Mental Health and Marijuana

This information was prepared by the National Cannabis Prevention and Information Centre in Australia, and used with permission.  Some information may not be accurate for U.S. readers.

The link between the use of marijuana and mental health problems is an issue that receives a great deal of attention in the research and general media. Although severe illnesses such as schizophrenia have received a large portion of this attention, there is also debate about whether the use of marijuana can lead to more common psychiatric disorders such as depression and anxiety.

There have been a number of studies that have explored the link between marijuana use and mental health symptoms. Strong associations are often found but this is not the same as a causal link (i.e. one causes the other).

Does smoking marijuana cause schizophrenia?

Psychosis refers to a number of mental illnesses where people experience difficulty in telling what is real and what is not. Someone suffering from a psychosis might hear voices that are not really there (hallucinations), or believe things that are not true (delusions). Schizophrenia is a form of psychosis.

Hallucinations and delusions can also be accompanied by muddled thinking and speech, making it difficult for other people to understand the person.

There have been reports of people experiencing these psychotic symptoms after smoking a lot of marijuana or more marijuana than they are used to. This is rare and the symptoms, although frightening at the time, usually go away if use of marijuana is stopped. marijuana has been shown to make psychotic symptoms worse in those who already have a psychotic disorder such as schizophrenia.

Some claim that marijuana can cause schizophrenia. Evidence suggests that marijuana may somehow trigger schizophrenia in those who are already at risk of developing the disorder. Those with a vulnerability to develop schizophrenia, such as having a family history of the illness, should be strongly advised against using marijuana for this reason.

Does smoking marijuana cause depression or anxiety?

The link between marijuana and other more common mental health disorders such as depression and anxiety is confusing, because often marijuana is used to relieve symptoms of depression and anxiety.

Marijuana may seem to help ease depression before the effects of the drug wear off; however after that, smoking marijuana may make depression worse. Those who use marijuana have been shown to have higher levels of depression and depressive symptoms than those who do not use marijuana. Although results are mixed, there is a substantial amount of evidence to suggest that marijuana use, particularly frequent or heavy use, predicts depression later in life. Young women appear to be more likely to experience this effect.

Marijuana can lead to symptoms of anxiety, such as panic, in the short-term, but there is a lack of evidence pointing to marijuana as an important risk factor for chronic anxiety disorders.

Are some people more at risk than others?

Generally speaking, those who start smoking marijuana earlier (early adolescence) and smoke heavily are more likely to experience negative consequences. This may in turn lead to mental health problems, but also lead to more general life problems, like conflict at home or school / work, financial problems and memory problems.

Again, if someone has a genetic vulnerability or has an existing mental health issues, marijuana should be avoided.

What help is available?

Drug and alcohol services and mental health services are available in most areas and ideally, a coordinated approach that will tackle both issues at the sample time can be arranged. Often medication is available to assist with symptoms and this can be managed by a skilled general practitioner. Additionally there are some psychologists and social workers who may have specific training in this area.

Factsheet information taken with permission from the NCPIC web site.
Coming soon: updates to this page with U.S. data and information.