Heavy cannabis use associated with reduced dopamine release in brain
Evidence of a compromised dopamine system has been found in heavy users of marijuana. Lower dopamine release was found in the striatum -- a region of the brain that is involved in working memory, impulsive behavior, and attention. Previous studies have shown that addiction to other drugs of abuse, such as cocaine and heroin, have similar effects on dopamine release, but such evidence for cannabis was missing until now. Ref. Source 7b.
For a long time marijuana has been put out there as some kind of wonder drug and I used to shake my head about it because I've seen people on the stuff and there was nothing wonderful about them. If anything they seemed to be slaves to marijuana.
Cannabis use can lead to various types of mental disorders, including psychotic disorders. Its consumption increases more than five times the risk of suffering from psychosis throughout life. The sooner you start using and the more frequent the use, the greater the risk.