MailOnline 14 July 2014
Smoking cannabis does increase the risk of depression and anxiety, a new study has concluded.
U.S. researchers found the brains of users were less able to react to dopamine – the feel-good chemical that inspires a spirit of get-up-and-go.
The study adds to previous research suggesting marijuana can lead to people becoming withdrawn, lethargic and apathetic.
Psychiatrist Dr Nora Volkow, of the National Institute on Drug Abuse in the U.S., used the stimulant Ritalin to see the effect cannabis had on the brain.
Like cocaine, Ritalin raises levels of dopamine in the brain.This made it ideal for the study, published in the journal Proceedings of the National Academy of Sciences.
Of the 48 people in the study, half received the drug – while the other half acted as a control group.
Personality and brain scans showed the cannabis users had significantly blunted dopamine responses compared with the controls who had never taken the drug.