to make them more palatable, but because the CBD oil must go through your digestive system, expect the benefits to take longer. Remember the water-soluble variety from CBD American Shaman? Those are perfect for dropping into your morning orange juice or tea! This could be a welcome aspect of your morning ritual but if you’re more concerned about experiencing the therapeutic effects more quickly, ingesting the CBD oil sublingually is best.

CBD Oil Dosage

The amount of CBD oil you take is determined by your body mass index, the rate of your metabolism, and the overall chemistry of your body. It also depends on the amount of CBD in the full-spectrum CBD oil you choose. An extra-strength product may only require half a dropper full while a lower dose of CBD oil may require a full dropper full. To begin, follow the product’s instructions and give yourself some quiet time to monitor your body’s reaction. Once you’ve figured out how CBD oil affects you, you can change the dosage to suit your needs.

For some people, the effects of CBD are felt right away. This is primarily due to the way their body processes CBD, but it may not be the case for you. Some customers, in the reviews section of CBD products, note that it took them a couple of days to really start to notice the difference the CBD was making in their lives. The best advice we can give you is to be patient whenever you’re trying out a new CBD product. Full-spectrum CBD oil tends to work better for many CBD users, and it just might take a little trial and error before you find the right dose for your unique body.

Safety and Side Effects

CBD is widely recognized as a safe medicinal supplement that can be used by healthy adults. If you’re taking any medication, you should know that CBD does interact with certain medicines. Talk to your doctor to make sure that incorporating CBD into your health regimen is a safe practice. There are some minor side effects you might experience if you take CBD on an empty stomach or if you take a dose that’s a little bit too high for your body. Some of those may include:

Lethargy or drowsiness
Top quality full-spectrum CBD oil products tend to be more potent, so keep that in mind when dosing for the first time. If you’re selecting a product meant for sleep support, then you can expect some level of drowsiness to occur. However, if you’re looking to incorporate full-spectrum CBD into your daytime routine, make sure that you’re choosing an energizing option that keeps you alert throughout the day.

Stomach discomfort or diarrhea
This usually happens because of the carrier oil used in hemp-derived CBD products. That’s usually hemp seed oil, MCT oil or coconut oil and some people are just more sensitive to these oils in their stomachs than others. If you happen to experience this side effect, try taking your CBD oil with food.


Full-spectrum CBD products are being welcomed into homes throughout the world. The best full-spectrum CBD oil product is the one that works best for your body’s unique chemistry. You have plenty of awesome options to pick from in the list above. Which one of all these products called out to you?

Effects of cannabidiol on brain excitation and inhibition systems; a randomised placebo-controlled single dose trial during magnetic resonance spectroscopy in adults with and without autism spectrum disorder

There is increasing interest in the use of cannabis and its major non-intoxicating component cannabidiol (CBD) as a treatment for mental health and neurodevelopmental disorders, such as autism spectrum disorder (ASD). However, before launching large-scale clinical trials, a better understanding of the effects of CBD on brain would be desirable. Preclinical evidence suggests that one aspect of the polypharmacy of CBD is that it modulates brain excitatory glutamate and inhibitory γ-aminobutyric acid (GABA) levels, including in brain regions linked to ASD, such as the basal ganglia (BG) and the dorsomedial prefrontal cortex (DMPFC). However, differences in glutamate and GABA pathways in ASD mean that the response to CBD in people with and without ASD may be not be the same. To test whether CBD ‘shifts’ glutamate and GABA levels; and to examine potential differences in this response in ASD, we used magnetic resonance spectroscopy (MRS) to measure glutamate (Glx = glutamate + glutamine) and GABA+ (GABA + macromolecules) levels in 34 healthy men (17 neurotypicals, 17 ASD). Data acquisition commenced 2 h (peak plasma levels) after a single oral dose of 600 mg CBD or placebo. Test sessions were at least 13 days apart. Across groups, CBD increased subcortical, but decreased cortical, Glx. Across regions, CBD increased GABA+ in controls, but decreased GABA+ in ASD; the group difference in change in GABA + in the DMPFC was significant. Thus, CBD modulates glutamate-GABA systems, but prefrontal-GABA systems respond differently in ASD. Our results do not speak to the efficacy of CBD. Future studies should examine the effects of chronic administration on brain and behaviour, and whether acute brain changes predict longer-term response.


Autism spectrum disorder (ASD) affects up to 1 in 59 individuals [1]. Of those affected, 70% also have co-occurring conditions such as epilepsy [2], and mood and anxiety disorders [3]. This incurs a high cost to the individual and society: on average the lifespan of individuals with ASD is reduced by 20 years [4]. Given the lack of effective pharmacological treatments, researchers have therefore begun to explore alternative options. These include cannabis and its major non-intoxicating component cannabidiol (CBD), which is derived from the cannabis sativa plant [5].

CBD has already been trialled in several disorders. For instance, preliminary evidence suggests that CBD may improve spasticity [6], pain, sleep disturbances [7], and mobility [8] in multiple sclerosis (MS); and alleviate anxiety symptoms in social phobia [9]. Moreover, alongside anecdotal accounts and case series reports of benefits from medical marijuana in ASD [10], there is evidence that CBD: (i) reduces seizure frequency in two epilepsy syndromes associated with autistic symptoms: Dravet Syndrome and Lennox–Gastaut syndrome [11,12,13]; and (ii) improves ASD-like social deficits in a mouse model of Dravet Syndrome [14]. This suggests that CBD may be worth further investigation in idiopathic ASD. However, before embarking on large-scale clinical trials, a better understanding of how CBD acts on the human brain, and especially in ASD, would be desirable.

CBD has multiple targets, but one aspect of its polypharmacy may be to help regulate excitatory glutamate (E) and inhibitory γ-aminobutyric acid (GABA) (I) transmission, which may influence the activity of excitatory and inhibitory signalling pathways: For example, CBD facilitates glutamate and GABA neurotransmission across the brain through agonism at the transient receptor potential vanilloid type 1 (TRPV1) receptor [15, 16]. Moreover, CBD may increase GABAergic transmission by antagonism at the G protein-coupled receptor 55 (GPR55), and especially in the basal ganglia [14] (BG). In contrast, CBD is thought to be an agonist at prefrontal 5-HT1A receptors, where it suppresses glutamate and GABA transmission [17, 18]. In sum, CBD may act on targets throughout the brain, but especially in the BG and the prefrontal cortex. These actions of CBD upon glutamate-GABA pathways may be especially important in ASD, where post mortem, genetic, and in vivo proton magnetic resonance spectroscopy (MRS) studies have shown abnormalities in both prefrontal and BG glutamate and GABA pathways [19,20,21]; both regions have also been repeatedly linked to ASD core symptoms [21, 22]. Thus, CBD could well impact on prefrontal and BG Glx and GABA levels in ASD, but not necessarily in the same manner as in unaffected individuals (with intact glutamate-GABA systems). However, no-one has investigated this directly.

Therefore, in this study, we tested the hypotheses that CBD impacts on human in vivo glutamate and GABA levels in the BG and dorsomedial prefrontal cortex (DMPFC); but that the response is atypical in ASD. To achieve this, we compared MRS measures of glutamate and GABA in men with and without ASD following a single oral dose of 600 mg CBD or a matched placebo (at least 2 weeks apart) in a randomised double-blind, cross-over design.

Materials and methods


This research was conducted in accordance with the Declaration of Helsinki, at the Institute of Psychiatry, Psychology, and Neuroscience (IoPPN) at De Crespigny Park, SE5 8AF, London, UK (August 2016 to August 2018). The Medicines and Health Research Authority (MHRA) in the UK confirmed the study design was not a Clinical Trial and ethical approval for this study was provided by the King’s College London Research Ethics Committee, study reference HR15/162744. All participants provided written informed consent. Every participant took part in all aspects of this case-control study.

This placebo-controlled, randomised, double-blind, repeated-measures, cross-over case-control study was conducted as part of a larger investigation into the role of phytocannabinoids in ASD; clinicaltrials.gov (identifier: NCT03537950, entry name: HR15-162744). Placebo (PLC) or CBD was allocated in a pseudo-randomised order, so that approximately half in each group attended a placebo visit before CBD; and half attended a CBD visit before placebo. The randomisation was implemented by Prof McAlonan using https://www.random.org/. Participants and researchers directing the study were blind to the assignment. Participants attended for two visits. To allow for drug wash-out, visits were separated each by a minimum of 13 days, with all attempts made to keep between-visit time consistent across all visits and participants. Moreover, the acquisition of data from both groups was mostly overlapping during the same period. On each visit, urine samples were taken to screen for illicit substances (a full list is included below). Subsequently, participants underwent a brief health check, received a liquid oral dose of the pharmacological probe (600 mg of CBD; in line with previous single dose studies of CBD adults (e.g. [23]) or a matched placebo, both provided by GW Research Ltd, Cambridge, UK), and a second brief health check to test for potential acute adverse reactions/side effects. Participants underwent scanning timed to coincide with peak plasma (2 h) concentration. After the scan, participants received a third health check to ensure they had experienced no ill-effects and were fit to leave the department.


Potential participants were excluded if they had a comorbid major psychiatric or medical disorder affecting brain development (e.g. schizophrenia or epilepsy), a history of head/brain injury, a genetic disorder associated with ASD (e.g. tuberous sclerosis or Fragile X syndrome), or an IQ below 70. We also excluded participants who were reliant on receiving regular medication known to directly modulate glutamate and GABA systems. However, we included participants on other medications which are commonly prescribed in ASD: one person with ASD who took a single dose of Ritalin on the morning of each study visit, and one person with ASD who took a single dose of sertraline on the morning of each study visit. We asked participants to abstain from using cannabis and/or other illicit substances in the month prior to scanning, and from drinking alcohol on the day prior to testing. We also carried out Urine Drug Screening on each test day. Data from individuals who screened positive for these substances were excluded. Thus, we initially retained data from 34 subjects (neurotypical control n = 17, ASD n = 17) (see Table 1 for demographics); this sample size was sufficient to detect a 10% E-I shift (where ‘shift’ means a change in a component of the Glx-GABA metabolite pool) at a power of 0.8 and a significance level of α = 0.05, based on a power analysis using previous findings in the department [19]. All participants had an IQ over 70. All participants in the ASD group had a clinical diagnosis of ASD made according to ICD10 research criteria [24,25,26], and severity of symptoms was confirmed using standardised research diagnostic instruments (Autism Diagnostic Observation Schedule, ADOS; and Autism Diagnostic Interview-Revised, ADI-R).

Imaging data acquisition

All imaging data were acquired on a 3T GE Excite II magnetic resonance imaging (MRI) scanner (GE Medical Systems, Milwaukee, WI, USA). The scanning protocol included a structural MRI scan acquired using a 3D inversion recovery prepared fast spoiled gradient recalled (IR-FSPGR) sequence (slice thickness = 1.1 mm, spatial positions = 124, flip angle = 20°, field of view (FoV) = 280 mm, echo time (TE) = 2.844 ms, repetition time (TR) = 7.068 ms, inversion time = 450 ms, matrix = 256 × 256). This structural scan was conducted to obtain information used during the preprocessing of the spectroscopy scan. The scanning protocol further included a spectroscopy scan based on the MEshcher-GArwood Point RESolved Spectroscopy (MEGA-PRESS) sequence [27]. We acquired data (44 averages) from two voxels: the first was positioned in the BG (echo time (TE) = 68 ms, repetition time (TR) = 1800 ms, voxel size = 35*30*25 mm 3 ).

This voxel was placed with the anterior border initially abutting the anterior portion of the left lentiform nucleus, and as medial as possible, to avoid the ventricles as much as possible. Thus, taking into account slight inter-individual anatomical differences, this voxel was on average composed as follows: the white matter (WM), primarily included the internal capsule and part of the corpus callosum. The grey matter (GM), included the BG [

55%], the thalamus [

25%] and the insula [

The second voxel was positioned in the DMPFC (TE = 68 ms, TR = 2000 ms, voxel size = 25*40*30 mm 3 ). This voxel was placed in the midline, avoiding the corpus callosum. Resultantly, given inter-individual variance, this voxel was composed as follows: the WM included the corpus callosum and cingulum; while the GM included the anterior part of the cingulate gyrus.

Representative voxel positions are shown in Fig. 1.

Magnetic resonance spectroscopy (MRS) representative voxel placement and example spectra. a MRS voxel of interest (outlined in white) in the basal ganglia and the dorsomedial prefrontal cortex. b Example spectroscopy spectra from each voxel. Glx glutamate + glutamine, GABA + γ-aminobutyric acid + macromolecules, NAA N-acetyl-aspartate, p.p.m parts per million

Urine test

To evaluate presence or absence of illicit substances that could confound potential effects of the pharmacological probes tested in this study, we performed liquid chromatography-mass spectrometry (LC-MS) analysis on urine samples provided by each participant before the drug administration. Participants that showed positive results for any of the drugs tested, including Amphetamines (Amphetamine, Methamphetamine, MDMA/Ecstasy), Benzodiazepines, Cannabis, Cocaine (as benzoylecgonine), Methadone and its metabolite EDDP, and Opioids (6-Monoacetylmorphine, Morphine, Codeine, Dihydrocodeine), were excluded from the analysis, resulting in the exclusion of four subjects (two controls, two ASD) from the original sample.

Data processing

Structural data processing

T1-weighted structural MRI volumes were inspected manually to ensure adequate signal-to-noise ratio (SNR) and absence of motion artefacts. Subsequently, structural volumes were normalised to Montreal Neurological Institute (MNI) space, and segmented into GM, WM, and CSF, to obtain percentage measures of tissue composition in each individual MRS voxel, using positional coordinates embedded in the raw spectra data files.

MRS data processing

MRS data were pre-processed using in-house scripts adapted from FID-A [28], which prepared the data for reading into the main processing software. This included conversion of data to the required file format, combination of receiver channels, removal of ‘bad’ averages (>4 standard deviations), frequency drift correction (alignment of averages), separation and visualisation of the edit on/off spectra, and their subtraction to generate the difference spectrum. Each spectrum was manually inspected to ensure adequate SNR, as well as the absence of artefacts [26, 28]. Representative example spectra are displayed in Fig. 1.

MRS data were then processed using LCModel v6.3-1 L software (Stephen Provencher Incorporated, Oakville, Canada). LCModel uses a linear combination of model spectra derived from metabolite solutions in vitro to analyse the major resonances of in vivo spectra. For this analysis, we used a basis set (mega-press-3T-1) to determine the concentrations of GABA+ (which comprises GABA plus macromolecules), glutamine, glutamate, glutathione (GSH), N-acetyl-aspartate (NAA), N-acetyl-aspartylglutamate (NAAG), NAA + NAAG, Glx (Glu + Gln), and GSH + Glu + Gln in each voxel; however, for this analysis, we focused solely on GABA+ and Glx.

In MRS, partial volume effects (different proportions of GM, WM, and CSF in the MRS voxels) are a potential confound, especially given previously reported volumetric differences between autistic and neurotypical individuals [29]. To account for partial volume effects, we therefore corrected all metabolites for GM, WM, and CSF percentages. Assuming that CSF only contains negligible quantities of the metabolites of interest, the calculations were as follows: LCModel assumes a voxel is 100% WM with a water concentration (WCONC) of 35880 mM and corrects each metabolite value (where F stands for fraction) using the factor: (43300*FGM + 35880*FWM + 55556*FCSF)/(1-FCSF). To correct for the value of water concentration being used in the processing through LCModel, we divided values by an individual correction factor (35880), arriving at (1.207*FGM + FWM + 1.548*FCSF)/(1-FCSF). Therefore, in summary, the corrected metabolite values were obtained by multiplying the raw metabolite values by this correction. Since we did not measure relaxation times for tissue water and metabolites, these were not corrected for—with the exception of assuming the tissue water relaxation time (T2 = 80 ms) [30].

To further ensure the robustness of our findings, we excluded all measurements of GABA+ and Glx (Glx = glutamate + glutamine) where the LCModel Cramér-Rao lower bound (CRLB) estimates exceeded 15% from further analysis (LCModel manual, Stephen Provencher Incorporated, Oakville, Canada). This resulted in the exclusion of a total of eleven data points from six ASD participants from the original sample. The spread across voxels and conditions (placebo/CBD) was as follows: 1: BG GlxPLC; 2: DMPFC GABA + PLC & GlxPLC; 3: DMPFC GABA + CBD & GlxCBD; 4: DMPFC GABA + CBD & GlxCBD; 5 (also excluded due to positive drug screening): DMPFC GABA + PLC & GlxCBD; 6: DMPFC GlxCBD & GABA + CBD.

Statistical analysis

Demographic measures (age, IQ) and baseline levels of Glx and GABA+ in each region of interest were compared using a one-way ANOVA (significance level p < 0.05).

To test the primary hypothesis that CBD impacts on E-I balance in our two brain regions of interest (BG and DMPFC), differences in mean metabolite concentrations were calculated using two 2 × 2 × 2 mixed-model ANOVAs with group (neurotypicals, ASD) as between-subject factor, voxel (BG, DMPFC) and drug (PLC, CBD) as within-subject factors, and the respective metabolite (Glx, GABA+) as the dependent variable. Our planned comparisons tested a priori predictions that CBD would impact upon Glx and GABA+; and that there would be differences in the response of participants with and without ASD. With the caveat that Bonferroni testing can be overly conservative, for completeness however, we also report a Bonferroni corrected p-value alongside any significant (uncorrected) results.

However, this repeated-measures approach is impacted by missing data (one missing/poor quality data point from either voxel during either placebo or drug condition results in data from that individual being omitted); also there is a possibility that our results were influenced by the different T1-weighting in the cortical and subcortical voxels. Therefore, following this overall analysis we conducted secondary post hoc two-by-two mixed-model ANOVAs with group (neurotypicals, ASD) as a between-subject factor, and drug (PLC, CBD) as a within-subject factor for each metabolite in each region separately and examined any group difference in the change in each using as much of the available data as possible. Thus, for Glx measures in both BG and DMPFC, ASD n = 13, neurotypicals n = 17; for GABA+ measures in the DMPFC, ASD n = 11, neurotypicals n = 17; and for GABA+ measures in BG, ASD n = 16, neurotypicals n = 17.

All analyses were performed using SPSS 24.00 software (SPSS, Chicago, IL, USA). Graphs displaying results were produced using GraphPad Prism version 7 for Mac, GraphPad Software, La Jolla, CA, USA, www.graphpad.com.



Groups did not differ significantly in age (F(1) = 0.956, p = 0.335); but, as is commonly reported, individuals with ASD had a slightly lower IQ than neurotypical controls, and this difference was significant (F(1) = 5.781, p = 0.022) (as summarised in Table 1). Therefore, to be sure that our findings were not influenced by IQ, we investigated the relationship between drug-induced shifts (CBD-PLC) in metabolite levels (Glx and GABA+) and IQ. As expected, there were no significant correlations across the whole group (r < 0.095, p > 0.350), in ASD alone (r < −0.008, p > 0.698) nor in the neurotypicals alone (r < 0.068, p > 0.235), suggesting that the difference in IQ did not influence the results. No participant experienced any subjective or objective ill-effects/harm following administration of the study drug.

Tissue composition and data quality

Tissue percentage (not excluding omitted spectra) differed between groups for BG PLC GM (F(1) = 7.307, p = 0.011) and for BG PLC WM (F(1) = 9.345, p = 0.004), but not for other tissues or drug conditions (as summarised in Table 2). This is unsurprising, as previous studies have suggested morphological differences in the BG in autistic compared to neurotypical individuals [31]. In our statistical analysis we corrected all metabolite values accordingly.

To ensure that the [H]MRS data quality was equal between groups, we compared CRLB estimates for each metabolite (Glx, GABA+) in each voxel (excluding omitted spectra), using a one-way ANOVA. As expected, we found no significant differences (all F(1) ≤ 4.102, all p ≥ 0.052) (as summarised in Table 3).

In extended MRS studies, there is often a risk of ‘drift’, where the metabolite estimates on the same scanner change over long periods of time. For this reason, we compared the duration between scans (days between PLC and CBD scan) across the two groups. There was no significant difference in duration between visits (F(1) = 0.041, p = 0.841) in controls (34.82 ± 24.99) and ASD (36.44 ± 20.53) (see Table 1). Furthermore, scan date for each drug condition (PLC, CBD) was not correlated with the value of any metabolite at that drug condition (all Pearson’s r ≤ 0.299, all p ≥ 0.115), confirming that data acquisition was stable over time.

Metabolite differences

Glx (glutamate+glutamine)

There were no significant between-group differences in baseline Glx in the BG (F(1) = 0.000, p = 0.993, n = 29) or in the DMPFC (F(1) = 0.196, p = 0.661, n = 32). There was however a significant voxel × drug interaction effect (F(1,21) = 5.235, puncorr = 0.033, partial eta squared (η 2 ) = 0.200): in both groups, CBD increased Glx in the BG and decreased Glx in the DMPFC (as depicted in Fig. 2). This effect did not survive stringent Bonferroni-correction. Nonetheless, pcorr = 0.126 indicates at least an 87% likelihood that the observed effect was real.

Glx (glutamate + glutamine) (14 neurotypicals, 9 autistic individuals) (a) and GABA+ (γ-aminobutyric acid + macromolecules) (16 neurotypicals, 8 autistic individuals) (b) in the basal ganglia and the dorsomedial prefrontal cortex for both groups in both drug conditions. Glx (a) and GABA+ (b) concentration represents the ratio of the Glx and GABA+ metabolite resonance area to the unsuppressed water resonance area, respectively. Dotted lines connect group means, which are indicated by black horizontal bars. Error bars represent standard deviations. ASD autism spectrum disorder, BG basal ganglia, CBD cannabidiol, DMPFC dorsomedial prefrontal cortex, PLC placebo, TD typically developed controls; * indicates a significance level at p ≤ 0.05; *** indicates a significance level at p ≤ 0.001

Results of post hoc testing within each voxel separately were consistent with these findings, albeit at trend level. In the BG, CBD increased Glx in both groups (F(1,24) = 3.593, puncorr = 0.070, η 2 = 0.130); in the DMPFC, CBD decreased Glx in both groups (F(1,26) = 4.030, puncorr = 0.055, η 2 = 0.134). Thus, differences in the acquisition parameters for each region were unlikely to explain the overall results. Moreover, post-hoc within-subject comparisons of Glx changes (CBD-PLC) showed that there was no group-difference in Glx responsivity to CBD in the BG (F(1) = 0.602, puncorr = 0.445) nor in the DMPFC (F(1) = 0.006, puncorr = 0.937), confirming that Glx in adults with and without ASD responded to CBD in the same way.

There were no significant between-group differences in baseline GABA+ in the BG (F(1) = 0.000, puncorr = 0.987, n = 33) or in the DMPFC (F(1) = 0.408, puncorr = 0.528, n = 30). There was however a significant group × drug interaction in both brain regions (F(1,22) = 13.506, puncorr = 0.001, η 2 = 0.380). CBD increased GABA+ in the control group and decreased GABA+ in autistic individuals. This effect survived Bonferroni-correction (pcorr = 0.004). These findings are displayed in Fig. 2.

Post hoc testing in each voxel separately indicated that this result was largely driven by changes in the DMPFC, where there was a significant group × drug interaction effect (F(1,23) = 4.864, puncorr = 0.038, η 2 = 0.175); and the group difference in CBD-induced change in GABA+ was significant in the DMPFC (F(1) = 6.510, puncorr = 0.017), but not in the BG.

Post hoc within-subject analyses of GABA+ changes (CBD-PLC) also confirmed a significant group difference in the DMPFC (F1) = 4.864, puncorr = 0.038), and but not the BG. This effect did not survive stringent Bonferroni-correction (pcorr = 0.14), but there was at least a 86% chance (pcorr = 0.14) it was real.

Finally, given that we excluded ASD participants, but not neurotypicals, on the basis of low CRLB estimates, we also reran our analysis including CRLB measures as a covariate and this did not materially alter the findings. Thus, GABA+ in adults with and without ASD responded to CBD in opposite directions, and especially in the cortex.

We note that secondary analyses confirmed that CBD did not alter the levels of other metabolites within the spectrum; namely we observed no significant group and drug main effects, and no group × drug interaction effects for GSH, NAA, NAAG, NAA + NAAG, and GSH + Glx.


Here we report that acute (single dose) CBD ‘shifts’ levels of the brain’s primary excitatory and inhibitory neurotransmitters in adults with and without ASD. In both groups, CBD increased Glx in the BG voxel and decreased it in the DMPFC voxel. In contrast, CBD had opposite effects on GABA+ in each group. Specifically, both in prefrontal and subcortical regions, CBD increased GABA+ in the controls but decreased GABA+ in ASD. Moreover, in line with some [19, 21], but not all previous MRS studies of glutamate and GABA in ASD [21, 32] in the BG and DMPFC voxel, there were no differences in baseline metabolite levels. Thus, our study suggests that excitatory (E) glutamate response mechanisms to CBD are comparable regardless of diagnosis; whereas inhibitory (I) GABA response pathways are altered in ASD.

Effect of CBD on Glx

The region including and surrounding the BG is richly innervated by a web of excitatory pyramidal neurons alongside GABAergic inhibitory projection neurons and glia cells [33]. The increase in Glx triggered by CBD in both groups could therefore have resulted from CBD binding to neuronal TRPV1 receptors. Subsequent activation of pyramidal neurons [15] may potentially have contributed to the altered Glx metabolite levels in the BG captured by MRS. Cannabinoid activation of TRPV1 receptors on microglia could also theoretically upregulate microglial activity and migration, leading to extracellular vesicular shedding and augmentation of Glx levels [34]. However, this is speculative, given the rapid desensitisation of TRPV1 receptors after activation [35].

In the DMPFC, glutamatergic pyramidal neurons predominate, with relatively fewer GABAergic interneurons (ratio

4.7:1) [17]. Here, CBD reduced Glx in each group. One possible explanation for this is that CBD suppressed the activity of prefrontal glutamatergic neurons via their 5-HT1A receptors [17, 18], thereby reducing Glx levels. Preliminary evidence has linked impaired TRPV1 signalling to the ASD risk gene SHANK3, and 5-HT anomalies, including 5-HT1a receptor dysfunction, to ASD [36]. Despite this, we found no group difference in Glx response to CBD. This implies that glutamate targets of CBD in the BG and DMPFC in idiopathic ASD are no different from those in neurotypicals.

Effect of CBD on GABA+

In contrast, CBD increased GABA+ levels in the BG and DMPFC voxel in neurotypicals, but decreased GABA+ levels in the BG and (markedly so) in the DMPFC voxel of autistic adults. The causes of group differences in GABA+ response are unknown. However, it may be partially explained by ASD-related alterations in CBD targets. For example, the expression of the CBD interneuron GPR55 receptor is reduced in the cortex in the valproic rat model of ASD [37]. Another explanation could be more general disruption to GABA pathways in ASD. For instance, a reduction in the activity of the rate-limiting GABA synthesising enzyme glutamic acid decarboxylase (GAD) [38], and genetic anomalies in GABA receptors [39] have been reported in ASD. Since MRS GABA+ is thought to reflect metabolic (intracellular) and extracellular GABA+ levels, rather than GABAergic synaptic transmission [40, 41], further studies are required to back-translate our results into preclinical models to dissect exactly what underpins the atypical cortical and sub-cortical GABA+ response to CBD in ASD; and what is the impact on excitatory and inhibitory system activity. For example, Kaplan and colleagues have reported that CBD appears to restore GABAergic neurotransmission in an animal model of Dravet syndrome [14]. Despite the limitations of resolution using MRS, the present findings, together with our previous finding of atypical prefrontal GABA responsivity to the glutamate-GABA acting drug riluzole, clearly point to an alteration in the dynamics of GABA, but not glutamate, systems in ASD. This observation may not only have aetiological relevance, but also add to the evidence that the GABA system may be a tractable treatment target in ASD [42, 43].

Cortico-striatal systems (in ASD)

The CBD-induced shift in cortical and subcortical Glx and GABA+ levels may influence excitation and inhibition, although MRS does not tell us directly about excitation or inhibition at the level of the synapse. Nevertheless, this shift in metabolites could potentially have widespread implications for brain function and behaviour. This is because the BG (and the thalamus and insula) and DMPFC form part of a circuit that is heavily dependent on glutamatergic excitation and GABAergic inhibition and supports and regulates a range of cognitive processes. In brief, in the neurotypical brain, the BG receive input from the (insular) cortex, brainstem, and thalamus. Cortical input is predominantly excitatory [44], but BG output nuclei act via a direct monosynaptic GABAergic and an indirect polysynaptic glutamatergic pathway [45]. Projection neurons from the output nuclei provide GABAergic tonic inhibition to thalamocortical and brainstem neurons to complete a ‘loop’ [45, 46]. In ASD, however, neuroimaging studies have revealed reduced WM ‘integrity’ especially in prefrontal tracts [47], and abnormal ‘functional integration’ of the BG and the DMPFC. This is thought to partly explain why multiple processes dependent upon cortico-striatal loop integrity, such as socio-emotional, motor, and reward processing, are altered in ASD [48, 49]. Our results suggest that the structural and functional differences previously reported in MRI studies of cortical-subcortical systems in ASD extend to atypical E-I response to pharmacological challenge.


The corollary of our observations is that because CBD ‘shifts’ glutamate and GABA+, it may affect glutamatergic excitation and GABAergic inhibition, and thereby impact on brain function. We did not directly test this here, but some support for this proposition comes from a recent report that CBD increases prefrontostriatal functional connectivity in neurotypical controls [50]. However, our results predict that the direction of a functional response to CBD may be distinct in autistic individuals, and this warrants further investigation.

Our results reinforce the fact that we cannot expect the actions of a drug tested in a typically developing population to be replicated in people with neurodevelopmental conditions. For example, we have previously reported a link between disrupted functional connectivity and an atypical MRS GABA+ response to pharmacological E-I challenge through riluzole in ASD but not in controls [19]. However, unlike CBD, riluzole increased prefrontal GABA+ in ASD. Together with our current findings, this suggests that GABA+ can be shifted bi-directionally in cortical-subcortical systems in adults with ASD. This is encouraging, as we can now begin to build a repertoire of drugs that elicit a biological response in ASD. This tactic will be critical given the heterogeneity of the autism spectrum, where a ‘one-drug-fits-all’ approach is unlikely to succeed. Thus, our next steps will be to examine whether acute drug response allows us to (i) identify more pharmacologically homogeneous sub-groups within ASD; and (ii) predict clinical responsiveness to sustained treatment.


We acknowledge that our study has important limitations. First, here we measured MRS bulk amounts of Glx and GABA+ in the chosen voxels of interest. This did not allow us to reliably discern the specific contributions of different compounds (glutamate and glutamine) contributing to the Glx signal. Moreover, at 3T, we were limited to draw inferences about intra-cellular and extra-cellular metabolite levels from our findings. Future studies with higher resolutions and magnetic field strengths are required to address these questions.

Second, we only included adult male subjects with an IQ above 70, and with no epilepsy or comorbid psychiatric conditions. This step was taken to ensure the homogeneity of our study sample and to make sure that observed effects were related to ASD rather than a comorbidity of ASD. However, this also limits our ability to extend our findings to the general ASD population, which is characterised by heterogeneity and the presence of psychiatric and neurological comorbidities. Future studies should attempt to replicate our findings in larger and more diverse population samples, and especially include women.

Third, our participant sample was relatively small. This can be attributed to our strict recruitment criteria (e.g. no use of illicit substances in the month leading up to and during the study). It is also influenced by difficulties inherent in time-intensive repeated-measures studies involving drug administration, e.g. high drop-out rates. Finally, also contributing to the modest sample size were our rigorous data quality criteria, e.g. exclusion of scans based on head motion, known to be a difficulty in ASD. That said, our sample size was comparable (or bigger than) previous MRS studies in ASD [19, 21]. Moreover, each individual in our study had two scans and thus acted as their own ‘control’ to reduce inter-subject variability and to increase statistical power.

Fourth, in this study we only investigated the impact of acute CBD administration on brain. We cannot extrapolate from the effects of a single dose to the impact of repeated administrations, e.g. as a therapeutic option in ASD, for several reasons. For instance, chronic CBD administration may result in a steady state, wherein the brain system plasticity equilibrates to the presence of CBD. Future studies should thus investigate the impact of long-term treatment with CBD on brain and behaviour.


In summary, we report that CBD can ‘shift’ levels of Glx and GABA+. These metabolites contribute to the regulation of excitatory and inhibitory neurotransmission in both the typical and the autistic brain. However, our study also demonstrated that the atypical (autistic) brain reacts differently to CBD challenge of GABA+. Our findings that the GABAergic system is distinct in ASD, but can be shifted, is relevant both to our understanding of causal mechanisms and to the discovery of treatment targets in ASD. Additional studies will be required to (i) identify the neural basis of the response to acute CBD challenge, including potential pharmacologically homogeneous sub-groups within the autistic spectrum; (ii) examine potential functional consequences of CBD challenge in terms of inhibition, brain network activity, cognition, and behaviour; and (iii) investigate whether an acute response to CBD could predict the effects of sustained treatment in ASD.


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Funding and disclosure

This study was an Investigator Initiated Study (G.M.) which received funding and product from GW Research Ltd (Cambridge, UK). GW Research Ltd (Cambridge, UK) had no role in the data collection or analysis of results, nor in the decision to publish. The authors also acknowledge infrastructure and training support from the National Institute for Health Research (NIHR) Mental Health Biomedical Research Centre (BRC) at South London and Maudsley NHS Foundation Trust and King’s College London. The views expressed are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health, U.K. Additional sources of support included the Sackler Institute for Translational Neurodevelopment at King’s College London, Autistica, the Medical Research Council (MRC) Centre grant (MR/N026063/1) and EU-AIMS (European Autism Interventions)/EU AIMS-2-TRIALS, a European Innovative Medicines Initiative Joint Undertaking under Grant Agreements No. 115300 and 777394, the resources of which are composed of financial contributions from the European Union’s Seventh Framework Programme (Grant FP7/2007–2013). RAEE receives salary support from NIH R01 MH106564 and U54 HD079123. The remaining authors have nothing to disclose. Finally, the authors sincerely thank all the participants.

Author information

These authors contributed equally: Declan G. M. Murphy, Eileen Daly, Gráinne M. McAlonan


Department of Forensic and Neurodevelopmental Sciences, Institute of Psychiatry, Psychology & Neuroscience, King’s College London, London, UK

Charlotte Marie Pretzsch, Jan Freyberg, Bogdan Voinescu, Jamie Horder, Maria Andreina Mendez, Robert Wichers, Laura Ajram, Declan G. M. Murphy, Eileen Daly & Gráinne M. McAlonan

Department of Neuroimaging Sciences, Institute of Psychiatry, Psychology & Neuroscience, King’s College London, London, UK

David Lythgoe & Steven Williams

South London and Maudsley NHS Foundation Trust Pharmacy, London, UK

Glynis Ivin & Martin Heasman

Russel H Morgan Department of Radiology and Radiological Science, Johns Hopkins Medical Institutions, Baltimore, MD, USA