The mental health and well-being of adolescents with/without intellectual disability in the UK.

Aims: To estimate the self-reported and parent-reported mental well-being of adolescents (aged 14 and 17) with/without intellectual disability in a sample of young people representative of the UK population.

Methods: Secondary analysis of data collected in Waves 6 and 7 of the UK's Millennium Cohort Study. The analytic sample consisted of 10,838 adolescent respondents at age 14 (361 with intellectual disability and 10,477 without) and 9,408 adolescent respondents at age 17 (292 with intellectual disability and 9,116 without).

Results: Parental reports of adolescent problems on the Strengths and Difficulties Questionnaire (SDQ) indicated that adolescents with intellectual disability at ages 14 and 17 were more likely to have problems than those without intellectual disability across all SDQ domains. Adolescent self-report data at age 17 indicated that adolescents with intellectual disability were more likely to (self)-report that they had problems than those without intellectual disability on all but one SDQ domain. The magnitude of relative inequality between those with and without intellectual disability was consistently lower for self-report than parental report. On indicators of depression, mental well-being, self-harm, positive mental health, happiness and general psychological distress at ages 14 and 17, we found no self-reported group differences between adolescents with and without intellectual disability.

Conclusions: Further research is needed to understand: (1) why the magnitude of mental health inequalities between those with and without intellectual disability on the SDQ may be dependent on the identity of the informant; and (2) whether such differences are also apparent for other measures of mental health or well-being.