Part of the show Forensic anthropology, and Facial Reconstruction - Naked Scientists
Cannabis users face long-term irreversible damage to their memories, says recent research published in America. The bad news is that you don't need to take much to produce the effects. In the study, people who used Cannabis as little as once per week for only 3 years showed a decline in their memory, and the longer they took it for, the worse their memory became. The subjects in the study were asked to recall words a certain time after they had been shown them. The cannabis users remembered an average of 2.5 fewer words than non-users (JAMA 2002;287: 1123-31) But is the damage permanent ? Unfortunately it looks like it because the subjects continued to show these effects on their memories even after they had stopped using Cannabis. So the best advice can only be to avoid Cannabis since it seems to produce permanent brain damage which gets worse the more times you take it.