Problem behavior of individuals with Down syndrome in a nationwide cohort assessed in late adolescence.

OBJECTIVE: To assess problem behavior in adolescents with Down syndrome and examine the association with sex and severity of intellectual disability. STUDY
DESIGN: Cross-sectional data of a Dutch nationwide cohort of Down syndrome children aged 16-19 years were collected using a written parental questionnaire. Problem behavior was measured using the Child Behavior Checklist and compared with normative data. The degree of intellectual disability was determined using the Dutch Social competence rating scale.
RESULTS: The response rate was 62.8% (322/513), and the mean age 18.3 years (SD ± 0.8). The total score for problem behavior was higher in adolescents with Down syndrome than in adolescents without Down syndrome (26.8 vs 16.5; P < .001). Overall, 51% of adolescents with Down syndrome had problem scores in the clinical or borderline range on 1 or more Child Behavior Checklist subscales; this is more than twice as high as adolescents without Down syndrome. Adolescents with Down syndrome had more internalizing problems than their counterparts without Down syndrome (14% and 9%, respectively, in the clinical range); the percentages for externalizing problems were almost equal (7% and 9%, respectively, in the clinical range). The highest problem scores in adolescents with Down syndrome were observed on the social problems and thought problems subscales (large to very large standardized differences). Male sex and/or more severe mental disabilities were associated with more behavioral problems.
CONCLUSIONS: Serious problem behavior is more prevalent in adolescents with Down syndrome. This demonstrates the need for a focus on general behavior improvement and on the detection and treatment of specific psychopathology in individuals with Down syndrome.