Long-Term Marijuana Use Might Kill Motivation From Lower Dopamine

Researchers at the Imperial College London, UCL and King’s College London have found long-term cannabis users have lower levels of the chemical dopamine in the brain that is necessary for motivation.
Dopamine, which has several roles in the body and acts like a signal to other brain cells, was found to be lower in people who smoked marijuana regularly and who started at a younger age.

The researchers say the finding came as a surprise. Because dopamine is linked to psychosis, they expected the chemical to be higher in long-term marijuana users.

The study only looked cannabis users who experienced psychotic episodes such as strange body sensations or feeling like they were being watched or threatened by an unknown entity.