The role of cannabis within psychiatry is complicated and controversial. On the one hand, an increasing body of anecdotal and scientific evidence suggests that smoking pot helps alleviate the symptoms of numerous psychiatric disorders. At the same time, though, some studies suggest that there may be an association between cannabis use and an increased risk of mental health problems.
The relationship between cannabis and bipolar disorder is therefore not entirely clear, and without major clinical trials it’s difficult to say whether weed attenuates or exacerbates the condition.
Can You Use Cannabis If You Have Bipolar Disorder?
Bipolar is an affective disorder that is characterized by manic and depressive episodes. To date, most studies have focused on the interaction between bipolar disorder and cannabis use disorder (CUD). In other words, scientists have only looked at patients with co-morbid conditions and haven’t really investigated the effects of moderate cannabis use in people with bipolar depression. Nor have there been any major studies on the risk of developing bipolar disorder among healthy cannabis users.
One longitudinal study found that bipolar patients who also have CUD tended to develop the disorder at an earlier age. In patients who habitually used weed, the first manic episodes occurred 5.6 years earlier than in those without any substance use disorders. The first depressive episode, meanwhile, occurred almost six years earlier in bipolar patients with CUD than in those without a marijuana problem[i].
Another systematic review found that compulsive cannabis use resulted in higher rates of bipolar-related symptoms in those who had been diagnosed with the disorder. “The bipolar-related symptoms assessed in this study included manic, hypomanic, and depressive episodes, indicating an overall worse course of illness in individuals with comorbid BD and CUD,” write the authors of the meta-analysis[ii].
At the same time, several studies have found that bipolar patients who also suffer from CUD have an increased risk of suicide attempts than those who don’t use cannabis problematically[iii].
On the other hand, some research suggests that individuals with bipolar disorder who self-medicate with cannabis may have better cognitive function than those who don’t use weed. Domains such as working memory, attention, executive function, psychomotor speed and verbal learning have all been demonstrably boosted in cannabis users with bipolar, though more studies are needed to verify this.
Interestingly, one study indicated that cannabis helps bipolar sufferers engage in less risky decision-making and work more efficiently. Though the researchers haven’t yet looked into the neural correlates of this effect, they suspect that cannabis may help to restore dopamine deficits in people with bipolar disorder[iv].
Yet another study revealed that cannabis reduced anger, tension and depressive symptoms in those with bipolar. Smoking weed also resulted in higher levels of vigor in as little as four hours. Interestingly, the study found that cannabis only produced these effects in bipolar sufferers and not in healthy controls.
Overall, the picture is pretty murky, and cannabis use seems to be associated with both improvement and impairment in bipolar sufferers.
Is Cannabis Use A Risk Factor For Bipolar Disorder?
Studies have consistently shown that cannabis use disorder is considerably more common in people with bipolar disorder than in the general population. Bipolar patients are also far more likely to develop problematic marijuana use than those with schizophrenia, major depressive disorder, psychosis, or other mental illness.
In one study, individuals with bipolar were almost seven times more likely than non-sufferers to report cannabis use at some point in their lives and 29.4 per cent more likely to meet the DSM-IV criteria for cannabis use disorder[v]. In another analysis involving more than 50,000 participants, almost a quarter of those with bipolar also had CUD. By comparison, the prevalence of cannabis use disorders among the general population is roughly two to seven per cent.
At first glance, figures like this make it seem like activating your cannabinoid receptors automatically increases your chances of developing bipolar disorder, although the reality is less straightforward. For instance, an important genetic analysis revealed that those carrying certain genes associated with bipolar depression were significantly more likely to use cannabis. Yet, those with a “genetic liability to lifetime cannabis use showed no association with the risk of bipolar disorder.”[vi]
In other words, people who are genetically susceptible to bipolar depression are more likely than the general population to abuse cannabis, but using cannabis does not increase a person’s chances of developing bipolar. “No evidence was found for a causal effect of liability to cannabis use on the risk of bipolar disorder,” explain the study authors.
The Final Verdict
Like all mood disorders, bipolar depression is a complex condition that involves a multitude of neurotransmitter systems and is not fully understood. As with major depression and other similar illnesses, the endocannabinoid system is likely to play a role in the pathology of bipolar, which means ingesting cannabinoids like delta-9-tetrahydrocannabinol (THC) or cannabidiol (CBD) may have an impact on symptom severity.
However, until the neuroscience behind bipolar disorder is better understood, it’s difficult to say whether using weed will produce positive or negative outcomes for those with the condition. Based on the available scientific evidence, it seems that the effects of cannabis use can go both ways and vary from person to person.
At present, bipolar is not listed as a qualifying condition for medical marijuana in any country or state. However, as anecdotal reports about the positive effects of cannabis spread, more people now seem to be using weed to treat their manic symptoms, alleviate depression and enhance their overall mental health.
It’s worth remembering, though, that none of these claims have been sufficiently verified. Anyone who has a family history of bipolar disorder or other risk factors should therefore speak to a qualified healthcare practitioner before experimenting with cannabis.
[i] Leite RT, Nogueira SD, Nascimento JP, Lima LS, Nóbrega TB, Virgínio MD, Moreno LM, Sampaio BH. The use of cannabis as a predictor of early onset of bipolar disorder and suicide attempts. Neural plasticity. 2015 May 13;2015. - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4444580/
[ii] Lucatch AM, Coles AS, Hill KP, George TP. Cannabis and mood disorders. Current Addiction Reports. 2018 Sep;5:336-45. - https://pubmed.ncbi.nlm.nih.gov/30643708/#:~:text=Recent%20findings%3A%20Patients%20with%20mood,compared%20to%20the%20general%20population.
[iv] Pinto JV, Medeiros LS, da Rosa GS, de Oliveira CE, de Souza Crippa JA, Passos IC, Kauer-Sant’Anna M. The prevalence and clinical correlates of cannabis use and cannabis use disorder among patients with bipolar disorder: A systematic review with meta-analysis and meta-regression. Neuroscience & Biobehavioral Reviews. 2019 Jun 1;101:78-84. - https://www.sciencedirect.com/science/article/abs/pii/S0149763419300132?via%3Dihub
[v] Agrawal A, Nurnberger Jr JI, Lynskey MT, Study TB. Cannabis involvement in individuals with bipolar disorder. Psychiatry research. 2011 Feb 28;185(3):459-61. - https://www.sciencedirect.com/science/article/abs/pii/S0165178110003811
[vi] Jefsen OH, Speed M, Speed D, Østergaard SD. Bipolar disorder and cannabis use: A bidirectional two‐sample Mendelian randomization study. Addiction Biology. 2021 Nov;26(6):e13030. - https://onlinelibrary.wiley.com/doi/10.1111/adb.13030