EducationHow does cannabis affect mental health?

How does cannabis affect mental health?

10 min read

Kerry Charron

How does cannabis affect mental health?


Medicinal cannabis finally became a reality here in the UK back in November 2018. Let’s quickly look at some of the general facts relating to medical cannabis in the UK, as of right now. 

A recent research report, the largest of its type ever conducted in the UK, showed that up to 46% of UK adults suffering from a condition that may be potentially treated with medical cannabis still do not have access to it, and live with significant discomfort. 

In fact, 99% of potentially eligible patients are believed to have been unsuccessful in securing a prescription through the NHS so far. Even more surprising is the fact that upwards of 16.5 million UK adults still believe that medical cannabis is illegal. 

One potential explanation for the limited adoption of medicinal cannabis is its nearly century-long prohibition, which has resulted in its demonization and, to a certain extent, an unfounded association with negative mental health outcomes. While an increasing number of studies show that cannabis has the potential to effectively manage anxiety, stress, and other mood disorders, it is also associated with an increased risk of psychiatric disorders.

This article will provide a brief overview of the history of cannabis in the United Kingdom, as well as the research trends regarding mental health.

A brief history of cannabis in the UK

Up until the introduction of the 1928 Drugs Act, which made cannabis cultivation and use illegal, the plant was often taken for medicinal and recreational purposes here in the UK. For large periods in our history, hemp (a subspecies of cannabis sativa L.) was one of the cornerstones of industry and was a legally required crop for all farmers during the reign of both Henry VIII and Elizabeth I. This was to help ensure that the naval supremacy that the UK held was protected, as all ships needed strong ropes and sails made from hemp. 

In 1971 cannabis was classified as a Class B drug as part of the Misuse of Drugs Act. Under this act, Class A substances are classified as the most harmful and Class C as the least. In 2004, the classification was downgraded to Class C drug with less severe penalties, but this decision was reversed in 2009. 

This law stipulates that the penalty for cannabis possession or any Class B substance can be a prison sentence of up to 5 years. Illegal cultivation and sales of cannabis can result in up to 14 years in prison. Both violations can come with an unlimited fine. These days, people caught carrying less than an ounce (28 grams) of cannabis will most often face a fine, while possession of larger quantities can still result in imprisonment.

Medical cannabis was legalized in November 2018. This was a huge step towards improving the lives of patients with qualifying conditions. However, despite the change in legislation, there are still significant barriers and challenges when it comes to accessing medical cannabis. NHS doctors are somewhat handcuffed in offering prescriptions, and are only legally able to provide patients suffering from three specific conditions with cannabis-based medical products. These three conditions are multiple sclerosis, chemotherapy-related nausea and vomiting, and severe treatment-resistant epilepsy. Fortunately, private medical cannabis clinics, and the specialists that work with them, are able to prescribe medical cannabis for a wider range of conditions.

How does cannabis affect mental health?

Extensive research indicates that cannabis has a complex relationship with mental health, as its effects can differ significantly based on various factors. These factors include the individual's age, genetics, mental health history, frequency of use and dosage size, as well as the specific strain and cannabinoid composition involved. 

While some people may experience positive outcomes such as reduced symptoms of anxiety and depression, pain relief, and others may encounter adverse effects such as increased anxiety, paranoia, or even potential exacerbation of existing mental health conditions. Understanding these intricate dynamics is crucial in evaluating the overall impact of cannabis on mental well-being.

Let's dive into the belly of the beast and see what the research has to say.

The positive effects of cannabis on mental health

The ever-growing body of clinical research into this fascinating plant shows that it has the potential to ease the symptoms associated with anxiety and depression, while also promoting a sense of calm and relaxation. Cannabis also offers a range of potential physical benefits, including muscle relaxation, sleep enhancement, appetite stimulation, and nausea reduction – all of which may help ease the burden of mental health issues. 

While there have been suggestions that cannabis may increase the risk of certain mental health conditions, a recent study found no association between cannabis potency and increased risk of psychosis. Now that the medical cannabis 'revolution' is underway and the stigma is slowly fading, we can look forward to more rigorous research into this area, and a clearer understanding of both the potential benefits and risks of cannabis on mental health.

With that said, the currently available evidence is already providing us with some promising insights.

Medical cannabis treatment may be effective at lessening anxiety and depression symptoms for many people. Low-THC cannabis appears to minimize negative feelings, but this action seems to diminish as the dose rises. When it comes to CBD, all dosage sizes have been shown to potentially lower rates of anxiety and depressive symptoms. 

In one study, titled Cannabidiol in Anxiety and Sleep: A Large Case Series”, it was shown that a range of doses produced a reduction in anxiety scores and improved sleep quality for those suffering from anxiety-related insomnia. The study involved 72 adults who presented with symptoms of either anxiety or poor sleep. Within the first month, anxiety scores decreased in nearly 80% of the patients and remained lower throughout the duration of the study. Sleep scores showed improvement in over 65% of the patients within the first month, although it should be noted that this varied over time.

Another study looked into the effectiveness of CBD in treating subjective anxiety brought on by public speaking. This clinical trial showed that both 300 mg and 600 mg of CBD were effective in reducing anxiety among participants. Participants that were given the 300 mg dose reported much lass anxiety after the public speaking task, and for those that were given 600 mg, "a significant reduction in anxiety-related measures obtained during their speech performance was observed'

When it comes to more serious mental health issues, such as PTSD, medical cannabis is also showing signs of being an effective complementary treatment option, in particular CBD. This 2019 study, while only small in scale (11 subjects), found that over 90% of the patients showed a decrease in PTSD symptoms within 8 weeks of treatment with CBD. The study also notes that "CBD also appeared to offer relief in a subset of patients who reported frequent nightmares as a symptom of their PTSD." and that "CBD was generally well tolerated, and no patients discontinued treatment due to side effects."

The negative effects of cannabis on mental health

As with all mind-altering substances, cannabis does have the potential to cause some negative effects on mental health. This is certainly not the case for everyone, and as long as cannabis is taken responsibly and in moderation, these risks are minimal.

This is especially true when considering medical cannabis. Medical cannabis is specifically tailored to provide therapeutic benefits under the supervision of medical professionals and can minimize any potential negative effects on mental well-being. However, it is still essential to be aware of the risks that may arise.

We mentioned earlier that there is a possible to be a link between high-THC cannabis and an increased risk of psychosis.

A 2009 study which collected information on cannabis use from 280 cases found that there may be a link between heavy cannabis use and an increased risk of psychotic episodes, with the paper concluding "People with a first episode of psychosis were more likely to be current daily users of cannabis and to have smoked cannabis for more than 5 years."

But these findings have been called into question by newer research.

In a 2023 paper, researchers found no significant link between cannabis use and increased risk of developing psychosis. This cross-sectional study of 410 participants concluded that "No association was found between high potency cannabis preference or THC concentration in cannabis and psychosis-like symptoms".

But the paper goes on to state that "High potency cannabis use was associated with a slight increased risk of cannabis dependence" and that "Weak evidence suggested a small association between cannabis potency and depression and anxiety"

Neither of these findings should come as a surprise, as with any substance, administering it frequently and in high doses has the potential to lead to dependence and other negative side effects. High THC potency does seem to play a role in feelings of anxiety and depression, so if you are interested in taking cannabis-based medical products for mental health issues, it is essential to seek the guidance and advice of a medical professional to determine the appropriate dosage and product type for your specific needs.

The bottom line

So, there we have it. An overview of the current research on the link between cannabis and mental health. While the field of medical cannabis research is still somewhat in its infancy, and there is still much to be discovered and understood, it is clear that cannabis has potential as a treatment for certain mental health conditions. However, like any form of medication or therapy, it should only be taken under the supervision and guidance of medical professionals.

Mental health is such a complex and sensitive issue, and it is essential to approach treatment with caution and care. Medical cannabis should never be seen as a miracle cure or taken without careful consideration and consultation with doctors and mental health professionals. Do not think of it as a replacement to your current treatment plan, but rather as a potential complementary option. As always, the most important thing is to prioritize your well-being and work closely with your clinical care team to find the best solution for you. Remember, every patient is unique and may respond differently to medical cannabis.

If you, or a loved one, would like to learn more about the available medical cannabis approaches, Releaf is here to help. We understand the potential that medical cannabis offers in treating a wide range of medical conditions. With our tailored monthly packages, specialist consultations for medical cannabis, and a unique medical cannabis card for protection, you can access the treatment you require with the support and guidance you need. Don't let the stigma surrounding medical cannabis hold you back from exploring its potential benefits for your mental health.

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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