Preteen Marijuana Use Linked to Comorbid Substance Abuse and Psychological Disorders

From Medscape Medical News
Barbara Boughton

April 22, 2010 (San Francisco, California) — One of the largest studies to date of preteen marijuana users has found that those who start smoking the drug before age 13 years have an increased risk for comorbid substance abuse and psychosocial and legal problems, according to research presented here at the American Society of Addiction Medicine 41st Annual Medical-Scientific Conference.

In the study of 136 substance-dependent girls and boys, those who started using marijuana as a preteen were more likely to have a history of posttraumatic stress disorder (PTSD), suicide attempts, and traffic violations and to be dependent on other drugs.

"Our study supports a significant relationship between preteen marijuana use and poor outcomes. Its strengths include the fact that it is the largest clinical sample to date balanced by gender," lead researcher Youssef Mahfoud, MD, from the Department of Psychiatry at Case Western Reserve and University Hospitals Case Medical Center, Cleveland, Ohio, told Medscape Psychiatry.

First Drug of Abuse

In the study of substance-dependent youths in treatment (age range, 14 - 18 years), characteristics of those who started using marijuana before age 13 years were compared with those who started using the drug after that age.

In comparison with those who started as teenagers, children who started using marijuana as preteens were more likely to be dependent on hallucinogens (44% vs 27%; P < .05) and to have comorbid substance abuse disorders (M = 3.42 vs 2.59; P < .05).

Those who began using marijuana before age 13 years also had higher rates of PTSD (16% vs 6%; P < .05), a history of attempting suicide (32% vs 19%; P < .05), and a history of traffic violations (7% vs. 1%; P < .05). In addition, preteen marijuana users were also more likely to have used marijuana as their first drug of abuse (55%), rather than alcohol.

To determine whether there were any factors that predicted preteen marijuana use, the authors also looked at ethnicity, race, parental education, parental substance abuse history, and characteristics of preteen marijuana users on admission to substance abuse programs.

Those who started using marijuana as preteens were more likely to be younger when entering treatment and to be marijuana dependent on admission. There was also a trend toward a greater risk for nicotine addiction, Dr. Mahfoud said.

Preteen marijuana abusers were more likely to be Hispanic (14% vs 3%). Those who used marijuana as a preteen also tended to have parents with less education. Sixty percent of those who started using marijuana as a preteen had parents with just a junior high education compared with 47% of those who started as teenager.

Important Implications

The study has important implications for societal interventions, Dr. Mahfoud said. Preteens with parents who have less education, who are vulnerable because of PTSD or suicide attempts, or who are identified as heavy nicotine users might be targeted for interventions aimed at preventing marijuana use, he added.

The researchers plan to follow the sample in the study to see whether they find an improvement in outcomes for preteen marijuana users after substance abuse treatment and to gauge whether preteen marijuana use is associated with less successful response to substance abuse treatment therapies.

"Addiction is a disease of adolescent onset when children's brains are growing rapidly," said Gavin Bart, MD, director of the Division of Addiction Medicine at the Hennepin County Medical Center and assistant professor of medicine at the University of Minnesota Medical School, Minneapolis, Minnesota. Dr. Bart chaired the American Society of Addiction Medicine meeting and moderated the session at which the Case Western Reserve study was presented.

"So it's extremely helpful for those who treat substance abuse to know what the risk factors are for early marijuana use, and to use that information to identify patients at risk," he added.

"This is one of the first studies to look at preteens in clinical treatment, and to show that those who start using marijuana as a preteen have more problems controlling marijuana use and other drugs later in life. It reinforces the concept that prevention does not need to start in junior or senior high, but in grade school," commented Timothy Fong, MD, assistant professor of psychiatry and codirector of the addiction medicine clinic at the University of California–Los Angeles. "However, this is not evidence that marijuana is a gateway drug," he cautioned. "It does not show causality."

The study was supported by grants from the National Institute on Alcohol Abuse and Alcoholism and the John Templeton Foundation. Dr. Fong has disclosed being on speakers' bureaus for Reckitt-Benckiser, Pfizer Pharmaceuticals, and Lilly Pharmaceuticals. Dr. Mahfoud and Dr. Bart have disclosed no relevant financial relationships.

American Society of Addiction Medicine 41st Annual Medical-Scientific Conference: Abstract 2. Presented April 16, 2010.