Engaging in sexual behavior and/or drug use places adolescents, especially girls, at risk for future depression, according to a study in the October American Journal of Preventive Medicine. Denise D. Hallfors, PhD, and colleagues found that depression did not predict behavior, which contradicts the widely held notion that some teens may use alcohol, drugs, and/or sex to self-medicate depressed feelings. Instead, there was strong evidence that heavy marijuana use and binge drinking increased the likelihood of depression among boys and that any alcohol, drug, or sexual experimentation increased the likelihood of depression for girls.

“Many clinicians believe that a major cause of substance use among adolescents is self-medication of depression,” Dr. Hallfors told NeuroPsychiatry Reviews. “Our recent research suggests that this may not be true. We found in a large, longitudinal cohort study that behavior patterns of substance use and sexual behavior precede depression rather than vice versa. We also found that the relationship between substance use and depression was different for boys and girls. Girls increase their risk of depression when they experiment with either substance use or sexual intercourse; boys increase their risk with regular tobacco or marijuana use and with binge drinking. Critical next steps in research will be to test whether stopping substance use and sexual behavior ameliorates depression for adolescents.” Dr. Hallfors is a Senior Research Scientist at the Pacific Institute for Research and Evaluation and an Adjunct Professor at the School of Public Health, University of North Carolina at Chapel Hill.

The study included more than 13,000 youths in grades 7 to 11 and compared depression with abstinence and with both experimentation and high-risk involvement with alcohol, tobacco, other drugs, and sexual behavior. To determine whether sexual activity or alcohol and drug use came first, the researchers analyzed data to see whether any of these behavior patterns in the first year were more likely to result in depression the next year. The data were from the National Longitudinal Study of Adolescent Health, weighted to produce population estimates. Multivariate logistic regression analyses were conducted to test temporal ordering, controlling for covariates. The main outcome measures were depression, as measured by a modified Center for Epidemiological Studies–Depression Scale, and three behavior patterns—abstaining from sexual intercourse and drug use, experimental behavior patterns, and high-risk behavior patterns.

RISKY BEHAVIOR AND DEPRESSION

Overall, the researchers found that sexual activity and drug use predicted an increased likelihood of depression, but depression did not predict behavior. Among girls, both experimental and high-risk behavior patterns predicted depression. For boys, only high-risk behavior patterns increased the odds of later depression. Girls who experimented with tobacco, alcohol, or drugs were more than twice as likely to be depressed as girls who abstained from using these substances and three times more likely to be depressed if they had sex. Boys who only experimented with such behaviors did not increase their likelihood for depression. However, boys were more likely to be depressed if they were high-risk users: Binge drinkers were four-and-a-half times more likely to be depressed than were abstainers, and daily marijuana smokers were three to four times more likely to be depressed than were abstainers. Depression did not predict behavior in boys or experimental behavior in girls, but it decreased the odds of high-risk behavior among abstaining girls and increased the odds of high-risk behavior among girls already experimenting with substance use. Teens who abstained from sex, alcohol, drugs, and tobacco had very low rates of depression the second year of the study: about 4% for both boys and girls.

DEPRESSION AND GENDER

Because patterns of relationships between risky behaviors and depression vary for boys and girls, implications for prevention, intervention, and treatment should also vary, Dr. Hallfors reasoned. She said that the findings indicate that patterns of substance abuse, especially binge drinking and frequent marijuana use, increase the likelihood of depression in boys by more than fourfold. Therefore, boys who are heavy users of alcohol or marijuana should be counseled to reduce or stop use and should be screened for depression. Moreover, when boys present with depression, she advised clinicians to screen for and aggressively treat substance abuse and addiction.

The investigators found that for females, even modest involvement in substance use and sexual experimentation elevated depression risk. The study’s findings are consistent with existing theoretical perspectives that suggest girls’ greater interpersonal sensitivity contributes to higher levels of interpersonal stress during adolescence. Therefore, the greater exposure to stress due to risky behavior, as well as girls’ more negative reactivity to interpersonal stressors, may partially account for demonstrated gender differences in rates of depression. It has been long recognized that depression prevalence increases in adolescence, particularly for girls, and that links exist between depression and risky behaviors. Existing theories have assumed that hormonal changes experienced during adolescence put females at greater risk and that youths “self-medicate” depression with drugs and sex. However, this study finds little to support these prevailing theories, noted Dr. Hallfors.

Odds ratios for predicting depression in one year for participants who both smoked and engaged in sexual activity were 3.05 for boys and 2.72 for girls. For those who used alcohol and engaged in sex, the ratios were 2.83 for boys and 2.61 for girls. For binge drinkers, the ratios were 4.56 for boys and 2.03 for girls. For marijuana users, the ratios were 3.37 for boys and 1.99 for girls. For those who had sex with multiple partners, the odds ratios were 2.35 for boys compared with 10.90 for girls, and for IV drug users, the ratios were 2.47 for boys and 7.53 for girls.

Dr. Hallfors recommended that girls who are engaging in substance use or sexual intercourse should be screened for depression and provided with anticipatory guidance about mental health risks associated with these behaviors. She added that girls who are depressed should be carefully assessed for involvement in these behaviors and that treatment should include counseling about drug use cessation and sexual decision-making.

Dr. Hallfors cautioned that future research is needed to better understand the mechanism of the relationship between adolescent behavior and depression and to determine whether interventions to prevent or stop risky behaviors will also reduce the risk of later depression.

—Christine DeFranco

Suggested Reading
Hallfors DD, Waller MW, Bauer D, et al. Which comes first in adolescence—sex and drugs or depression? Am J Prev Med. 2005;29:163-170.

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