Data from WTP has recently been used to validate
the MacArthur Health and Behavior Questionnaire (HBQ),
a parent-report measure of child psychopathology.
This measure includes both ratings of emotional and
behavioral symptoms and ratings of the level of functional
impairment related to these symptoms.
Family resemblance in afternoon cortisol levels
was explained by shared environmental influences.
Further, the shared environment was found to account
for 62% of the variance in child cortisol levels and
only 14% in parent cortisol levels. Finally, cortisol
levels were found to decline with age up to approximately
nine-years-old, at which point they began to increase
with age (see figure below).
Auditory and tactile defensiveness were modestly
related to anxiety and fearful temperament. These
dimensions of defensiveness were largely distinct
from other common components of child adjustment however.
Twin correlations suggested that genetic factors exert
a moderate influence on both tactile and auditory
defensiveness and indicated that tactile defensiveness
may be more heritable than auditory defensiveness.
Genetic risk may interact with experience to predict
child internalizing symptoms.
Genetic risk was estimated based on co-twin mental
health status and zygosity. Monozygotic (MZ) co-twins
of high internalizers were considered to be at highest
genetic risk followed in descending order of risk
by dizygotic (DZ) co-twins of high internalizers,
DZ co-twins of low-moderate internalizers, and MZ
co-twins of low-moderate internalizers.
Experiential risk was estimated using a cumulative
risk index. Low socioeconomic status, living in a
single parent home, experiencing multiple negative
life events in the past year, having a high mother-rating
of the negativity of those life events, and exhibiting
a compromised style of mother-child interaction contributed
to the cumulative index.
Genetic risk was found to significantly interact
with experiential risk in the prediction of child
internalizing problems. That is, the association between
experiential risk and child internalizing was stronger
among those children at elevated genetic risk in comparison
to their low genetic risk counterparts (see figure