Child Psychopathology: Heritability and Parental Differential Treatment

Because behavioral problems impede healthy, independent functioning, understanding the etiology of child psychopathology is important. Many studies of child psychopathology have examined relations between parenting factors and internalizing and externalizing disorders, but few have examined links between differential treatment (DT) of siblings and symptoms. 374 monozygotic and dizygotic twin pairs sampled from the Wisconsin Twin Project were assessed for internalizing, externalizing, and attention deficit hyperactivity disorder (ADHD) symptoms with the MacArthur Health and Behavior Questionnaire (HBQ). Composites of DT were created from mother and father reports of discipline, attention, and affection on the Differential Treatment Questionnaire (DTQ) and mother and twin reports on the Sibling Relationship Questionnaire (SRQ). Children responded to the SRQ individually through puppet interviews. Observed mother's warmth, intrusiveness, and hostility toward each twin during videotaped interactions were included as objective measures. Analyses were conducted with a sample of one randomly selected twin from each pair and then replicated with cotwins. Primarily, do different reporters agree on magnitude and direction of DT, and do observations of DT support these claims? Parents reported similar levels of differential attention, affection, and discipline on the DTQ (mean r = .34, p < .01). Children reported higher levels of DT in mothers t(133) = -5.58, p < .01; t(131) = -4.63, p < .01 and fathers, t(121) = -5.45, p < .01; t(137) = -6.67, p < .01 . Observed and family-reported measures exhibited little agreement, with the exception of maternal intrusiveness' relation to mother- reported discipline (r = .15, p < .05). Secondly, does DT predict psychopathology symptoms? The most reliable predictor of internalizing, externalizing, and ADHD symptoms was maternal differential discipline on the DTQ, Beta = .22, p < .01. Further, observed differential intrusiveness significantly predicted ADHD, even when the overall shared level of intrusiveness between twins was first controlled Beta = .17, p = .02. Finally, to what extent do genes and the environment influence these variables? Psychopathology symptoms were moderately to highly heritable (.67-.73), but heritable traits of the child did not influence maternal hostility and intrusiveness in observed interactions. Siblings do experience DT, and that these differences predict symptoms of childhood psychopathology.