What bipolar disorder is
Bipolar disorder is a serious, lifelong mental health condition characterised by recurrent episodes of mania or hypomania (elevated, expansive, or irritable mood with increased energy, reduced need for sleep, grandiosity, pressured speech, and impulsive or risky behaviour) and episodes of depression. Bipolar I disorder requires at least one full manic episode; bipolar II disorder involves hypomanic episodes and major depressive episodes. An estimated 1 to 2 per cent of the UK population has bipolar disorder.
Standard treatment in the UK, as recommended by NICE, involves mood-stabilising medication — most commonly lithium, valproate, lamotrigine, or atypical antipsychotics such as quetiapine and olanzapine — combined with psychoeducation, psychological therapy, and monitoring for relapse. Treatment is typically lifelong. Episodes can be triggered by stress, sleep disruption, and substance use.
Cannabis research on Bipolar disorder
One is an epidemiological prevalence study of psychotic and bipolar I disorders in a Finnish general population sample (Perala et al., 2007) that provides background epidemiology but no cannabis data.
The published medical literature contains a larger body of evidence, almost all of which documents risk rather than benefit.
Evidence for risk of mania
A 2015 systematic review and meta-analysis by Gibbs and colleagues, analysing six prospective studies with 2,391 participants followed for a mean of 3.9 years, found that cannabis use was significantly associated with worsening of manic symptoms in people with an existing diagnosis of bipolar disorder (systematic review and meta-analysis). In a meta-analysis of two studies that examined new-onset manic symptoms, cannabis use was associated with an approximately three-fold increase in the risk of developing new manic symptoms (odds ratio 2.97, 95% CI 1.80 to 4.90). The authors described the conclusions as preliminary given the small number and variable quality of available studies, but noted the consistency of the direction of effect.
A 2026 review of cannabis and mental health concluded that cannabis use is associated with “worsening mania symptoms and function in those with bipolar disorder” and that daily cannabis use provides “credible evidence” as a contributory cause of psychosis (human observational evidence, PMID 41801216). The review draws on epidemiological studies, longitudinal cohorts, and genetic evidence and is used for the mania-risk association as established, not speculative.
Evidence for lack of treatment efficacy
A 2026 systematic review and meta-analysis of cannabinoids for the treatment of mental disorders concluded that there were “insufficient data to meta-analyse studies of ADHD, bipolar disorder, obsessive-compulsive disorder” and several other conditions, meaning the published treatment trial literature for bipolar disorder is too thin to support any statistical summary (PMID 41856154). No randomised controlled trial of a cannabinoid preparation as a treatment for bipolar disorder has been published.
A 2025 review of cannabis and cannabinoids in mood and anxiety disorders evaluated the impact of cannabis on illness onset and course and assessed the therapeutic potential of cannabinoids for depression, bipolar disorder, anxiety disorders, and post-traumatic stress disorder (PMID 40235611). The review noted that while some preclinical research suggests cannabinoid modulation of mood circuits, the clinical evidence for therapeutic use in bipolar disorder is absent and outweighed by evidence of harm.
Specific risks in bipolar disorder
A 2025 case report documented a manic episode induced by cannabidiol (CBD) in a patient with no prior psychiatric history (PMID 40630971). CBD is non-intoxicating and widely regarded as having a favourable safety profile; that it precipitated mania underscores that even non-THC cannabinoids may destabilise mood in vulnerable individuals. This is a single case report and does not establish a general risk magnitude, but it counters the assumption that CBD is categorically safe for people with bipolar disorder.
Notes on self-medication claims
A 2026 study found that people with bipolar disorder who use cannabis chronically showed decision-making and functional outcomes comparable to healthy controls, while people with bipolar disorder who did not use cannabis were impaired on these measures (PMID 41309543). The authors suggested that cannabis might attenuate some cognitive deficits in bipolar disorder. This is an observational finding from a cross-sectional design. It does not demonstrate that cannabis improves bipolar disorder outcomes, and it cannot separate cause from effect — people with milder bipolar disorder may be more likely to use cannabis rather than the reverse. The same study population would be expected to carry the mania risk documented in longitudinal research.
A 2026 study found that acute cannabis slowed temporal perception in people with bipolar disorder and suggested that cannabis use may be driven by attempts to self-medicate “racing thoughts and poor concentration” (PMID 42481733). This is consistent with the self-medication hypothesis as a description of subjective motivation, but it does not constitute evidence that cannabis use is safe or studied for bipolar disorder.
Compounds studied for Bipolar disorder
There is no evidence that any cannabinoid or terpene is a safe or effective treatment for bipolar disorder. The published evidence points in the opposite direction: cannabis use is associated with worsening of manic symptoms and increased risk of new-onset manic episodes.
THC is the cannabinoid most clearly linked to manic and psychotic symptoms in the published literature. The three-fold increased risk of new manic symptoms identified in the 2015 systematic review is primarily associated with THC-containing cannabis. THC’s psychoactive effects include stimulation, euphoria, reduced sleep, and racing thoughts — effects that overlap with or could trigger manic symptoms in susceptible individuals.
CBD has not been studied as a treatment for bipolar disorder in any clinical trial. A 2025 case report documented a manic episode following CBD use, suggesting that even non-intoxicating cannabinoids are not risk-free in this population. The preclinical evidence for CBD’s antipsychotic and mood-stabilising properties in animal models does not override the absence of human treatment data and the existence of a documented adverse event.
CBG has no published evidence in bipolar disorder.
Limonene has shown anxiolytic and mood-elevating effects in preclinical research involving healthy volunteers, but has never been studied in a bipolar disorder population. The subjective appeal of mood elevation is not a treatment rationale for a condition where elevated mood is itself a core symptom of the manic phase.
Linalool has anxiolytic and sedative properties in animal models. No human research has tested linalool for any bipolar disorder outcome.
Limits of the evidence for Bipolar disorder
The most important evidence limit is that what evidence exists for cannabis and bipolar disorder points to risk, not benefit. A systematic review and meta-analysis found a three-fold increase in the risk of new manic symptoms associated with cannabis use. Multiple reviews have concluded that cannabis worsens manic symptoms and functioning in people with bipolar disorder.
No randomised controlled trial of any cannabinoid preparation as a treatment for bipolar disorder has been published. There is no dose, no safety protocol, no efficacy data, and no monitoring framework for cannabinoid use in this population.
The self-medication hypothesis — that some people with bipolar disorder use cannabis because they subjectively feel it helps with racing thoughts or low mood — is a description of motivation, not a treatment recommendation. The subjective appeal of cannabis does not mitigate the documented risk of destabilising the disorder.
The 2025 CBD-induced mania case report indicates that even cannabinoids perceived as low-risk can have serious adverse effects. People with bipolar disorder, and their clinicians, should not assume that CBD or non-THC products are safe simply because they are non-intoxicating.
Related conditions
- Depression ; limited, mixed evidence
- Anxiety disorders ; CBD laboratory studies and THC dose effects
- Schizophrenia risk ; evidence on cannabis use, risk, and clinical guidance
- Addiction and substance use ; cannabis and comorbid substance use
Read next
- THC ; the cannabinoid most associated with mood-altering effects
- CBD ; examined for mood-stabilising properties in preclinical models
- Browse the cannabinoid reference
- Browse the terpene reference
Sources
1. Gibbs M, Winsper C, Marwaha S, Gilbert E, Broome M, Singh SP. Cannabis use and mania symptoms: a systematic review and meta-analysis. Journal of Affective Disorders. 2015;171:39-47. PMID: 25285897. Study record
2. Cannabis and Mental Health: A Review. 2026. PMID: 41801216. Study record
3. The efficacy and safety of cannabinoids for the treatment of mental disorders and substance use disorders: a systematic review and meta-analysis. 2026. PMID: 41856154. Study record
4. Cannabis and Cannabinoids in Mood and Anxiety Disorders: Impact on Illness Onset and Course, and Assessment of Therapeutic Potential. 2025. PMID: 40235611. Study record
5. Cannabidiol Induced Manic Episode: A Case Report. 2025. PMID: 40630971. Study record
6. Chronic cannabis use in people with bipolar disorder is associated with comparable decision-making and functional outcome to healthy participants. 2025. PMID: 41309543. Study record
7. Evidence for pro-cognitive benefits of cannabinoids in people with bipolar disorder. 2026. PMID: 42481733. Study record
