Child sex and respiratory sinus arrhythmia reactivity as moderators of the relation between internalizing symptoms and aggression.

Previous studies have examined sex differences in physiological responding, including respiratory sinus arrhythmia (RSA) reactivity in response to changing stimulus conditions involving situation specific or gender related cues, in children and adolescents. The present study examined whether RSA reactivity moderates the relation between aggression and internalizing symptoms and whether there are sex differences in this effect. Participants were 82 adolescents (M age = 12.1 years; 44 girls) from the general middle-school population. Peer nominations assessed aggression and internalizing symptoms, and RSA reactivity (defined as change in RSA from baseline to task) was recorded while participants anticipated and responded to an 85 dB signaled white-noise burst. For girls, internalizing symptoms were associated with aggression only if girls showed low RSA reactivity from baseline to task; there was no effect for boys. This association was absent when girls showed high RSA reactivity. Thus, child sex appears to influence not only levels of physiological responding but also relations of physiological responding to comorbidity of adjustment problems.