As cannabis has become legal for medical and recreational purposes in many states, discussing risks and benefits of cannabis in relationship to health and illness has become part of routine medical care. Physicians are fielding questions about marijuana prescriptions for many different illnesses. Products containing the cannabidiol (CBD) component of cannabis, have exploded onto commercial platforms as over-the-counter products with claims of health benefits for every type of symptom. Our job as physicians is to try to present treatment options and balance the risks and benefits. Unfortunately, for now, too little information is available about the effectiveness of “medical” marijuana for me to offer an opinion informed by any scientific evidence in these areas.
In psychiatry, we have historically been more focused on the negative effects of cannabis use on psychiatric conditions. The correlation between cannabis use disorder (heavy use) and higher rates of depression is well established. Similarly, many studies show an association between cannabis use and onset of psychosis, and the higher the level of cannabis use, the higher the risk of psychosis occurring. These relationships have been well studied and found in many replicated studies. Although these studies have yet to confirm any causation in these relationships, but the correlations are robust.
The story is similar for bipolar disorder. The scientific research so far shows that cannabis use increases the risk of manic episodes, and that it may be related to earlier onset of first manic episodes. At least one study showed that people who quit using cannabis after a first manic episode did much better in terms of their recovery than people who kept using cannabis. Those who still used had more frequent recurrence of mood episodes and more difficulty with functioning.
In My Practice . . .
In my practice, over the last two years, I have had several young people present to me with new onset of manic and psychotic symptoms, and they were all heavy users of cannabis. Three were women, and one was a young man. They were all in their early to mid-twenties. Three out of four were heavy recreational users and had been for a long time. One was not a recreational user, but had been prescribed medical cannabis, with high THC content, through a local clinic, for back pain. They all had suffered with depression from earlier in life — childhood/early adolescence — but none had experienced mania or psychosis before. At least one had a family history of bipolar disorder.
All of these young people had good response to medications, including mood stabilizers and antipsychotics. However, those who continued to use cannabis still had a much harder time getting back into their school or work life. Those who were still using had a harder time staying on their psychiatric medications and with maintaining their sleep and wake cycles. They became more depressed and still had breakthrough delusional symptoms at times, which did not occur with the patients who stopped smoking marijuana.
I can’t say with any clarity how the cannabis use related to their manic episodes in my patients. It was definitely notable to me that this was a pattern that I was seeing and that their patterns of recovery were at least somewhat related to their continued use or their abstinence from cannabis. These four young people experienced patterns of bipolar symptoms and cannabis use that have been well described in the scientific studies about this combination.
Does Cannabis Help Any Psychiatric Conditions?
The flip side of this discussion is whether any evidence suggests that cannabis could be used to treat any psychiatric conditions. And this is where our research becomes much scarcer. From basic research, we do know that our brains have cannabinoid receptors. A brain system referred to as the “endocannabinoid system” is at the center of many complex interactions that regulate mood, thought, and behavior. The endocannabinoid system also has interactions with our immune system and inflammatory responses.
Because these cannabinoid receptors are so important to mood and other brain functions, there is hope that somehow cannabinoid compounds can be harnessed to treat some psychiatric symptoms. However, research about how this would actually work is limited. Many factors are at play in how these receptors and chemicals affect each other, and these factors make this whole body of research rather daunting. One of these factors is genetics; people’s genes affect how they respond to different cannabinoid chemicals. Another factor is a strong placebo response to cannabinoids, and the social/cultural expectations related to the use of these compounds.
Cannabis itself includes a number of different cannabinoid chemicals. The two that most people know about are tetrahydrocannabinol (THC), and cannabidiol (CBD). THC causes the psychoactive effects of cannabis; it causes the “high.” CBD affects the brain and body, but it does not cause a change in mental status; you don’t feel different in how you are thinking and experiencing the world. CBD has a range of reported effects — including reducing inflammation and, for some people, reducing anxiety. In states where you can buy recreational or prescription cannabis, you can usually purchase well defined “blends” of the two compounds. Research in this area typically focuses on cannabis, which includes at least some THC, or CBD only, which does not include any THC.
Research on medical uses of cannabis for brain illnesses shows that it can reduce pain and spasticity in conditions such as amyotrophic lateral sclerosis (ALS) and multiple sclerosis (MS). It may also reduce pain and rigidity in people with Parkinson’s disease. It has some benefits for some children with severe epilepsy that isn’t responding to typical seizure medications. However, research on cannabis in schizophrenia and bipolar disorder have not shown evidence of medical benefits of cannabis for these disorders. Heavy cannabis use is associated with worsened outcomes in bipolar disorder and it is associated with higher risks of onset of psychosis and schizophrenia. While any causal relationship remains unknown, no studies show that use of cannabis is associated with reduced symptoms. Similarly, depression rates are higher in groups of people who are heavy users of cannabis, and no solid evidence supports its use in the treatment of depression.
CBD for Certain Psychiatric Disorders
The use of CBD in psychiatric disorders may be more promising. Interestingly, some evidence shows that CBD could possibly be used to reduce some symptoms of schizophrenia. A well-done study from last year involved giving patients with schizophrenia CBD in addition to their regular medications and giving a control group a placebo instead. At the six-week mark, the patients taking the CBD had fewer psychotic symptoms compared to the placebo group. Given the challenges of treating schizophrenia, this could prove to be important in helping patients with recovery. (McGuire, P., Robson, P., Cubala, W. J., Vasile, D., Morrison, P. D., Barron, R., … Wright, S. (2018). Cannabidiol (CBD) as an adjunctive therapy in schizophrenia: A multicenter randomized controlled trial. American Journal of Psychiatry, 175(3), 225–231. )
Some research also suggests that CBD may reduce symptoms of some anxiety disorders, in particular, social anxiety disorder. CBD may also have a role in helping people withdraw from cannabis and tobacco. No real body of evidence identifies benefits or risks of CBD in bipolar disorder or unipolar depression.
Right now, the evidence we have strongly suggests that people with bipolar disorder should not use cannabis; it is associated with worse outcomes. In terms of CBD, no good studies show positive or negative outcomes in bipolar disorder. Any possible use of CBD would be something to discuss in detail with your doctor. Even though it doesn’t get you high, we don’t know how it might interact with mood circuits or other medications. In the future, we might find that it offers some benefits, but for now not enough information is available to make any judgments at all.