Using cannabis can worsen memory, concentration and decision-making, study claims

Using cannabis can affect memory, concentration and decision-making, according to researchers.

Canadian experts reviewed the scientific evidence surrounding the drug.

They warned the effects of cannabis — or marijuana — can persist well beyond the period of intoxication.

University of Montreal scientists claimed children who smoke the drug may perform worse at school because of its effects.

And adults who use the drug, considered a class B substance in Britain, could also suffer at work or impair their driving ability.
The review, published in the journal Addiction, concluded the impairments ‘may be worse in regular and heavy users’.

More prevention measures are needed in schools to prevent adolescents using the drug chronically, researchers said.

Montreal academics analysed existing cannabis studies involving more than 43,000 people.

All of the study papers looked at how the drug affected memory, learning, attention, processing speed, language and motor function.

Researchers looked at the extent to which cannabis affects cognitive performance immediately after taking it and in the longer term.

The studies analysed ranged from experiments involving as few as 65 volunteers, to ones including thousands.

And they involved a range of smoking habits — from daily use to abstinence.

Heavy and frequent use was found to hamper decision-making, flexible thinking and self-control.

Other studies suggested regular cannabis use hampered the ability of people being to control their behaviour, and left them less able to make ‘appropriate decisions’.