The medical journal Jama Internal Medicine published a study on the effects of cannabis on human memory, and as expected, the results show that the drug is harmful to the human brain. Scientists ran an experiment on 3400 Americans over a 25-year period. The test subjects were given fifteen words to memorize. Dr. Filbey, Associate Professor in the School of Behavioural and Brain Sciences at the University of Texas says that:
To date, existing studies on the long-term effects of marijuana on brain structures have been largely inconclusive due to limitations in methodologies. While our study does not conclusively address whether any or all of the brain changes are a direct consequence of marijuana use, these effects do suggest that these changes are related to the age of onset and duration of use.
Half a word less for those who smoke every day
Those who smoked every day for five years remembered half a word less than those who didn't smoke, or who did, but in moderation (8.5 words versus 9). This rises to 2.5 words less after 25 years of smoking.
However, the results also show that marijuana use in no way affects your IQ or your concentration and deduction skills. Still, cannabis exposes you, among other things, to addiction and depression.
Super High Me
In a slightly less serious but nonetheless valid experiment, comedian Doug Benson tried to examine the effects of consistent cannabis use in his documentary Super High Me. Following in the footsteps of Morgan Spurlock's documentary on McDonald's called Super Size Me, Benson subbed out the burgers for bong hits. The entire documentary is available on YouTube - the official trailer can be found below.