Genetic-environmental interaction in the genesis of aggressivity and conduct disorders

Familial aggregation of psychiatric disorders in a community sample of adolescents

OBJECTIVE

To determine whether specific psychiatric disorders and suicide attempts ascertained in a community sample of adolescents show evidence of familial aggregation.

METHOD

Fifty-eight adolescent probands recruited from the community and their relatives were assessed as to the presence of specific DSM-III Axis I disorders and suicide attempt, using a combination of family study and family history methodology.

RESULTS

In first-degree relatives, there was evidence for specific familial aggregation of suicide attempt (odds ratio [OR] = 12.1 95% confidence interval [CI] = 1.3 to 111.0), substance abuse (OR = 2.7, 95% CI = 1.1 to 6.7), and any Axis I disorder (OR = 2.5, 95% CI = 1.3 to 4.6), even after demographic confounders and familial comorbidity were controlled. Similarly, among second-degree relatives, in analyses controlling for potentials confounders, the disorders-specific aggregation of suicide attempt (OR = 12.3, 95% CI = 1.2 to 130.0), substance abuse (OR = 2.8, 95% CI = 1.6 to 4.8), and any Axis I disorder (OR = 1.5, 95% CI = 1.0 to 2.2) persisted.

CONCLUSIONS

The familial aggregation of suicide attempts and psychiatric disorders, particularly of substance abuse and any Axis I disorder, occurs in community samples and is not primarily attributable to referral status.

Minor physical anomalies: modifiers of environmental risks for psychiatric impairment?

OBJECTIVE

To test the hypothesis that minor physical anomalies (MPAs) modify an adolescent's vulnerability to environmental risk factors for psychopathology.

METHOD

One hundred eighteen unreferred male adolescents who had been evaluated as 7-year-olds received a comprehensive neuropsychiatric evaluation. The evaluation included standardized assessments of environmental risk factors for psychiatric impairment, neurological signs, IQ, MPAs, and psychiatric impairment. The relationship between psychiatric status and environmental risk was examined as a function of the MPA profile.

RESULTS

There was a significant interaction between MPAs and environmental risk in predicting psychiatric status. Environmental risk was more predictive of psychiatric impairment at age 17 in subjects with high scores on the MPA scale than in subjects with low scores on the scale. This relationship was particularly apparent in subjects with conduct disorder. MPAs also exhibited relationships with two childhood factors, neurological soft signs and Verbal IQ, that had been shown to predict adolescent psychopathology in prior reports on this cohort.

CONCLUSIONS

MPAs may contribute to psychiatric impairment by influencing an individual's vulnerability to environmental risk factors for psychopathology. These suggestive findings are consistent with an emerging body of literature examining the role of biopsychosocial interactions in psychiatric disorders.

Genetics and behavioral medicine

Genetics has substantial relevance to behavioral medicine. A rapidly growing body of evidence indicates the influence of genetics on health and disease and on the behavioral factors related to them. The model of quantitative genetics provides a general interpretational scheme for this burgeoning field. The model focuses on variability, and a major research objective is the decomposition of observed individual differences into portions attributable to various types of genetic and environmental sources of variability. This approach emphasizes the coaction of genes and environments and stands in sharp contrast to the archaic view that places nature and nurture in opposition. Some relevant examples are given in this first article to illustrate the general analytic process. A detailed application to cardiovascular health and disease is provided in the second article, and some policy implications are briefly considered in the third article.

An adoption study of drug abuse/dependency in females

In a sample of 102 women who had been adopted at birth, drug abuse/dependency was found by log-linear analyses to have a major pathway of genetic etiology that started with a biologic parent with antisocial personality and led to an adoptee with conduct disorder and then through aggressivity to drug abuse/dependency, as well as from conduct disorder directly to drug abuse. This result was similar to findings from a male sample collected from the same agencies and at the same time, wherein antisocial biologic parents produced aggressive and conduct-disordered off-spring, who in turn became drug abusers/dependents as adults. Results are compatible with family studies demonstrating that female drug abusers stem from deviant families and themselves demonstrate socially deviant behavior early in life. The present study shows that one element of familial factors is genetic, and that, in addition, the family environment directly affects behavior (aggressivity) that leads to drug abuse/dependency.