A longitudinal biosocial study of cortisol and peer influence on the development of adolescent antisocial behavior.

It is increasingly recognized that in order to understand the complex phenomenon of antisocial behavior, interrelations between biological and social risk factors should be taken into account. In the current study, this biosocial approach was applied to examine the mediating role of deviant peers in longitudinal associations linking the level of hypothalamic-pituitary-adrenal (HPA) axis activity to aggression and rule-breaking. Participants were 425 boys and girls from the general population, who were assessed yearly at ages 15, 16, and 17. As a measure of HPA axis activity, cortisol was assessed at awakening, 30, and 60 min later (the cortisol awakening response, CAR). Participants, as well as their best friend, reported on their own aggressive and rule-breaking behavior, thereby allowing to assess bidirectional influences within friendships. Aggression was only predicted by a decreased cortisol level at awakening, and not by aggressive behavior of their friend. Decreased levels of cortisol at awakening predicted adolescents' rule-breaking, which subsequently predicted increased rule-breaking of their best friend. The latter was only found for adolescents who changed friends, as compared to adolescents with the same friend in every year. Gender differences were not found. These findings suggest that interrelations between biological and social risk factors are different for the development of aggression versus rule-breaking. Furthermore, decreased levels of HPA axis activity may represent a susceptibility to selecting deviant peers.

Carrier detection in X-linked retinitis pigmentosa by multipoint DNA analysis. Problems due to genetic heterogeneity.

DNA diagnosis of X-linked retinitis pigmentosa (XLRP) is hampered by its genetic heterogeneity, while a clinical subdivision is almost impossible to make. So far, diagnostic services have been offered only to those families in which linkage to one RP locus (RP2 or RP3) has been clearly established. In most families, however, the nature of the XLRP type cannot be distinguished on the basis of linkage analysis. Here the authors describe that in some families DNA diagnosis is nonetheless feasible, when polymorphic DNA markers are used which span the entire Xp21.1-Xcen region and when no recombination between these markers disturbs the phase.