Some posts claim that people with bipolar disorder who use cannabis think more clearly. That claim comes from one small hospital study, and there is a simpler explanation for it. Most other research links cannabis use in bipolar disorder with earlier onset, worse mania and a poorer course. This part covers that evidence, what it means for depression as well, and what to do if it affects you.
Translator’s note: This forum is mainly for growers. Friends, family or customers may ask you whether cannabis “helps” with depression or bipolar disorder. This article gives you the evidence so you can answer honestly and send them to a doctor.
Read this first. This article does not recommend cannabis for depression or bipolar disorder. Do not use anything in it to change psychiatric medication. Stopping an antidepressant or a mood stabiliser suddenly is dangerous.
In Thailand, cannabis flower is a controlled herb. Only an authorised practitioner can prescribe it, on a PT 33 prescription. Take particular care if you or a close family member has had psychosis (losing touch with reality), bipolar disorder or serious depression. See Contraindications and Cautions.
If you are struggling with your mood right now, talk to a doctor or someone you trust. Do not act on something you read on a forum. In Thailand, call the Department of Mental Health hotline 1323 (24 hours). Elsewhere in Southeast Asia, call your local emergency number.
This is Part 2. Part 1: Cannabis, Depression and Bipolar Disorder: Why the Dose-Response Curve Matters
1. The claim: bipolar patients who use cannabis think better
Bipolar I disorder is a mood illness that includes at least one episode of mania. Mania is a period of abnormally high or irritable mood, with much more energy, little need for sleep and risky decisions. Most people with bipolar I also go through periods of depression.
The claim comes from Zucker Hillside Hospital in New York, in the United States. It says that bipolar I patients who use cannabis do better than other bipolar I patients on three kinds of test:
- attention;
- processing speed, meaning how fast the brain handles information;
- working memory, meaning holding information in mind for a few seconds while you use it.
The study behind the claim was published by Braga and colleagues in 2012. It was retrospective, meaning it looked back at 200 existing patients. Fifty of them had a history of cannabis use disorder, a pattern of use the person cannot control despite harm to health, work or relationships.
The same 50 patients also had more lifetime psychosis, meaning psychotic symptoms at some point in their lives. The authors saw this as a possible sign of a poorer outlook.
Later reviews treat this puzzle as unresolved. Only a few studies exist. They do not agree on which mental skills differ between bipolar patients who use cannabis and those who do not, or whether any differ at all.
2. A simpler explanation for the claim
Before you read the result as a benefit, consider what else could produce it. One possible explanation is simple. To get and use cannabis regularly, a person has to function well enough. They have to keep contacts, manage money and leave the house.
Illness severity varies hugely among people with bipolar disorder. So “the ones who use cannabis test better” may only show who is well enough to use cannabis. It may say nothing about what cannabis does.
Researchers call the usual version of this problem “confounding by indication”. Normally the sickest patients get a treatment, so the treated group looks worse. Here it runs in reverse: the healthier patients are the ones able to use cannabis, so the users look better. A comparison that looks at patients at one point in time cannot rule this out.
What you can do: If someone sends you the “cannabis users think better” claim, ask one question. Were the users simply healthier to begin with? That one study cannot answer it.
3. What the rest of the bipolar research shows
The rest of the research on bipolar disorder mostly points the other way. Most of it comes from observational studies, where researchers watch what people already do rather than assigning a treatment.
| Finding | What the studies found |
|---|---|
| Age of onset | Cannabis use goes with mood symptoms starting at a younger age |
| Manic symptoms | Cannabis use goes with worse manic symptoms in bipolar disorder, and with manic symptoms appearing for the first time |
| Psychotic symptoms | Psychotic symptoms at some point in life are more common among cannabis users |
| Suicide attempts | More common among cannabis users |
| Course over two years | Continued use goes with lower recovery and remission rates, more relapses and more trouble working |
Sources:
- Pinto et al., 2019: a systematic review and meta-analysis of 53 studies. A meta-analysis pools the results of many studies into one estimate.
- Gibbs et al., 2015: a systematic review and meta-analysis of prospective studies, which follow people forward in time.
- Zorrilla et al., 2015: the EMBLEM study (see Section 4).
These are associations. They show which things go together, not what causes what.
4. The one finding you can act on: stopping during an episode
One result is more useful than everything in the table, because you can act on it. It comes from EMBLEM, the European Mania in Bipolar Longitudinal Evaluation of Medication. EMBLEM was an observational study in 14 European countries. It followed patients treated for a manic or mixed episode for two years. A mixed episode means symptoms of mania and depression at the same time.
Some bipolar patients stopped cannabis during a manic or mixed episode. Over the next two years, their clinical and functional outcomes were similar to those of patients who had never used cannabis. “Functional” here means daily life, such as work and relationships.
This is still an observational result. Even so, it is about the most hopeful finding in this research. It also points the opposite way from the cognition claim in Section 1.
What you can do: If you have bipolar disorder and use cannabis, tell your psychiatrist exactly what you use, how much and how often. Mention the EMBLEM result and ask whether stopping cannabis, with their support, makes sense for you. This gives the doctor the full picture and gives you a concrete, evidence-based next step.
5. Putting the evidence together
Here is the whole picture, using what Part 1 found as well.
- The mechanism is real. Cannabinoid signals affect the brain cells that make serotonin, a chemical messenger many antidepressants act on. In rats, low doses of a synthetic cannabinoid produced an antidepressant-like effect (Bambico and colleagues, McGill University, Canada, 2007).
- The curve is real too. In the same rats, the antidepressant-like effect disappeared above a certain dose, and serotonin cells fired less. This is a biphasic, or upside-down U, effect. The benefit rises to a peak and then falls, sometimes to below where it started. How you feel cannot tell you which side of the peak you are on.
- The human data point the other way. In observational studies, cannabis use goes with modestly more depression (odds ratio 1.29 in a 2025 review of 22 studies; 1.37 in a 2019 review of adolescents). Heavier use may make this worse. The cause is unresolved.
- The bipolar evidence is worse. In observational data, cannabis use goes with earlier onset, worse mania and a poorer course. Against this stands one disputed cognition finding that has an obvious alternative explanation.
- Treatment evidence is missing. No body of randomised controlled trials shows that cannabis treats either condition. In such trials, chance decides who gets the treatment.
This leaves an honest reader with no comfortable answer, and that is the correct place to be. “Cannabis helps depression” and “cannabis causes depression” are both too simple for what is known. Arguing harder will not settle the question. Only trials that nobody has run yet could do that.
What you can do: When someone asks you whether cannabis helps with depression or bipolar disorder, give a short, accurate answer. Say that no controlled trials show it treats either condition, that heavier use is linked with worse outcomes, and that they should speak to a doctor first.
6. If this is about you
Your history matters most
A personal or family history of psychosis, bipolar disorder or severe depression is the strongest caution in medical cannabis. This caution exists because THC, the main intoxicating compound in cannabis, can trigger psychotic symptoms and destabilise mood in vulnerable people. It applies whether or not the cannabis came on a prescription.
Do not stop your medication on your own
Do not stop your medication. Stopping antidepressants and mood stabilisers can cause withdrawal effects. In bipolar disorder, stopping a mood stabiliser can trigger a new episode.
Talking to your psychiatrist about cannabis is a reasonable thing to do. Changing what you take on your own is not.
Getting a psychiatric appointment in Thailand
Translator’s note: Start at the hospital or health centre where your health scheme is registered. Ask for an appointment with psychiatry or for a referral. Larger public hospitals usually have a psychiatry or mental-health clinic, and smaller ones can refer you. You can also call the 1323 hotline, which gives free mental-health counselling 24 hours a day.
What to tell the doctor about cannabis
Translator’s note: Many patients play down their cannabis use when they see a doctor. The doctor can only judge interactions and effects on mood with complete information. Before the appointment, write down:
- what you use (flower, oil, edible) and how you take it (smoked, vaporised, swallowed);
- its THC and cannabidiol (CBD) content, if you know it from the label or the certificate of analysis;
- how much, how often and for how long;
- why you started and what has changed in your mood and sleep since then;
- every medicine and supplement you take. See Cannabis Drug Interactions: The List to Take to Your Doctor.
Ask the doctor directly what they think and why. Their reasoning matters as much as their answer.
Prescriptions and products in Thailand
In Thailand, this decision belongs with a prescriber. The Notification of the Ministry of Public Health Re: Controlled Herbs (Cannabis), B.E. 2568 was issued under the Thai Traditional Medicine Protection Act B.E. 2542 and took effect on 26 June 2025. Under it, flower is sold only on a PT 33 prescription. Each prescription covers up to 30 days’ supply.
The same Notification bans advertising cannabis flower and selling it online.
Translator’s note: Flower offered for sale online is sold in breach of that ban. No prescriber has checked it against your history. If you are prescribed flower, ask for the batch’s THC content. A high-THC product makes it easier to overshoot the dose.
If you are thinking of harming yourself
Do not work this out alone or on a forum. In Thailand, call the Department of Mental Health hotline 1323 (24 hours). Elsewhere in Southeast Asia, call your local emergency number. You can also contact a doctor or someone close to you today.
If you live with depression or bipolar disorder and have discussed cannabis with a psychiatrist, please share below this topic what they said and how they explained it. Knowing how these conversations actually go in Thailand and the region is more useful than another round of general argument.
References
- Bambico FR, Katz N, Debonnel G, Gobbi G. Cannabinoids elicit antidepressant-like behavior and activate serotonergic neurons through the medial prefrontal cortex. J Neurosci. 2007;27(43):11700–11711. doi:10.1523/JNEUROSCI.1636-07.2007
- Churchill V, Sutton Chubb C, Popova L, Spears CA, Pigott T. The association between cannabis and depression: an updated systematic review and meta-analysis. Psychol Med. 2025;55:e44. doi:10.1017/S0033291724003143
- Gobbi G, Atkin T, Zytynski T, et al. Association of cannabis use in adolescence and risk of depression, anxiety, and suicidality in young adulthood: a systematic review and meta-analysis. JAMA Psychiatry. 2019;76(4):426–434. doi:10.1001/jamapsychiatry.2018.4500
- Braga RJ, Burdick KE, DeRosse P, Malhotra AK. Cognitive and clinical outcomes associated with cannabis use in patients with bipolar I disorder. Psychiatry Res. 2012;200(2–3):242–245. doi:10.1016/j.psychres.2012.05.025
- Zorrilla I, Aguado J, Haro JM, et al. Cannabis and bipolar disorder: does quitting cannabis use during manic/mixed episode improve clinical/functional outcomes? Acta Psychiatr Scand. 2015;131(2):100–110. doi:10.1111/acps.12366
- Pinto JV, Medeiros LS, Santana da Rosa G, et al. 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. Neurosci Biobehav Rev. 2019;101:78–84. doi:10.1016/j.neubiorev.2019.04.004
- Gibbs M, Winsper C, Marwaha S, Gilbert E, Broome M, Singh SP. Cannabis use and mania symptoms: a systematic review and meta-analysis. J Affect Disord. 2015;171:39–47. doi:10.1016/j.jad.2014.09.016
General educational information, not medical advice. Nothing here recommends cannabis for any psychiatric condition.