Subject:
Substance Abuse

Short Description:

Daily Marijuana Use by Teens Creates Life Problems

Background:

A new study provides strong evidence that chronic marijuana use during adolescence can lead to significant social and psychiatric issues later in life.

Researchers performed a meta-analysis of three longitudinal studies (conduced in Australia or New Zealand) that measured the association of marijuana use with a variety of potential negative outcomes. The studies measured frequency of use before 17 years of age (never, less than monthly, monthly or more, weekly or more, or daily). The number of participants varied depending on the outcome being measured from 2,537 to 3,765 teens.

Seven potential outcomes were measured: completion of high school, receiving a university degree, dependence on marijuana, use of other illicit drugs, suicide attempts, development of depression, and dependence on welfare. The study by researchers in Australia and New Zealand found that teens who use marijuana daily before age 17 are 63% less likely to get a high school diploma than those who never used cannabis and are 18 times more likely to become dependent on the drug. In the United States, about 7% of high school seniors are daily or near-daily marijuana users, according to a 2013 survey.

There were clear and statistically significant associations between frequency of use and five of the adverse outcomes. Those who were daily users before age 17 were less likely than non-users to complete high school or to attain a university degree, and far more likely to become dependent on cannabis, use other illicit drugs, and attempt suicide.

These associations do not necessarily prove causality, because it’s possible that unidentified factors may lead to these negative outcomes. Nonetheless, the researchers controlled for many possible confounding factors, and found a dose response relationship (the heavier the marijuana use, the stronger the associations).

Given the growing movement to decriminalize or legalize marijuana use in several US states, as well as some Latin American countries, the researchers said those efforts should be carefully assessed to ensure they don’t increase adolescent marijuana use and the potentially adverse effects (Silins E et al, Lancet Psychiatry 2014:1(4):286–293).

CCPR’s Take: While not definitive, this is the most compelling evidence yet that daily pot smoking is bad for teens in the long-term.