This article from The Atlantic analyzes the troubling relationship between science, propaganda, and drug policy. It highlights the recent Harvard study that claimed to have found brain "abnormalities" among marijuana users compared to controls, along with other studies involving MDMA (Thanks Morris for finding this):
A recent neuroscience study from Harvard Medical School claims to have discovered brain differences between people who smoke marijuana and people who do not. Such well-intentioned and seemingly objective science is actually a new chapter in a politicized and bigoted history of drug science in the United States.
The study in question compared magnetic resonance imaging (MRI) scans of 20 “young adult recreational marijuana users” (defined as individuals 18 to 25 who smoke at least once a week but who are not “dependent”), to 20 “non-using controls” (age-matched individuals who have smoked marijuana less than five times in their lives). The researchers reported differences in density, volume, and shape between the nucleus accumbens and amygdala regions of the two groups’ brains—areas hypothesized to affect a wide range of emotions from happiness to fear, which could influence basic decision-making.
Researchers did not make any claims about how marijuana affected actual emotions, cognition, or behavior in these groups; instead; the study merely tried to establish that the aggregated brain scans of the two groups look different. So, who cares?
Different-looking brains tell us literally nothing about who these people are, what their lives are like, why they do or do not use marijuana, or what effects marijuana has had on them. Neither can we use such brain scans to predict who these people will become, or what their lives will be like in the future.
Nonetheless the study invented two new categories of person: the “young casual marijuana user” and the young non-marijuana user. This is the latest example of turning to brain imaging to make something seem objective. Establishing brain differences among certain groups highlights the uniquely ignoble political history surrounding the criminalization of a plant.
Marijuana has a particularly frustrating existence in the U.S. There are more people in federal prisons for marijuana offenses than for violent offenses. According to the ACLU, nearly half of drug arrests in 2012 were for marijuana—close to 750,000. And almost half of those arrests were for possession alone. Almost $4 billion is spent annually on the arrest, prosecution, and incarceration of marijuana offenders. And these statistics are egregiously skewed according to race. Police in the biggest American cities like Los Angeles, Chicago, and New York arrest blacks for marijuana possession at a rate seven times greater than their arrest rate for whites, despite that marijuana use rates do not differ between blacks and whites.