Measurement invariances of the PHQ-9 across gender and age groups in Chinese adolescents

Introduction The nine-item Patient Health Questionnaire (PHQ-9) is widely used to determine the severity of depression in adult populations, but its psychometric properties with regard to adolescents has been poorly explored. The present study aims to identify the factor structure and examine the measurement invariance of this instrument across genders and age groups in a Chinese adolescent sample. Methods A large sample of Chinese schoolchildren completed the PHQ-9 in a cross-sectional survey in Hong Kong (N = 10 933). A confirmatory factor analysis (CFA) to test the factor structure and a multiple group CFA to test the gender and age invariances of the PHQ-9 in adolescents were conducted. Cronbach alpha was used to assess the reliability of the questionnaire, and Pearson correlations with anxiety, self-esteem, and perceived control were used to assess its construct validity. Results The CFA results indicate that a one-factor model with three pairs of item correlations fitted the PHQ-9 data well, and measurement invariances by age and gender were supported. The PHQ-9 also possesses adequate internal consistency (>.84) and is strongly correlated with anxiety (>.77), self-esteem (<-.57), and perceived control (<-.56) in the expected directions in the overall sample and in the gender and age subsamples. Discussion The results support the claim that the PHQ-9 is a reliable and valid scale and can be used to assess and compare depressive severity across ages and genders during the period of adolescence.