Long-term pot use can stifle motivation
It may seem like a joke given the stereotype of the lazy stoner, but long-term marijuana use can actually have a significant impact on a person's motivation. According to research from Imperial College London, UCL and King's College, people who smoke weed regularly and those who started at a younger age have lower levels of dopamine in the part of the brain that affects motivation, called the striatum. This, said researchers, could help explain why long-term users can appear to lack motivation or do not appear interested in normal activities.
This study used PET brain imaging to observe dopamine production in the striatum of 19 pot smokers and 19 non-smokers. Before the study, the researchers suspected that dopamine levels might be higher in the smokers, as all had experienced psychotic-like effects while smoking, and dopamine can be associated with psychosis. Instead, they found just the opposite: Those who smoked pot produced less dopamine than the non-smokers. The lowest dopamine levels were seen in the smokers who met criteria for cannabis abuse or dependence, which could raise doctors' abilities to evaluate addiction severity.
The researchers also studied if this dopamine effect – and the accompanying lack of motivation – could be reversed. The results suggest that dopamine production could be restored in people who stop using the drug.