Smoking marijuana speeds up mental illness

William Atkins
Wednesday, 09 February 2011 00:08

Science - Health

Australian and American researchers found that people who smoke cannabis or other psychoactive substances have an earlier likelihood of getting psychotic illnesses, such as schizophrenia, than people who don't use such substances.

The article 'Cannabis Use and Earlier Onset of Psychosis' (doi: 10.1001/archgenpsychiatry.2011.5), published online on February 7, 2011, in the journal Archives of General Psychiatry highlights the study.

It is authored by Drs. Matthew Large, Swapnil Sharma, Michael T. Compton, Tim Slade, and Olav Nielssen.

They state in the abstract to their paper that previous studies have formed the association between cannabis use (and the use of other psychoactive substances) and the earlier presence of psychotic illnesses, such as schizophrenia.

However, the amount of time that such psychotic illnesses become apparent in those using cannabis when compared to those not taking cannabis has not been detailed.

Thus, these researchers decided to find out. Their objective: 'To establish the extent to which use of cannabis, alcohol, and other psychoactive substances affects the age at onset of psychosis by meta-analysis.' [Paper]

They used peer-reviewed, English-reporting publications that held papers on psychotic illnesses and the use/non-use of psychoactive substances. In all, they found 443 articles, and used 83 such articles in their study.

In these 83 studies, 8,167 people had a psychotic illness and used marijuana or other psychoactive substances. Another 14,352 people had a psychotic illness but did not use such substances.

Page two shows the results of the study.