--- title: Recreational Marijuana Smoking Causes Abnomralities in Young Brains description: A new study from medical researchers at Harvard and Northwestern shows that 18- to 25-year-olds who smoke marijuana—even just recreationally!—had marked abnormalities in areas of their brains that regulate emotion and motivation canonical: https://time.com/61940/recreational-pot-use-harmful-to-young-peoples-brains/ author: Randye Hoder article:opinion: false article:content_tier: free article:published_time: 2014-04-15T21:00:45.000Z article:modified_time: 2026-08-04T07:45:29.136Z og:title: Recreational Marijuana Smoking Causes Abnomralities in Young Brains og:description: A new study from medical researchers at Harvard and Northwestern shows that 18- to 25-year-olds who smoke marijuana—even just recreationally!—had marked abnormalities in areas of their brains that regulate emotion and motivation og:url: https://time.com/61940/recreational-pot-use-harmful-to-young-peoples-brains/ og:site_name: TIME og:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltde093bcdab65f2d0/6988d9b9bc6cfc69913e2a3c/time-logo.jpg?branch=production og:image:width: 1200 og:image:height: 675 og:image:alt: TIME og:type: article twitter:card: summary_large_image twitter:title: Recreational Marijuana Smoking Causes Abnomralities in Young Brains twitter:description: A new study from medical researchers at Harvard and Northwestern shows that 18- to 25-year-olds who smoke marijuana—even just recreationally!—had marked abnormalities in areas of their brains that regulate emotion and motivation twitter:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltde093bcdab65f2d0/6988d9b9bc6cfc69913e2a3c/time-logo.jpg?branch=production --- # Recreational Pot Use Harmful to Young People's Brains > Sponsored content. 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Worth Your Time is TIME's culture recommendation newsletter, edited by culture editor Eliza Berman. Twice a week it surfaces the books, shows, films and ideas TIME's editors think are worth your attention, and explains why. It is free at time.com/newsletters. #### Does TIME have a culture newsletter? Yes. Worth Your Time is TIME's culture newsletter, published Tuesdays and Saturdays. #### Who writes TIME's culture recommendations? Culture editor Eliza Berman writes Worth Your Time, drawing on TIME's critics and culture desk. #### Is Worth Your Time free? Yes. It is a free newsletter available at time.com/newsletters. ## Video: That Time Has Come: Here's The First Marijuana Ad [Watch (HLS stream): That Time Has Come: Here's The First Marijuana Ad](https://cdn.jwplayer.com/manifests/50vzabYY.m3u8) (1:35)  _Published 2014-03-04. That time has come. The first marijuana commercial is due to air on major networks, including Fox, CNN, Comedy Central, and the Food Network._  by [Randye Hoder](https://time.com/author/randye-hoder/)  ## Randye Hoder Apr 15, 2014 9:00 PM UTC  by [Randye Hoder](https://time.com/author/randye-hoder/)  ## Randye Hoder Apr 15, 2014 9:00 PM UTC For those young people — and their parents — who think that smoking pot in moderation isn’t harmful, it’s time to think again. A [study](http://jn.sfn.org/press/April-16-2014-Issue/zns01614005529.pdf) released this week by researchers from Northwestern University’s Feinberg School of Medicine and Harvard Medical School has found that 18- to 25-year-olds who smoke marijuana only recreationally showed significant abnormalities in the brain. “There is this general perspective out there that using marijuana recreationally is not a problem — that it is a safe drug,” says Anne Blood, an assistant professor at Harvard Medical School and the co-senior author of the study, which is being published in [the _Journal of Neuroscience_](http://www.jneurosci.org). “We are seeing that this is not the case.” The scientists say theirs is the first study to examine the relationship between casual use of marijuana in young people and pot’s effects on two parts of the brain that regulate emotion and motivation. As such, it is sure to challenge many people’s assumptions that smoking a joint or two on the weekends is no big deal. It has certainly challenged mine. In [a piece earlier this year](http://time.com/2032/why-its-still-a-big-deal-if-your-teen-smokes-pot/), based on other research from Northwestern on the effects of heavy marijuana use, I suggested that young people should hold off on smoking pot as long as possible because their brains are still developing and the earlier the drug is taken up, the worse the effects. That remains good advice. Yet the truth is, I’ve not only been telling my own 16-year-old son to hold off, I’ve also been counseling him that should he ever decide to use pot, he should do so with temperance. This “everything in moderation” mantra has always struck me as more realistic than preaching total abstinence. Baked into my message, meanwhile, has been the implicit belief that smoking a little weed on the weekends is no worse than having a few beers — a notion that many Americans apparently share. A nationwide [NBC/_Wall Street Journal_ poll](http://www.pollingreport.com/drugs.htm) conducted last month found that only 8% of adults think that marijuana is the most harmful substance to a person’s overall health when lined up against tobacco, alcohol and sugar. In contrast, 49% of those surveyed rated tobacco as the most harmful on the list, while 24% mentioned alcohol. Notably, even sugar — at 15% — was considered more harmful than pot. The new Northwestern-Harvard study punches a hole in this conventional wisdom. Through three different methods of neuroimaging analysis, the scientists examined the brains of 40 young adult students from Boston-area colleges: 20 who smoked marijuana casually — four times a week on average — and 20 who didn’t use pot at all. Each group consisted of nine males and 11 females. The pot users underwent a psychiatric interview to confirm that they were not heavy or dependent marijuana users. “We looked specifically at people who have no adverse impacts from marijuana — no problems with work, school, the law, relationships, no addiction issues,” says Hans Breiter, a professor of psychiatry and behavioral sciences at the Feinberg School and co–senior author of the study. The scientists examined two key parts of the brain — the nucleus accumbens and the amygdala, which together help control whether people judge things to be rewarding or aversive and, in turn, whether they experience pleasure or pain from them. It is the development of these regions of the brain, Breiter says, that allows young people to expand their horizons, helping them appreciate and enjoy new foods, music, books and relationships. “This is a part of the brain that you absolutely never ever want to touch,” Breiter asserts. “I don’t want to say that these are magical parts of the brain — they are all important. But these are fundamental in terms of what people find pleasurable in the world and assessing that against the bad things.” Breiter and his colleagues found that among all 20 casual marijuana smokers in their study — even the seven who smoked just one joint per week — the nucleus accumbens and amygdala showed changes in density, volume and shape. The scientists also discovered that the more pot the young people smoked, the greater the abnormalities. 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. This is especially important, she and her colleagues add, in light of the growing push to legalize recreational marijuana use across America. “People think a little marijuana shouldn’t cause a problem if someone is doing O.K. with work or school,” Breiter says. “Our data directly says this is not so.” ## Transcript The time has come. The first marijuana commercial is due to air on major networks including Fox, CNN, Comedy Central and the Food Network. A company called the Marijuana Doctors, which connects medical marijuana patients with doctors, who can prescribe the drug. Claims that it's airing the first ever marijuana commercial on a major network. The ad draws a parallel between a shady street dealer trying to push unsafe sushi to unsuspecting buyers. And medical marijuana patients having to buy their medication on the street in a similar fashion. Take a look. Yo. You want sushi? I got sushi, I got the best sushi. This area is dry man, you know that, I know that, ain't nobody selling but me. I got tuna. I got salmon. I got sweet shrimp. I got the finest sashimi this area has seen in years. You need me and I need you. Let's make this work. You buy some sashimi, I'll throw in some rice paper man, totally free, gratis. I got everything. Even California rolls, baby. You wouldn't buy your sushi from this guy. So why would you buy your marijuana from him? Marijuanadoctors. com is the only service that connects patients with real doctors for medical marijuana recommendations. Simple, confidential, safe. Visit marijuanadoctors. com or call 1 866 996 9333. That's marijuanadoctors. com, 1 866 996 9333. 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