More information on cannabis and mental health

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People who use cannabis are 40% more likely to experience psychosis than people who do not use cannabis.

The more you smoke the more the risk will increase.

The younger you smoke, the greater the risk. Experts believe that this is because cannabis can affect the development of your brain.

Psychosis can happen to anyone but a family history of severe mental illness makes you more vulnerable.

About one person in 25 will experience at least one psychotic episode at some point in their life.

When you’re psychotic you lose touch with reality. This may involve terrifying hallucinations and delusions. You usually won’t realise that what’s happening to you isn’t real - no matter how much someone tries to tell you otherwise.

For those where psychosis is caused by drugs, symptoms may go away quickly. But for some, initial psychosis will develop into a long term severe mental illness such as schizophrenia.

Cannabis has loads of active ingredients, but it’s what’s known as delta-9-tetrahydrocannabinol (THC) that gets you high. It does this by binding with “receptors” in your brain. Receptors are parts of the brain that link cells so that they can “talk” to each other about our thoughts and actions. THC binds with receptors in the same part of the brain as the dopamine system. Dopamine is a chemical that sends messages about how we think, feel and behave. Psychotic symptoms are thought to be caused by too much dopamine in the brain.

Smoking cannabis can make existing psychosis worse. Its calming effects can reduce fear and anxiety in the short term, but it can cause relapse and increase the risk of developing uncontrollable muscle spasms and twitches. Because cannabis also contains mind altering chemicals it can reduce the effectiveness of antipsychotic medication.

Find out more about Rethink's cannabis and mental health campaign

For practical advice about severe mental illness call our National Advice Service on: 020 8974 6814, 10am-1pm Tuesday and Thursday, 10am-3pm Monday, Wednesday and Friday.

FRANK is a confidential drug advice line. Call 0800 776 600 or visit www.talktofrank.com.

www.csip.org.uk/mentalhealthandcannabis and knowcannabis.org.uk are good websites where you can get more info.

If you’d like a copy of our information pack about cannabis and mental health, please go to www.mentalhealthshop.org or call 08454 560 455.

• Worried about someone you know? Read Rethink's Fact Sheet Cause for Concern (49 kb)