New study suggests minimal relationship between cannabis and schizophrenia or psychosis

October 22, 2009,

Last year the UK government reclassified cannabis from a class C to a class B drug, partly out of concerns that cannabis, especially the more potent varieties, may increase the risk of schizophrenia in young people. But the evidence for the relationship between cannabis and schizophrenia or psychosis remains controversial. A new study has determined that it may be necessary to stop thousands of cannabis users in order to prevent a single case of schizophrenia.

Scientists from Bristol, Cambridge and the London School of Hygiene and Tropical Medicine took the latest information on numbers of cannabis users, the risk of developing , and the risk that cannabis use causes schizophrenia to estimate how many cannabis users may need to be stopped to prevent one case of schizophrenia.

The study found it would be necessary to stop 2800 heavy cannabis users in young men and over 5000 heavy cannabis users in young women to prevent a single case of schizophrenia. Among light cannabis users, those numbers rise to over 10,000 young men and nearly 30,000 young women to prevent one case of schizophrenia.

That's just part of the story. Interventions to prevent cannabis use typically do not succeed for every person who is treated. Depending on how effective an intervention is at preventing cannabis use, it would be necessary to treat even higher numbers of users to achieve the thousands of successful results necessary to prevent a very few cases of schizophrenia.

Matt Hickman, one of the authors of the report published last week in the scholarly journal Addiction, said that "preventing cannabis use is important for many reasons - including reducing tobacco and drug dependence and improving school performance. But our evidence suggests that focusing on schizophrenia may have been misguided. Our research cannot resolve the question whether cannabis causes schizophrenia, but does show that many people need to give up cannabis in order to have an impact on the number of people with schizophrenia. The likely impact of re-classifying in the UK on schizophrenia or incidence is very uncertain."

Source: Wiley (news : web)

Related Stories

Recommended for you

Can psychedelic drugs 'reconnect' depressed patients with their emotions?

January 15, 2018
Imperial research suggests psilocybin can help relieve the symptoms of depression, without the 'dulling' of emotions linked with antidepressants.

Study listens in on speech development in early childhood

January 15, 2018
If you've ever listened in on two toddlers at play, you might have wondered how much of their babbling might get lost in translation. A new study from the University of Toronto provides surprising insights into how much children ...

Study suggests people dislike you more for humblebragging than for regular boasting

January 12, 2018
A team of researchers from Harvard University and UNC-Chapel Hill has conducted a study regarding humblebragging—in which a person boasts about an achievement but tries to make it sound less boastful by minimizing it—and ...

Can writing your 'to-do's' help you to doze? Study suggests jotting down tasks can speed the trip to dreamland

January 11, 2018
Writing a "to-do" list at bedtime may aid in falling asleep, according to a Baylor University study. Research compared sleep patterns of participants who took five minutes to write down upcoming duties versus participants ...

Study identifies brain circuit controlling social behavior

January 11, 2018
A new study by researchers at Roche in Basel, Switzerland has identified a key brain region of the neural circuit that controls social behavior. Increasing the activity of this region, called the habenula, led to social problems ...

Tamper-resistant oxycodone tablets have no impact on overall opioid use

January 11, 2018
The introduction of tamper-resistant opioid tablets does not have an effect on rates of opioid use or harms at a population level, according to a new study led by the National Drug and Alcohol Research Centre (NDARC) at UNSW ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.