Regardless of whatever short-term benefit patients perceive from cannabis, the evidence points clearly to an association between usage and worsening course of bipolar disorder over time.
We frequently encounter patients who use cannabis. More than 50 indications for medical marijuana are approved by various state governments, although no indications are FDA-approved. Marijuana is legal in 36 states-and 10 states allow recreational use-but regulation of the quality or purity of these products is minimal. Some patients are convinced that marijuana calms them, uplifts them, blunts their anxiety, enables them to sleep, and has other benefits like helping with pain. Many report that it is the only thing that is reliably helpful for neuropsychiatric symptoms, compared with prescribed medications. Notably, scores of nicotine users say the same thing: it is their coping strategy of choice for just about every stress or even their “only pleasure in life.” Others say the same things about benzodiazepines. Rhetorical question: What do these substances have in common?
Regardless of whatever short-term benefit patients perceive from cannabis, the evidence points clearly to an association between usage and worsening course of bipolar disorder over time. In a study of 4915 participants, Henquet et al.1 found a strong increased risk of manic symptoms associated with cannabis over a three year follow-up (after controlling for possible covariates). They also saw an earlier age of onset of bipolar disorder, greater overall illness severity, more rapid cycling, poorer life functioning, and poorer adherence with prescribed treatments.
Zorrilla and colleagues2 evaluated the subsequent course of patients with bipolar disorder who stopped cannabis use after an illness episode and compared their outcome with patients with bipolar disorder who had never used cannabis and a group that continued to use. The total sample included 1922 patients. In a two year period, the continued users had significantly lower rates of recovery, greater work impairment, and fewer were living with a partner. The data were based on patient reports; given that fact, there was likely under-reporting and probably an underestimate of the association between cannabis use and lives worsened. A systematic review of the effects of cannabis on mood and anxiety disorders confirmed a negative association between cannabis use and long-term outcomes.3
Some patients exhibit psychotic symptoms after cannabis use. A recent study found that schizophrenia or bipolar disorder developed in many of these patients.4 This happened in 47% of patients who became psychotic on cannabis over the next four years. This was the highest incidence of conversion after initial psychosis following use of various substances: the second highest was with amphetamine, at 32%. More patients converted to schizophrenia than to bipolar. As for any possible benefits, a recent review concluded that the evidence supporting use of cannabis for psychotic (or other psychiatric) disorders is “very low” and “inadequate.”5
The non-psychiatric medical benefits of cannabis are also very thinly evidenced despite outsized claims to the contrary.6 It is said to be “irresponsible” to encourage patients addicted to opiates to switch to cannabis for their problems with pain.7
Thus, it seems that patients with bipolar disorder should stay away from cannabis in all its forms. Quitting cannabis should be on the short list of interventions if patients are not doing well. This is a tough sell in today’s political environment regarding cannabis legalization. Many newspaper editorials and politicians support its beneficial effects and use. Clinicians should not back down and accept patients’ insistence on using this product; rather, they should continue efforts to educate and to consider the problem to be a serious one that potentially interferes with otherwise appropriate and effective bipolar treatments that may be offered.
Dr Osser is Associate Professor of Psychiatry, Harvard Medical School, and Consulting Psychiatrist, US Department of Veterans Affairs, National Telemental Health Center, Bipolar Disorders Telehealth Program, Brockton, MA.
1. Henquet C, Krabbendam L, de Graaf R, et al. Cannabis use and expression of mania in the general population. J Affect Disord. 2006;95:103-110.
2. Zorrilla I, Aguado J, Jaro JM, et al. Cannabis and bipolar disorder: does quitting cannabis use during manic/mixed episodes improve clinical/functional outcomes? Acta Psychiatrica Scand. 2015;131:100-110.
3. Mammen G, Rueda S, Roerecke M, et al. Association of cannabis with long-term clinical symptoms in anxiety and mood disorders: a systematic review of prospective studies. J Clin Psychiatry. 2018;79:17r11839.
4. Starzer MSK, Nordentoft M, Hjorthoj C. Rates and predictors of conversion to schizophrenia or bipolar disorder following substance-induced psychosis. Am J Psychiatry. 2018;175:343-350.
5. Radhakrishnan R, Ranganathan M, D’Souza DC. Medical marijuana: what physicians need to know. J Clin Psychiatry. 2019;80:45-47.
6. Hill JH. Medical use of cannabis in 2019. JAMA. 2019;322:974-975.
7. Humphreys K, Saitz R. Should physicians recommend replacing opioids with cannabis? JAMA 2019; 321(7): 639-640.