Diana Zuckerman, Ph.D. and Padma Ravichandran
Marijuana has traditionally been considered less worrisome than other illegal drugs, but the costs to our society may be higher than you think. When marijuana use among youth increased dramatically in the 1990s, many adults of the baby boomer generation, including most parents, were not very worried, in spite of numerous reports and widespread media attention. However, by 1999, when the percentage of 9th through 12th graders who have used marijuana one or more times peaked at 47%, the American Academy of Pediatrics (AAP) released a policy statement, calling marijuana use by adolescents a “major health problem.”  AAP recommended that pediatricians “counsel young people against any use of the drug,” and warned that “heavy marijuana use may be especially dangerous for adolescents during puberty.” The AAP statement concluded that marijuana is addictive, adding that teenagers who are dependent on the drug should be offered treatment options.
There are many changes in society that may have an impact on marijuana use among youth. For instance, marijuana web sites make it easy to purchase marijuana seeds, pipes, and water pipes that cool and concentrate the smoke, as well as get growing instructions. These web sites, along with the legalization of medical marijuana in many states, may send kids the message that marijuana use is safe.
In spite of these changes, however, the U.S. has seen a decline in marijuana use among youth over the last decade. By 2007, the percentage of 9th through 12th graders who had ever tried or used marijuana had dropped to 38%. And according to the 2008 National Survey on Drug Use and Health, 7% of kids age 12-17 used marijuana in the past month, down from 8% in 2002. While this is reassuring, parents still need to be reminded that the marijuana of today is much different from the drug of a generation or more ago. For instance, very strong seedless marijuana is readily available in towns, suburbs and cities across the country. Experts at the National Institute on Drug Abuse say that marijuana today may be up to five times as strong as what was available 30 or more years ago.
As marijuana has become a more powerful drug, experts are seeing an increase in addiction to it and related drugs like hashish-from 13% in 1997 to 17% in 2008. According to a 2008 report by the Substance Abuse and Mental Health Services Administration, more adults are now seeking treatment for their addictions to marijuana and hashish than to drugs like cocaine (11%) or heroine (14%). 
There are growing concerns about the short-term dangers of marijuana use among youth, as well as the long-term health risks, such as cancer. The short-term dangers include but are not limited to memory loss, distorted perception, trouble with thinking and problem solving, loss of motor skills, and increased heart rate. As teens get older, other short-term dangers may arise from marijuana use. It has a very negative effect on driving, for instance. In a road test, reaction time increased 36 percent, which would result in driving an additional 139 feet before stopping if the person was driving 59 miles per hour. And infants born to mothers who smoke marijuana during pregnancy are shorter, weigh less, and have smaller heads.
The long-term health risks include lower attention levels later in life, cancer, and weakened executive function. Smokers can’t process newly learned information and store it for later use. Several studies indicate the loss of “executive functions” such as learning lists and doing homework, and that this continues when the individual is no longer high. One recent study found that young stroke patients (ages 18-55) were more likely to be current pot smokers than people of the same age, race, and sex who did not have a stroke. However, that study did not evaluate whether the patients had smoked marijuana for the years prior to their current medical exams, or only around the time of the stroke.
For years, marijuana has been called a “gateway drug” or a stepping stone to even more harmful and addictive substances. A study of 2,765 pairs of twins examined this progression from “softer” drugs to harder, while controlling for all the factors that twins have in common, such as genes, personality traits, home environment and (for the most part) access to drugs. They found that men and women who used marijuana or hashish before age 17 were more than twice as likely as others to ever become dependent on alcohol or to abuse any illegal drugs. Specifically, they were twice as likely to ever use marijuana/hashish, more than twice as likely to abuse sedatives, four times as likely to abuse stimulants or cocaine, and almost four times as likely to abuse heroin or other opiates. This was true whether the twins were identical or not.
 Centers for Disease Control. Trends in the Prevalence of Marijuana, Cocaine, and Other Illegal Drug Use. The national Youth Risk Behavior Survey (YRBS): 1991-2007. Retrieved on May 27, 2010, from http://www.cdc.gov/HealthyYouth/yrbs/pdf/yrbs07_us_drug_use_trend.pdf
 Substance Abuse and Mental Health Administration. (2008). Results from the 2008 national survey on drug use and health: National findings. Retrieved on 13 Apr 2010, from the Substance Abuse and Mental Health Services Administration website: http://www.oas.samhsa.gov/nsduh/2k8nsduh/2k8Results.pdf
 National Institute on Drug Abuse. (2005) Marijuana Abuse, Research Report Series. Retrieved on May 26, 2010 at http://www.nida.nih.gov/ResearchReports/Marijuana/default.html
 Substance Abuse and Mental Health Services Administration.(2008). National Admissions to Substance Abuse Treatment Services, Treatment Episode Data Set (TEDS) 1998 – 2008. Retrieved on May 26, 2010 from http://wwwdasis.samhsa.gov/teds08/teds2k8natweb.pdf Kaiser, C. (2013.) Is Pot Smoking a Trigger? Med Page Today. Retrieved 6 February 2013 from http://www.medpagetoday.com/MeetingCoverage/ISC/37206?utm_content=&utm_medium=email&utm_campaign=DailyHeadlines&utm_source=WC&xid=NL_DHE_2013firstname.lastname@example.org&mu_id=5519940.