Cannabis 'addictive and causes mental health problems', 20 year study finds

One in 10 users become addicted, according to the study by the World Health Organisation, and withdrawal is 'harder than heroin' it has been claimed

Cannabis is 'addictive and can cause mental health problems', a 20-year study of the drug found.

Smoking dope is now as common as smoking tobacco among teens and young adults with its use having "grown tremendously" in the past 20 years.

However it is impossible to fatally overdose from it, the study confirmed.

World Health Organisation expert advisor on addiction Wayne Hall reviewed cannabis research since 1993 and set out the effects of cannabis use on mental and physical health.

Professor Hall, a professor of addiction policy at King’s College London, told the Mail Online: "If cannabis is not addictive then neither is heroin or alcohol.

"It is often harder to get people who are dependent on cannabis through withdrawal than for heroin – we just don’t know how to do it." 

The findings found that the adverse effects of heavy cannabis use is the risk of developing a 'dependence syndrome'.

Around one in 10 of all cannabis users and one in six among those who start in adolescence do become addicted.

Mark Winstanley, of the charity Rethink Mental Illness, told the Mail: "Too often cannabis is wrongly seen as a safe drug, but as this review shows, there is a clear link with psychosis and schizophrenia, especially for teenagers.

"The common view that smoking cannabis is nothing to get worked up about needs to be challenged more effectively."

Regular cannabis users double their risks of experiencing psychotic symptoms and disorders, especially if they have a personal or family history of psychiatric episodes, and if they start using cannabis in their mid-teens.

Other findings in the study included:

• Teenagers who smoke dope regularly are at double the risk of being diagnosed with schizophrenia or reporting psychotic symptoms in adulthood.
• Teenage cannabis smokers do worse at school achieving poorer exam result.
• The study suggests teenagers will smoke into the adulthood impairing intellect, but the mechanism and reversibility of the impairment is unclear.
• Regular cannabis smokers have a higher risk of developing chronic bronchitis and if they continue into middle age probably increases the risk of myocardial infarction, a heart problem.
• Driving while cannabis-intoxicated doubles the risk of a car crash which increases if combined with alcohol.
• Smoking whilst pregnant harms your baby by stunting its growth.

The report is published online today in the scientific journal Addiction.

http://www.mirror.co.uk/news/uk-news/cannabis-addictive-causes-mental-health-4393439 07/10/2014