By RQS Editorial Team

Perhaps no other branch of cannabis medicine gropes in the dark like that which studies the effect of cannabinoids on a “malfunctioning” human brain.

Today, there is no evidence that cannabis use causes chronic brain disorders, although the complexity of the human brain makes it hard to understand if cannabinoids could instead be effective in treating mental illnesses. When consumed in large doses, cannabis might lead to “psychotic symptoms”, particularly in vulnerable individuals with a personal or family history of mental illness. Yet, a large number of patients with schizophrenia, paranoia, bipolar disorders, and other mental conditions have been self-medicating with cannabis for years.

Doctors in the US who prescribe large amounts of medical cannabis report that very little of it goes to patients with severe psychiatric conditions—with post-traumatic stress disorder being the most common accepted condition. Psychiatrists often advise against cannabis use, while some approve it as a complementary treatment for patients with specific symptoms or diagnoses. Numerous patients report that cannabis relieves some of their symptoms, yet the clinical literature is still underdeveloped, and many studies on the therapeutic use of cannabis for mental health conditions are not of a methodologically high quality.


The role cannabis plays in current psychotherapeutic practices is indeed a complex one. Many patients already feel a sense of stigma surrounding their mental condition, with cannabis only adding fuel to the fire. Healthcare personnel of any level have a duty to protect patients’ private information, and they are not supposed to judge patients’ lifestyles. Conversely, a frank discussion on cannabis use even before starting sessions with a new therapist is highly recommended to help clarify each other’s position regarding the plant.

Therapy should be an opportunity to put oneself out in the open in the company of a caring professional. Any therapist worth their salt should be open to understanding your relationship with cannabis before making any judgment calls. Especially given that cannabis is a lot safer than other drugs patients turn to in times of distress, mental healthcare professionals would be wise not to discredit the herb outright.

On the other hand, the therapists themselves have a tough role. It’s entirely possible, for example, that THC use is causing someone to experience acute anxiety, or that their chronic weed use is keeping them from fulfilling their day to day responsibilities. Again, it’s all about communication.



It is worth mentioning that psychedelic psychotherapies are becoming accepted by the scientific community. Herbs and substances like ketamine, MDMA, ayahuasca, and magic mushrooms are being tested as therapeutic agents against mild or severe mental conditions. Cannabinoids are not psychedelics in a strict sense, yet in countries where cannabis is legal, assisted psychotherapy sessions under the effects of cannabinoids are now offered. For instance, some US states offer cannabis-assisted psychotherapy for around $350, after which a driver is required by law to return you home.

When it comes to mental illnesses, each and every condition requires unique care and treatment. That means that cannabinoids may affect different conditions in distinct ways. Let’s look into some of the research on the developing role of cannabis in mental healthcare.


It’s well-known that THC can make people feel more relaxed, less stressed, and in a better overall mood. Unfortunately, THC can also induce some side effects, particularly in inexperienced or sensitive users. THC is known to trigger anxiety and paranoia at high doses. Intriguingly, CBD is effective at reducing some of these negative psychotropic effects by lowering THC’s ability to bind with CB1 cannabinoid receptors.

While CBD is gaining more and more traction when it comes to future treatments for psychological disorders, THC displays efficacy in its own right—especially regarding bipolar disorders. These conditions involve periods of maniacal high energy, alternating with periods of extremely low mood and depressive episodes. Cannabis use is actually higher in bipolar patients, probably because they use it to alleviate depression and come down from manic episodes as well. The typical biphasic effect of cannabinoids—where different doses produce different effects (ie. sedative vs. uplifting effects)—seems to work well for some patients with this condition.

Nevertheless, and despite promising anecdotes, studies on patients with bipolar disorder or schizophrenia[1] using cannabis have yielded some pretty inconclusive findings, both in gauging the medical efficacy of THC, and its specific use cases. Studies did observe cannabis use was associated with better neurocognitive function in subjects with bipolar disorder, but the opposite was found in the schizophrenic subjects.



CB1 receptors are widespread throughout the brain, and recent neuroimaging techniques have shown increased CB1 receptors in multiple brain regions linked to post-traumatic stress disorder. Cannabinoids affect the hippocampus, an area of our brain that plays a role in learning and memory. This area is important for anxiety disorders like PTSD because it contributes to the mechanisms of danger and safety.

The role of cannabinoids in learning processes related to danger and safety makes them of interest to anxiety and PTSD researchers. The endocannabinoid system (ECS) appears to be involved in the extinction of aversive memories. Both THC and CBD are able to modulate the ECS, albeit in very different ways, and scientists want to discover if these actions have any implications for these psychological conditions. 

Millions of patients with anxiety disorders report that cannabis provides relaxation, serenity, and a calming effect. PTSD patients specifically report that cannabis helps them with insomnia, anxiety, and mood swings. Still, even here the reports on THC efficacy are varied. Some research says cannabis use alone does not appear to lead to long-term recovery from anxiety disorders or PTSD, yet other studies suggest that cannabis might play some role in a proper treatment. In short, little is known about the effect of cannabis on the natural recovery from anxiety disorders and PTSD.


When the words “cannabis” and “schizophrenia” appear in the same sentence, the topic usually revolves around mental health issues caused by the plant. While a link exists between THC (the psychotropic cannabinoid) and the cognitive condition (frequent use at a young age doubles the risk[2] of schizophrenia development in the future), researchers are looking at other cannabinoids to try and tackle it.

A multicentre randomised controlled trial[3] published in The American Journal of Psychiatry administered 1000mg of CBD daily to patients with schizophrenia, alongside their existing psychotic medication. The study took place over six weeks, and the changes in the experimental group were compared to those who received a placebo.

The researchers claim that the mechanism of CBD in this context doesn’t depend on dopamine D2 receptors (the gene codes for this site are linked to mental health conditions[4]), and likely stem from interactions with ECS enzymes, TRPV1 and serotonin receptor interaction, and partial interaction with the D2(high) receptor.

However, more human trials are needed to uncover if CBD is of any use for schizophrenia, and a systematic review[5] that analysed the data regarding cannabis and the condition concluded that “there is insufficient evidence for an effect of THC or CBD on symptoms, cognition, and neuroimaging measures of brain function in schizophrenia”.



Patients who use cannabis with decent amounts of THC are happy with its lack of side effects compared to common prescription drugs. However, there are some cases where THC has the potential to decrease the effectiveness of other drugs, or even cause unpredictable reactions and worsen the condition. Cannabis has shown to help people who suffer from depression, but using it while on antidepressants can be dangerous as cannabinoids can intensify the side effects. This can also happen with sedatives, alcohol, or other drugs, as patients may feel overly sedated when consuming THC together with a tranquiliser.

Cannabidiol can also prevent the proper metabolism of many pharmaceutical drugs. CBD is metabolised by cytochrome P450 enzymes; it then essentially deactivates these enzymes, preventing them from effectively metabolising other drugs. This is crucial to understand for those individuals taking certain medications—like some antipsychotics—as it can result in more pronounced side effects.


The peculiar interactions between cannabinoids and our mind are far from being understood. The lack of comprehensive, large-scale studies makes it exceedingly difficult to draw conclusions on a psychological or psychiatric perspective. Cannabinoids might help with some mental conditions, but they also might increase some symptoms or worsen a therapy. Furthermore, we are far away from knowing the optimal doses and standard methods of cannabis administration for psychiatric use.

Despite our present lack of knowledge, cannabinoids are seen as greatly promising since they target different neurotransmitter systems than traditional drugs, with the potential of being more effective and less disruptive.

External Resources:
  1. Opposite Relationships Between Cannabis Use and Neurocognitive Functioning in Bipolar Disorder and Schizophrenia - PubMed
  2. The Association Between Cannabis Use and Schizophrenia: Causative or Curative? A Systematic Review
  3. Psychiatry Online
  4. D2 dopamine receptor gene in psychiatric and neurologic disorders and its phenotypes
  5. The Impact of THC and CBD in Schizophrenia: A Systematic Review
This content is for educational purposes only. The information provided is derived from research gathered from external sources.

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