Smoking cannabis ages the brain by an average of 2.8 years – almost five times as much as excessive alcohol consumption – a major new study has revealed.
In the largest study of its kind – which is to be published in the Journal of Alzheimer’s Disease – researchers analysed over 62,000 brain scans from more than 31,000 people aged between nine months and 105 years old to determine factors that contribute to brain ageing.
Dr Daniel Amen, the study’s lead author, said: “The cannabis abuse finding was especially important, as our culture is starting to see marijuana as an innocuous substance. This study should give us pause about it.”
Scientists analysed 128 brain regions using imaging which measures blood flow to predict the chronological age of the brain.
Where there is a discrepancy between this and the person’s actual age, the researchers were then able to analyse factors contributing to accelerated brain ageing.
Dr Amen said: “Based on one of the largest brain imaging studies ever done, we can now track common disorders and behaviours that prematurely age the brain.
Alcohol abuse was found to age the brain by 0.6 years.
The Home Office recently instructed police to enforce the strict laws on cannabis, after reports emerged of forces turning a blind eye.
Earlier this year it was revealed that police in Middlesbrough are allowing cannabis users to openly flout the law.
In response, the Home Office stated: “Scientific and medical evidence is clear that recreational cannabis use can cause harm to individuals and society.”
The Government outlined its support for medical cannabis in June, but Home Secretary Sajid Javid said it was “in no way a first step to the legalisation of cannabis for recreational use”.