Scientists have found no link between cannabis use and mental health problems in a study of 35,000 people
Cannabis does not increase the risk of developing anxiety or depression, a new study has found.
There has long been debate over the drug’s potential link to mental health problems.
A major study last year found that one in four new cases of psychotic conditions such as schizophrenia could be the direct result of smoking extra-strong varieties of cannabis, known as skunk.
But a study by scientists at Columbia University, based on 35,000 American adults, found no link between cannabis and anxiety and depression.
The researchers looked at the prevalence of marijuana use among participants, then assessed their rates of mental health problems three years later.
However the study did find that cannabis users are more likely to become dependent on other substances, for example being alcoholics or smokers.
Those who used cannabis had an increased risk of developing alcohol and drug use disorders, including nicotine dependence.
Users of the drug were found to be three times more likely to have alcohol problems and twice as likely to smoke cigarettes.
In the paper, published in the journal JAMA Psychiatry, the authors wrote: “Our study indicates that cannabis use is associated with increased prevalence and incidence of substance use disorders.
“These adverse psychiatric outcomes should be taken under careful consideration in clinical care and policy planning.”
The cannabis industry is becoming big business in the US, where multiple states have made the drug legal.
In the UK, many police forces quietly turn a blind eye to cannabis use.
Dr Amir Englund, a post-doctoral researcher in psychopharmacology at the Institute of Psychiatry, Psychology and Neuroscience at King’s College London, said: “The present study is a large study exploring the effects of cannabis use on future problems such as anxiety, depression and drug and alcohol addiction.
“They found that use of cannabis was related to increased risk of later addiction to alcohol, cannabis and other drugs. Cannabis was not related to anxiety or depression at follow-up.
“Of course a study such as this is unable to ascertain causality between cannabis use and later drug addiction, merely that a relationship exists.”
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