Bipolar disorder (BD) is a serious mental health condition characterized by significant shifts in mood, energy, and activity levels, fluctuating between depressive lows and manic or hypomanic highs. Bipolar I disorder involves at least one manic episode, which is a period of excessively elevated or irritable mood lasting a week or more, often requiring hospitalization for safety. Bipolar II disorder involves at least one major depressive episode and at least one hypomanic episode, a milder form of mania that does not typically cause severe impairment. A high rate of co-occurring substance use disorders exists in this population, with individuals with BD being significantly more likely to report a lifetime history of cannabis use. The medical consensus surrounding cannabis use for people with BD leans heavily toward caution and avoidance due to the risks of destabilizing mood and complicating treatment.
Immediate Risks of Cannabis Use in Bipolar Disorder
The most pressing concern regarding cannabis use in individuals with BD is the potential for acute mood destabilization, particularly the triggering of a manic episode. Introducing psychoactive substances can rapidly disrupt the delicate neurochemical balance that mood stabilizers are designed to maintain. This disruption can lead to a “switch,” where a person transitions quickly from a stable or depressive state into mania or hypomania.
Cannabis use is also strongly associated with an increased risk of psychosis or psychotic features, which is especially concerning for individuals with Bipolar I disorder. The psychoactive component of cannabis, delta-9-tetrahydrocannabinol (THC), interacts with the brain’s cannabinoid receptors. This interaction can exacerbate or trigger symptoms like hallucinations, delusions, or disorganized thinking. Experiencing a cannabis-induced psychotic episode may increase the risk of developing a chronic psychotic disorder, including BD.
Interaction with Mood and Symptom Severity
Cannabis use is linked to an acceleration of the illness’s course, including rapid cycling, where four or more mood episodes occur within a single year. This pattern of more frequent and intense episodes makes the condition significantly harder to treat and manage. Studies consistently show higher rates of hospitalization and emergency intervention among BD patients who use cannabis compared to those who do not. Continued cannabis use is associated with a lower chance of achieving long-term remission and a higher risk of recurrence of mood episodes.
Beyond the acute risks of triggering an episode, cannabis use contributes to a long-term degradation of mood stability and overall functioning in people with BD. While some individuals may initially seek cannabis for relief, the chronic use often exacerbates depressive symptoms over time. This may be due to THC’s effect on the brain’s endocannabinoid system, which helps regulate emotions and stress.
The use of cannabis is also linked to increased baseline anxiety and irritability, even when a person is not experiencing a full-blown mood episode. This general increase in emotional dysregulation makes it more difficult to maintain a stable emotional state, which is a primary goal of BD treatment.
Cannabis can also negatively affect cognitive functions, such as memory, attention, and executive function, which are already commonly impaired in BD. This compounding effect on cognition can interfere with daily life, education, and employment. Crucially, cannabis use is linked to poorer adherence to prescribed treatment plans, which is a significant factor in worsening the long-term course of the illness. Continued substance use can mask the true nature of symptoms or lead to a perception that medication is ineffective.
Impact on Bipolar Medication Efficacy
Combining cannabis with the medications used to treat BD introduces a physiological danger due to drug-drug interactions. Many common BD drugs, including mood stabilizers like lithium, valproate, and lamotrigine, and various antipsychotics, are metabolized by a family of liver enzymes known as the cytochrome P450 (CYP450) system. Cannabinoids, particularly THC and Cannabidiol (CBD), can interfere with the activity of these enzymes.
This metabolic interference alters the concentration of prescribed drugs in the bloodstream. If cannabinoids inhibit the enzymes, medication levels can build up, potentially leading to dangerously high concentrations and toxicity. For example, there is a case report of lithium toxicity occurring when combined with prescription CBD, leading to symptoms like excessive tiredness and impaired balance.
Conversely, the use of smoked cannabis can sometimes accelerate the clearance of certain drugs metabolized by the CYP1A2 enzyme, potentially lowering the drug’s concentration. This can result in sub-therapeutic levels of medication, causing a breakthrough of manic or depressive symptoms because the treatment is no longer effective. Furthermore, combining cannabis with sedating antipsychotics or other central nervous system depressants can have an additive effect, intensifying side effects such as drowsiness, confusion, and impaired coordination.
The Role of Cannabinoids (THC vs. CBD)
The cannabis plant contains hundreds of compounds, with the two most studied cannabinoids being THC and CBD. Delta-9-tetrahydrocannabinol (THC) is the primary psychoactive component responsible for the “high” and is the compound most strongly linked to the risks of psychosis and mood destabilization in BD. THC’s ability to increase dopamine levels is hypothesized to intensify manic symptoms, which are already characterized by heightened excitement and impulsivity.
CBD, or cannabidiol, is non-intoxicating and has been studied for potential anxiolytic and antipsychotic properties. Early research suggests CBD may be less problematic than THC and could hold some therapeutic promise, but current evidence is insufficient to recommend it as a treatment.
The potency of the cannabis product is also a major factor in the risk profile, with high-potency cannabis containing elevated levels of THC linked to a greater risk of adverse psychiatric outcomes. A significant concern with using non-regulated CBD products is the potential for inaccurate labeling, which can result in the unintentional consumption of THC. Even isolated CBD products carry a risk of drug-drug interaction by inhibiting the CYP450 enzyme system, which can alter the metabolism of mood stabilizers and antipsychotics. Therefore, any use of cannabis or its derivatives requires a careful risk-benefit analysis and close medical supervision.