Marijuana and psychosis

Does long term use of marijuana lead to mental illness? There have been concerns raised about a possible link between marijuana and psychotic illnesses such as schizophrenia.

It is argued that people who are psychologically vulnerable or have a family history of diseases such as schizophrenia are more likely to develop this as a result of using marijuana.

The main argument centres on psychosis and whether there is an association between this and marijuana use.

What is psychosis?


This is a psychiatric term for a condition in which someone appears to have lost all connection with reality. They are displaying an abnormal state of mind and exhibit the following symptoms:

  • Hallucinations
  • Personality disorder
  • Paranoid delusions
  • Abnormal or ‘weird’ behaviour

Someone who displays any of these is considered to be psychotic.

There are various causes of psychosis which include drug abuse, brain tumour, brain injury, severe stress and manic depression (bipolar disorder).

Someone who has an ‘addictive personality’ or a genetic predisposition to mental illness is more likely to have a negative experience with marijuana.

They may have unpleasant hallucinations, become anxious or suffer a panic attack as a result. Heavy doses of marijuana will cause this as will strong versions such as skunk or sinsemilla.

It appears to be the case that marijuana worsens existing mental health conditions such as schizophrenia. So if you have already been diagnosed with this then marijuana may exaggerate the symptoms.

But, there is little evidence to show that marijuana causes schizophrenia or is likely do so in people who have used it over a long period of time (or are heavy users).

(Source: DrugScope: Re: the Advisory Council on the Misuse of Drugs: Jan 2006).

More research is needed to determine if there is a link between marijuana and psychosis.

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