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Scientific Evidence that Marijuana Does Not Cause Aggression


One of the oldest myths about marijuana is that it will cause aggression and even violence – an idea that started around the time that marijuana came over to the United States from Mexico. Since then, we’ve been trying to ensure that this myth is discredited, as most anyone who has ever smoked cannabis will tell you that they find themselves more relaxed after a few puffs. There have been studies in the past, but one study set out to put this myth to bed once and for all. Judging from their results, they may have done just that.

A random controlled study conducted by researchers in the Netherlands gathered up 20 heavy drinkers (which was classified as 3+ drinks per day for men and 2+ drinks per day for women), 21 heavy marijuana smokers (classified as individuals who used marijuana 3+ times per week) and a control group, who do not overuse either substance. The drinking group was told to drink until their blood alcohol level reached 0.08, the common legal limit, and the marijuana users were dosed at 300 micrograms of THC per kilogram of bodyweight, which was administered through a vaporizer.

Once the two groups were appropriately intoxicated they were taken through a series of tests – the first test had them associate positive and negative words to pictures they were being shown. The second test found them playing a game in which they were told they could win cash, but their opponent could cost them to lose their money as well; they were not aware of the fact that the opponent was actually a computer designed to get them all riled up.

When they were done, they were asked to rate their feelings of aggression on a scale of 1-100 (they were also asked the same question prior to becoming intoxicated). The control group went through all the same tests but without drinking any alcohol or vaping any cannabis. For good measure – and a second control – the researchers asked the alcohol and marijuana groups to come and take the same tests again, without getting intoxicated this time.

The study found that those who got drunk were far more aggressive when they were drinking compared to the control and their own scores from when they were sober. They tried harder to win against the computer and in comparison, those who were high had less aggression towards their computer opponent. Through both that test and their own self-assessment the results seem to be consistent; alcohol makes you more aggressive and marijuana makes you less aggressive.

“The results in the present study support the hypothesis that acute alcohol intoxication increases feelings of aggression and that acute cannabis intoxication reduces feelings of aggression,” the researchers conclude.

Of course, there are always going to be people who react differently when using the same dosage as someone else when it comes to any substance – but this study shows us that in general, marijuana can lessen feelings of aggression and violence, not cause them. After decades of Reefer Madness we finally have our answer: smoking marijuana is not likely to send you into a random fit of psychotic rage – you’re much more likely to find yourself annoyed and amused at something that may otherwise cause stress and anger.