EducationThe science behind medical cannabis for ADHD

The science behind medical cannabis for ADHD

9 min read

Kerry Charron

The science behind medical cannabis for ADHD


Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental condition that is believed to arise from a complex interplay of genetics, brain structure, and function. While individuals with ADHD often demonstrate high intelligence and creativity, they may encounter challenges in information processing, sustaining attention, and regulating impulsive behaviour.

Conventional approaches, such as pharmaceutical medications and behavioural therapy, have proven to be effective in managing ADHD symptoms. However, some patients are now exploring alternative treatment options, such as medical cannabis, as a potential complementary aid for their condition. This emerging area of research aims to further understand the potential benefits and risks associated with medical cannabis in the context of ADHD management, with the rapidly growing body of evidence suggesting that certain cannabinoids may be useful in symptom management.

What is medical cannabis exactly?

The cannabis sativa L. plant has a long history of medicinal applications stretching back thousands of years. Its first recorded medicinal use appeared in a Chinese text written by Emperor Shen Nung in 2737 BC, and from there we see it pop up throughout ancient cultural and medicinal texts.

This plant is now one of the most studied medicinal plants in modern science and contains a vast array of chemical compounds, known as phytocannabinoids, which interact with the endocannabinoid system (ECS). The ECS is the largest chemical signalling system in the human body, and is responsible for modulating many of the body’s regulatory systems and various physiological processes, including appetite, sleep, mood, inflammation, immune function, and more.

The ECS is made up of:

  • Endocannabinoids, which are naturally occurring cannabinoids produced by the body that interact with cannabinoid receptors
  • Cannabinoid receptors (CB1 and CB2), which are found throughout the body and play a role in regulating various physiological processes
  • Metabolic enzymes, which break down endocannabinoids after they’ve been used.

The cannabinoids produced by cannabis and hemp varieties are structurally similar to endocannabinoids and can interact with these receptors. This is why they are able to produce the wide range of effects on the body that we’ve come to recognize in both recreational and medical cannabis applications.

The current legal status of medicinal cannabis in the UK

Medical cannabis was finally legalised in the UK in November 2018, after decades of lobbying and campaigning from those affected by a range of medical conditions. Before this, the only cannabis-based products legally available in the UK were CBD oil, which is derived from hemp plants grown for industrial purposes and is not considered to be a controlled substance.

Now, with the legalisation of medical cannabis, UK patients have access to a wide range of products with varying ratios of THC and/or CBD, depending on the desired therapeutic outcome. Although these products are still regulated by the Medicines and Healthcare Products Regulatory Agency (MHRA) and can only be prescribed by registered medical practitioners, they are slowly becoming more widely available in the UK.

What is the research saying regarding medical cannabis and ADHD?

Now onto the interesting stuff. Thanks, in large part, to the current wave of both recreational and medicinal cannabis legalisation that is sweeping large parts of the world, the vast therapeutic potential of medical cannabis is slowly being uncovered.

When it comes to ADHD, there are a couple of key studies that we can reference to gain a deeper understanding of this condition, and the role medical cannabis can play in helping control some of the symptoms.

The first study we will highlight comes from 2020, and offers some great insight. The objective of the study was to explore the potential connections between different doses of cannabinoids and terpenes and the symptoms of ADHD in adult patients undergoing medical cannabis treatment.

Hold up, what are terpenes?

Terpenes are the aromatic compounds found in many plants, including cannabis. They govern the smell and flavour of each plant, but they also have therapeutic benefits that have been long overlooked, or at least misunderstood. Terpenes interact with cannabinoids to create a synergistic effect known as the "entourage effect”, which is a key factor in the successful management of ADHD and other medical conditions, and is believed to produce an amplified effect than either cannabinoid alone.

The study had 59 participants, with 18 receiving a low dose (20 – 30 grams) and 35 being offered a higher dose (40 – 70 grams) per month. Surprisingly, the study focuses on a phytocannabinoid that is less studied than THC or CBD, CBN. CBN is a minor cannabinoid that is believed to have sedative effects and an ability to reduce inflammation in the body, but this study proves that it is also capable of modulating the symptoms associated with ADHD.

The authors concluded that:

"High dosage of cannabinol (CBN) was associated with lower ADHD symptom severity, suggesting a possible combination effect in whole-plant medical cannabis treatment." and that "Other phytocannabinoids might be more essential for the effect on ADHD patients".

So, what is the research saying when it comes to THC and CBD?

Well, to be honest, the specific literature is still quite scarce, and any research in this area is currently limited to the anecdotal evidence of patients who are self-medicating with medical cannabis for ADHD.

One paper, which is a qualitative analysis of online forum discussions on cannabis use and ADHD, found that

"Twenty-five (25%) percent of individual posts indicated that cannabis is therapeutic for ADHD, as opposed to 8% that it is harmful, 5% that it is both therapeutic and harmful, and 2% that it has no effect on ADHD"

The paper concludes with

"Despite that there are no clinical recommendations or systematic research supporting the beneficial effects of cannabis use for ADHD, online discussions indicate that cannabis is considered therapeutic for ADHD"

But that's not to say that there is no clinically-backed evidence when it comes to THC and CBD, just that these studies have more to do with the related symptoms of ADHD, rather than the disorder itself.

Unwanted symptoms of ADHD can include anxiety, sleep issues, and difficulty controlling impulsive behaviour. Fortunately, THC and CBD have both been shown to be effective in modulating all of these symptoms, and this has been demonstrated in numerous studies.

This 2010 study found that CBD application reduces anxiety in patients diagnosed with social anxiety disorder, and these findings are backed up by this large-scale case study, which found that almost 80% of participants found that their “anxiety levels decreased significantly” following CBD application.

When it comes to anxiety, THC is a little more complicated. Although it has historically been associated with increased anxiety and paranoia, recent studies suggest that the correct dosage and ratios of THC to CBD can actually reduce levels of anxiety in both recreational and medicinal settings.

This 2017 study, titled "Effects of Marijuana on Mental Health: Anxiety Disorders", suggests that low doses of THC can provide a subjective sense of anxiety relief. Conversely, higher doses have been found to amplify negative emotions.

Does medical cannabis come with any risks or side effects?

Yes, like any drug or medication, medical cannabis does come with some risks. The most common side effects of medical cannabis are headaches and dizziness, but these can usually be avoided by starting at a low dose and slowly increasing the dosage over time.

Other side effects include:

  • Nausea and vomiting
  • Dry mouth
  • Increased heart rate or palpitations
  • Drowsiness and fatigue
  • Cognitive impairment, including short-term memory loss
  • The potential for increased anxiety and paranoia with high doses of THC
  • Elevated blood sugar levels (in diabetic patients)

It's important to note that these side effects are typically caused by the THC content of the cannabis, so if you're looking to avoid them altogether, you can opt for a CBD-heavy strain.

CBD does have the potential to interact with certain medications, so it's always best to do your own research and consult with your medical professional before starting a new course of treatment.

How to receive a prescription for medical cannabis for ADHD

Here in the UK, the NHS only prescribes medical cannabis for a small handful of conditions, and ADHD is not on that list. However, it is possible to get medical cannabis prescribed for ADHD through a private medical cannabis healthcare provider.

Releaf is just one of a growing list of providers who offer medical cannabis consultations and prescriptions for those seeking treatment. We provide a comprehensive service, offering informative advice from our team of specialist doctors (all of whom are registered to prescribe medical cannabis), tailored monthly packages to help you find the right option for your specific needs and a unique medical cannabis card which offers protection when receiving legal a medical cannabis prescription in the UK.

If you're looking to get a prescription for medical cannabis for ADHD, and want the assistance of an experienced medical cannabis provider, Releaf is here to help. We understand that medical cannabis can be a daunting prospect if you've never been prescribed it before, but rest assured that our team are experienced and knowledgeable when it comes to prescribing the right products for your specific needs.

It is important to seek medical advice before starting any new treatments. The patient advisors at Releaf are available to provide expert advice and support. Alternatively, click here to book a consultation with one of our specialist doctors.

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Kerry, with experience as a medicinal cannabis cultivation technician and expertise in business licensing applications, is passionate about developing educational content and advocating for better access to medical cannabis worldwide.

Our articles are written by experts and reviewed by medical professionals or compliance specialists. Adhering to stringent sourcing guidelines, we reference peer-reviewed studies and scholarly research. View our editorial policy.

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Further reading

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Medical cannabis on holiday: The basics

Here at Releaf we understand that holidays should be about relaxation, but travelling with medical cannabis sounds like a stressful voyage. We’re doing what we can to absorb that stress so that you can soak up the sun, and so, we’ve designed a series of articles to cover the subject: medical cannabis on holiday. 

Lucy MacKinnon

How long does it take to feel the effects of THC oil?

The time it takes for you to feel the effects of THC depends on the methods of administration as well as your own physiology. Fortunately, there are fast and slow-acting options, as well as ways to take low or high doses in order to facilitate control over the way your body reacts to your medicine.

Editorial Team