Myth: Marijuana use causes permanent short-term memory loss.
The Truth: Marijuana does cause short-term memory impairment but only when you are high. Just like how alcohol impairs your balance when you are drunk but not the rest of your life. Studies show that chronic smoking of marijuana does not produce major changes in general cognitive abilities like intelligence, memory and the ability to learn. Unfortunately there are marijuana users who help perpetuate this myth.
A study in Jamaica of 30 chronic users and 24 non-users investigated cognitive effects of long-term pot use (Bowman & Pihl 1973). The users smoked an average of 20 joints per day for at least 10 years. The testing took place in many environments from homes, huts to public places. The mobile approach ensured that even the most impaired individuals could participate. The study included many tests of reaction time, learning, perception and memory. The investigators determined that chronic marijuana consumption had no effect on cognitive abilities.
A more recent study looked at mental functioning of 1300 cannabis users in Baltimore over 11 years (Lyketsos; Garrett; Liang; Anthony 1999). The study used the Mini-Mental State Examination to examine the participants. There were no significant differences in cognitive decline between heavy users, light users, and nonusers of cannabis. Read it HERE.
Other studies show that the brain adapts to the acute memory effects (while you’re high) of cannabis. A laboratory experiment on rats and mice show that short-term memory in the rats dropped initially in the 35 day examination but recovered to pre-drug levels by the end. This study also shows some interesting stuff regarding cannabinoid effect of the hippocampus. Read it HERE. The acute short-term memory effect subsides after prolonged use. Long time marijuana users will also confirm these results.
Marijuana does not make you dumb or ruin your short-term memory. The myth was created and perpetuated by the anti-drug groups which continues to this day. If this myth were true 14% of Canada and 10% of the United States would live by a system of notes, photographs, and tattoos like the guy in Memento. As mentioned in the Amotivational Syndrome Myth, college students who smoke cannabis demonstrate comparable or even higher grades than their cannabis abstinent classmates, and are more likely to pursue a graduate degree (SOURCE).
- Tolerance to the memory disruptive effects of cannabinoids involves adaptation by hippocampal neurons. Hampson, Robert E / Simeral, John D / Kelly, Erica J / Deadwyler, Sam A , Hippocampus, 13 (5), p.543-556, Jan 2003
- Bowman, M. & Pihl, R.O. 1973. Cannabis: Psychological effects of heavy use. A controlled study of intellectual functioning in chronic users of high potency cannabis. Psychopharmacologia Vol. 29(2): 159-170.
- Cannabis Use and Cognitive Decline in Persons Under 65 Years of Age, by C.G. Lyketsos; E. Garrett; K. Liang; J.C. Anthony; American Journal of Epidemiology, Vol 149 (No. 9) 1999, 794-800