The psychometric properties of PHQ-4 anxiety and depression screening scale among out of school adolescent girls and young women in Tanzania: a cross-sectional study

Background Literature suggests that most mental disorders have their onset in childhood and adolescence, but go undiagnosed until adulthood. Shorter versions of the screening tools such as the Patient Health Questionnaire with four items (PHQ-4) may help to improve screening coverage. This study assessed the psychometric properties of the PHQ-4 in screening for core symptoms of depression and anxiety among out of school adolescent girls and young women (AGYW). Methods This is a cross-sectional analysis of data from a cluster randomized controlled trial conducted among AGYW between June and July 2018 in North-West Tanzania. Two thousand four hundred twenty-six out-of-school AGYW aged 15 to 23 years were included. Data were collected on tablets using audio computer-assisted self-interviews (ACASI). Cronbach’s α was used to measure the reliability of the PHQ-4 while confirmatory factor analysis (CFA) and principal components analysis (PCA) were used for construct validity assessment. In CFA, three criteria were used to assess how well the model fits the data: Standardized Root Mean Square Residual (SRMR), the Comparative Fit Index (CFI), the Root Mean Square Error of Approximation (RMSEA) and 90% confidence interval for RMSEA. Results Of the 2426 participants, 33.8 and 35.5% screened positive for core symptoms of anxiety (GAD-2 ≥ 3) and depression (PHQ-2 ≥ 3), respectively. Cronbach’s α of the PHQ-4 was 0.81. Both items-correlation and corrected items-correlation of the PHQ-4 had total correlations above 0.5 ( p < 0.01). CFA showed that all items loaded significantly onto the single factor, and loadings were strong, ranging from 0.67 to 0.77 ( p < 0.01). CFA indicates that the PHQ-4 scale stand for a unidimensional construct with good model fit (CFI = 0.995, SRMR = 0.013, RMSEA = 0.054 and 90% CI for RMSEA (0.031–0.079)). PCA confirmed two distinct components; GAD-2 (anxiety) and PHQ-2 (depression). Those who reported having suicidal thoughts and social function problems had significantly higher scores on PHQ-2, GAD-2, and PHQ-4 screening items ( p < 0.01). Conclusions The findings suggest that the PHQ-4 scale can reliably and validly screen for core symptoms of depression and anxiety among out of school AGYW. This tool is short and easy to administer. Thus, the PHQ-4 scale can be very useful in screening for anxiety and depression symptoms in the community, primary health facilities, research and programmatic settings.