Dumbing Down With Pot

Think using marijuana is a dumb idea? A new study suggests that heavy marijuana use can actually lower a person’s IQ score and discontinuing use of the drug may be the only way to recover lost brain power.

Heavy marijuana use smoking five or more joints a week can lower the IQ by an average of four points, according to a new Canadian study with 17- to 20-year-old subjects. According to the study, IQ levels among light marijuana users, former users, and non-users were similar, but current heavy users showed a big loss of IQ points. The effects did not seem to be permanent; people who had heavily used the drug in the past but were not current users had apparently recovered their IQ points. But the researchers warned that people who use multiple drugs or have been using marijuana for many years can’t necessarily count on regaining those brain cells.

This drop in IQ is similar to the drop shown by kids who were exposed to three alcoholic drinks a day in the womb. And it’s a greater drop than shown by kids who were prenatally exposed to cocaine or low levels of lead.

This isn’t the only study of its kind. Another study in Australia tested male marijuana users in areas like memory and judging the passage of time. Half of the test subjects had smoked heavily for over two decades, and the other half had smoked heavily for about 10 years. The results? The longer-term users had shorter attention spans and more trouble remembering things than the shorter-term users. The shorter-term marijuana users did better, but, like the longer-term users, they had trouble judging the passage of time.3

Most people who have tried marijuana know that it can leave the brain dull and “fuzzy” for a while. But these recent studies add to the mounting evidence that marijuana spells serious trouble for the brain. In addition to affecting IQ, marijuana affects receptors in the brain that control perception of depth and time, thought, memory, concentration, and coordination. When THC, a chemical in marijuana, activates these receptors, it leads to imbalance, poor posture, lack of coordination, and many of the other immediately recognizable effects of marijuana use. A person who has smoked marijuana may become clumsy, may lose track of time, and his perception of distance and speed may be impaired. Marijuana also confuses the brain, making it harder for the user to decipher between reality and the imagined.

However, the good news is that certain things, such as lost IQ, might be regained if the user quits. The safest thing is not to start using at all. If you know someone who uses marijuana, let him know that he has a “window of opportunity” to quit and heal some damage to the brain, but that researchers aren’t sure exactly how long that “window” will last. Does he really want to take a chance with the only brain he’s got?