--- description: Using pot, cannabis and marijuana, even over decades was only linked to one negative health effect in a new study: poor periodontal health. title: Long-Term Pot Smoking Doesn’t Harm Health image: https://static.time.com/v3/assets/bltea6093859af6183b/bltd4cec7403db29088/698896c3a988cac3446b8231/cannabis.jpg?branch=production&width=3840&quality=75&auto=webp&crop=16:9 ---  * [Health](/section/health/) ## Health Update your preferences in [Account Settings](/account/preferences/) Close * [Research](/tag/research/) ## Research Update your preferences in [Account Settings](/account/preferences/) Close # Long-Term Pot Smoking Doesn’t Seem to Harm Health: Study ## Video: Watch: Inside One of New York’s First Medical Marijuana Dispensaries [Watch (HLS stream): Watch: Inside One of New York’s First Medical Marijuana Dispensaries](https://cdn.jwplayer.com/manifests/8UkmeWNa.m3u8) (2:15)  _Published 2016-01-22. Tour one of the five facilities that will provide cannabis for medical purposes_  by [Mandy Oaklander](/author/mandy-oaklander/)  ## Mandy Oaklander Update your preferences in [Account Settings](/account/preferences/) Close Oaklander is a senior editor at TIME. Jun 7, 2016 3:37 PM CUT  Getty Images  by [Mandy Oaklander](/author/mandy-oaklander/)  ## Mandy Oaklander Update your preferences in [Account Settings](/account/preferences/) Close Oaklander is a senior editor at TIME. Jun 7, 2016 3:37 PM CUT Even after years of heavy use, marijuana doesn’t seem to have much of an impact on the physical health of the body. So finds a recent [study published in _JAMA Psychiatry_](https://archpsyc.jamanetwork.com/article.aspx?articleid=2526003 "undefined"), which analyzed data from a group of 1,037 New Zealanders followed from their birth until age 38\. The researchers, led by Madeline Meier of Arizona State University, looked at whether cannabis use from age 18 to 38 was linked to several aspects of physical health, which were measured at several points throughout the years of the study through lab tests and self-reports. The only bad effects pot seemed to have were on the teeth. At age 38, people who used cannabis had worse periodontal health than their peers, and nothing else appeared to be affected. By contrast, tobacco use was connected to all the expected declines: worse lung function, more inflammation and compromised metabolic health. Of course, the results come with a caveat; it’s possible that negative health effects of cannabis could show themselves after the age of 38. Even more surprisingly, the researchers found that cannabis use over time was linked to a lower BMI, smaller waist circumference and better HDL cholesterol, suggesting that cannabis may be involved in metabolism. But it’s unlikely that this would have a major effect, the study authors note, since pot wasn’t linked to reduced risk of metabolic syndrome. “There are definitely health risks associated with heavy marijuana use, but there just aren’t as many as we previously thought,” says Dr. Kevin Hill, a marijuana addiction expert and assistant professor of psychiatry at Harvard Medical School, whose [new commentary](http://jama.jamanetwork.com/article.aspx?articleid=2526619 "undefined") on the study is published Tuesday in _JAMA_. The same group of researchers discovered some of those health risks in their [famous 2012 study](http://healthland.time.com/2012/08/28/does-weekly-marijuana-use-by-teens-really-cause-a-drop-in-iq/ "undefined"). Using data from the same group of New Zealanders, Meier and her team found that heavy marijuana use had effects on the brain on teenagers. Using cannabis regularly was associated with up to an 8 point decline in IQ when people started before age 18\. (When adults began using cannabis after age 18—even heavily—they didn’t see this decline.) “The answers with marijuana aren’t exactly what we would have expected them to be, and this is a great example,” Hill says. “You need to be willing to change your mind on these issues.” ```json [{"@context":"https://schema.org","@type":"NewsArticle","@id":"https://time.com/4359757/pot-smoking-marijuana-cannabis-health/","mainEntityOfPage":{"@type":"WebPage","@id":"https://time.com/4359757/pot-smoking-marijuana-cannabis-health/"},"headline":"Long-Term Pot Smoking Doesn’t Seem to Harm Health: Study","datePublished":"2016-06-07T15:37:36.000Z","dateModified":"2026-02-22T22:26:23.926Z","description":"Using pot, even over decades, was only linked to one negative health effect in a new study","url":"https://time.com/4359757/pot-smoking-marijuana-cannabis-health/","keywords":["Research"],"thumbnailUrl":"https://static.time.com/v3/assets/bltea6093859af6183b/bltd4cec7403db29088/698896c3a988cac3446b8231/cannabis.jpg?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","author":[{"@type":"Person","name":"Mandy Oaklander","jobTitle":"Oaklander is a senior editor at TIME.","url":"https://time.com/author/mandy-oaklander/"}],"articleSection":"Health","image":[{"@type":"ImageObject","url":"https://static.time.com/v3/assets/bltea6093859af6183b/bltd4cec7403db29088/698896c3a988cac3446b8231/cannabis.jpg?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","width":1200,"height":675,"headline":"cannabis","caption":"cannabis","creditText":"Getty Images","representativeOfPage":true}],"publisher":{"@type":"Organization","name":"Time","url":"https://time.com/","logo":{"@type":"ImageObject","url":"https://time.com/images/logo.png","width":528,"height":156},"foundingDate":"March 3, 1923","sameAs":["https://www.facebook.com/time","https://www.instagram.com/time/?hl=en","https://twitter.com/time","https://www.pinterest.com/timemagazine"]}},{"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"/section/health/","name":"Health"}},{"@type":"ListItem","position":2,"item":{"@id":"/tag/research/","name":"Research"}},{"@type":"ListItem","position":3,"item":{"@id":"https://time.com/4359757/pot-smoking-marijuana-cannabis-health/","name":"Long-Term Pot Smoking Doesn’t Seem to Harm Health: Study"}}]},{"@context":"https://schema.org","@type":"VideoObject","name":"Watch: Inside One of New York’s First Medical Marijuana Dispensaries","description":"Tour one of the five facilities that will provide cannabis for medical purposes","thumbnailUrl":"https://cdn.jwplayer.com/v2/media/8UkmeWNa/poster.jpg?width=720","uploadDate":"2016-01-22T18:39:32.000Z","contentUrl":"https://cdn.jwplayer.com/manifests/8UkmeWNa.m3u8","embedUrl":"https://time.com/4359757/pot-smoking-marijuana-cannabis-health/","duration":"PT2M15S","potentialAction":{"@type":"SeekToAction","target":"https://time.com/4359757/pot-smoking-marijuana-cannabis-health/?jw_start={seek_to_second_number}","startOffset-input":"required name=seek_to_second_number"}}] ```