Child Psychopathology: Heritability and Parental Differential Treatment
Ficks, Courtney; Doelger, Lisa; Horowitz, Karina R.; and Lemery-Chalfant, Kathryn
Department of Psychology, Arizona State University
Because behavioral problems impede healthy functioning, we must understand the etiology of child psychopathology. Many studies have examined relations between parenting factors and internalizing and externalizing disorders; 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. Composites were created from mother and father reports of differential discipline, attention, and affection on the Differential Treatment Questionnaire (DTQ) and mother and twin reports on the Sibling Relationship Questionnaire (SRQ). Observed maternal behaviors toward each twin during videotaped interactions were included as objective measures.
Mothers and fathers reported similar levels of DT on the DTQ (mean r = .34, p < .01). Children reported higher levels of DT than 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. The best predictor of all symptoms was maternal differential discipline on the DTQ, Beta = .22, p < .01. Observed differential intrusiveness predicted ADHD, even when the shared level of intrusiveness between twins was first controlled Beta = .17, p = .02. Symptoms were moderately to highly heritable (.67-.73), yet heritable traits of the child did not influence maternal behavior in observed interactions. Siblings do experience DT, and these differences predict childhood psychopathology symptoms.