Measurement invariance of the strengths and difficulties questionnaire across socioeconomic status and ethnicity from ages 3 to 17 years: A population cohort study.

Mental health inequalities along ethnic and socioeconomic groupings are well documented. The extent to which these observed inequalities are genuine or reflect measurement differences is unclear. In the current study we sought to investigate this in a large population-based sample of children and adolescents in the United Kingdom. The main objective of the study was to establish whether the parent-report Strengths and Difficulties Questionnaire (SDQ) was invariant across ethnicity and socioeconomic status groupings at six time points from 3 to 17 years (maximum N = 17,274). First, we fitted a series of confirmatory factor analysis models to the data and confirmed that the five-factor structure (emotional problems; peer problems; conduct problems; hyperactivity/inattention; and prosocial behaviour) had acceptable fit at ages 5, 7, 11, and 14 years. Next, we tested configural, metric, and scalar invariance at these time points and demonstrated scalar invariance across household income, parent highest education, and ethnicity categories. The five-factor structure did not fit well at ages 3 and 17 years; therefore invariance was not tested at these ages. These findings suggest the parent-report SDQ can be used to measure socioeconomic and ethnic inequalities in mental health from ages 5-14 years but more consideration is required outside these ages.