Conduct disorder and alcoholism in teens

Dec 30 2004

While teenagers who drink also tend to have behavior problems, there is more of a genetic basis to their conduct than there is to the lure of alcohol, a new study on 14-year-old Finnish twins reports.

The alcohol abuse appears to stem from environmental causes, the researchers say.

Many studies have noted a link between bad conduct and alcohol problems, but exactly how they are related is not fully understood. In the past, bad parenting got the brunt of the blame for conduct disorder but it is now recognized that the disorder - like alcoholism in adults - probably also has a genetic cause.

"The severity of problems that adolescents with conduct disorder experience in school adjustment and home functioning underscores the need to understand better its causes and its relationship with alcohol abuse," says study author Richard J. Rose, Ph.D., of the Department of Psychology at Indiana University in Bloomington and the Department of Public Health at the University of Helsinki in Finland.

Young people with conduct disorder engage in behaviors like bullying, stealing, running away from home, fire-setting, destroying property and engaging in cruelty to animals or people.

Rose and colleagues conducted face-to-face interviews with nearly 2,000 twins at age 14. By comparing fraternal twins with the more genetically similar identical twins, Rose and colleagues hoped to discover the relative environmental and genetic underpinnings of conduct disorder and alcoholism.

They also administered a questionnaire to the twins' parents to determine the existence of any familial alcohol problems and contacted schools to get teacher and peer ratings on the twins.

Symptoms of conduct disorder were common, reported by nearly half of the study participants, and 12 percent of the twins were diagnosed with full-blown conduct disorder. Genes played a significant role in these symptoms, especially among girls, Rose and colleagues found.

Rose says that although the occurrence of conduct disorder symptoms seems high, it is not far off-base given the prevalence of misconduct by young people.

"I think the prevalence of conduct disorder symptoms is higher in this sample than would be expected in a random one," Rose says. "But a single symptom of [conduct disorder] is not uncommon, even in a random sample of young adolescents."

Alcohol abuse problems were comparatively rare among the study participants. Also, the researchers found no genetic underpinning for alcohol abuse; that is, identical and fraternal twins exhibited similar behavior patterns. They did find conduct disorder to be significantly linked with alcohol abuse - that is, twins with conduct disorder symptoms were more likely to have alcohol abuse problems, and vice versa - but this link was due to the environment the twins lived in, not due to genes.

The study results appear in the journal Alcoholism: Clinical and Experimental Research.

If the study participants had been older, a genetic influence on alcoholism would have been noted, according to the study. "That we found no genetic effects on symptoms of alcoholism must be understood in the context of the youthful age of our interviewed twin sample," Rose says. "Significant genetic effects on patterns of use and abuse of alcohol among Finnish twins are detectable in middle to late adolescence."

The researchers speculate that conduct disorder may be an earlier manifestation of genetic dispositions that later contribute to alcoholism. "Early identification of adolescents at risk for development of alcoholism might focus on symptoms of conduct disorder to offer opportunities for targeted intervention," Rose says.

This research was supported by National Institute of Alcohol Abuse and Alcoholism, the Academy of Finland, and the Yrjö Jahnsson Foundation.

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