Marijuana and Teen Brains: A Risky Combination

Ventura County Releases Paper on Cannabis Consequences

OXNARD, Calif. – The Ventura County Behavioral Health Department today released a white paper focusing on “What the Science Says about Adolescent Use of Cannabis” which aims to inform parents, policy-makers and the general public about the risks of marijuana use by teens. The report is the second in a series of papers on substance use and addiction which reviews research about how brain functioning is affected by drugs.

“This is the second paper in our series, and it comes at a critical time of change in the field of addiction,” said Patrick Zarate, Chief Operations Officer for the Behavioral Health Department, and Alcohol and Drug Programs Division Manager. “As cannabis is more widely discussed, the public really needs reliable information about the risks,” he said, “While marijuana may well become legal in the near future, that doesn’t make it safe.”

A review of Ventura County youth treatment program data showed that 98 percent of adolescents in treatment had used cannabis and the majority of them started by age 13. This “early onset” of drug use is troubling to behavioral health experts because it is one of several key risk factors for development of cognitive deficits and psychotic disorders, according to author, Dr. Linda Gertson, a licensed psychologist and former Treatment Services manager for Alcohol and Drug Programs. “For the local youth who reported use of drugs in addition to cannabis, use typically began one to three years after the onset of cannabis use,” she said. “Multiple peer-reviewed studies have shown that early and heavy use can be harmful, and delaying use to the mid-twenties may be protective.”

In one such study, while only 4.4 percent of individuals who began smoking cannabis after age 21 became addicted within the first two years, 17.4 percent of 13-year-olds became addicted within the same time period (Winters and Lee, 2008).

Other studies have shown that between 25-50 percent of people who use cannabis on a daily basis become addicted, and that early and heavy use increases the risk of use and addiction to other drugs (Hall and Degenhardt, 2009).

“It doesn’t stop there,” said Zarate. “Adolescent use also appears to produce cognitive impairment, diminish educational attainment compared to non-users, and it roughly doubles the risk of experiencing a psychotic disorder like schizophrenia, especially if there is a family history.”

Officials are quick to point out that the question “Does cannabis use cause schizophrenia?” might be phrased more appropriately as “What are the risk factors that link cannabis use and psychotic disorders like schizophrenia?,” which include early onset of cannabis use, high frequency of use, genetic predisposition and family history of psychoses.

According to Gertson, “The majority of experts referred to emphasize the need to deter and delay use of cannabis during adolescence because of the studies which show regular teen use is associated with possible long-term harms. People should read it themselves.” For more information go to:

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