Your Brain on Weed

Now that everyone has been convinced that marijuana use is harmless, it turns out that it can cause brain damage.

Who knew?

Young Americans believe that tobacco is a very harmful toxic substance. They even believe that alcohol is potentially dangerous. They know that they should avoid sugar and transfats, but they are persuaded that marijuana is just good, clean fun.

It looks like they might have been duped. I know, it’s barely conceivable, but the Journal of Neuroscience is reporting that marijuana damages the brain. The Washington Post reports:

The days when people thought only heavy Cheech-and-Chong pot smokers suffered cognitive consequences may be over. A study in The Journal of Neuroscience says even casual marijuana smokers showed significant abnormalities in two vital brain regions important in motivation and emotion.

“Some of these people only used marijuana to get high once or twice a week,” said co-author Hans Breiter, quoted in Northwestern University’s Science Newsline. Breiter hailed the study as the first to analyze the effects of light marijuana use. “People think a little recreational use shouldn’t cause a problem, if someone is doing OK with work or school,” he said. “Our data directly says this is not the case.”

“This study raises a strong challenge to the idea that casual marijuana use isn’t associated with bad consequences,” he added.

According to the study, those who smoked as little as once a week showed brain abnormalities. More smoking produced more abnormalities.

This caused problems:

In the study, scientists compared the size, shape and density of the nucleus accumbens and the amygdala, which control emotion. Those who had smoked had abnormally large nucleus accumbens, an area of the brain that controls pleasure, reward, and reinforcement learning.

In the brains of marijuana users, natural rewards are less satisfying.

“Drugs of abuse can cause more dopamine release than natural rewards like food, sex and social interaction,” said lead author Jodi Gilman. “In those you also get a burst of dopamine but not as much as in many drugs of abuse. That is why drugs take on so much salience, and everything else loses its importance.”

So, marijuana use will deprive you of the “natural” pleasures you gain from food, sex and friendship…. It might even deprive you of the satisfaction of work and achievement.

The more you smoke weed, the more everything else will lose importance. And, of course, the less you will care.

Time magazine adds that the sample was small and the results are preliminary. Besides, scientists have not yet measured how these brain abnormalities will influence behavior:

The researchers acknowledge that their sample size was small and their study preliminary. More work, they say, needs to be done to understand the relationship between the changes to the brain they found and their impact on the day-to-day lives of young people who smoke marijuana casually.

“The next important step is to investigate how structural abnormalities relate to functional outcomes,” says Jodi Gilman, an instructor at Harvard Medical School who collaborated on the study.