An Item-Level Analysis of Patient Health Questionnaire (PHQ-9) Among Adolescents in Primary Care.

Objective: Adolescents are at increased risk for meeting diagnostic criteria for depression and chronic impairments in functioning. Despite the potential consequences, adolescents have poor access to mental health treatment. To increase access, professional organizations recommend pediatricians regularly screen for symptoms of depression with the goal of identifying, preventing, and treating depression. The Patient Health Questionnaire (PHQ-9) has become a frequently used screener in primary care due to its brevity and well-established psychometric properties among both adults and adolescents. The present study aims to expand on this research by examining the quality of individual PHQ-9 items in an ecologically valid sample of adolescents screened for depression during their well-child exams. Method: Participants include 11,058 adolescents who were screened using the PHQ-9 at a primary care clinic. Results: This retrospective chart review study demonstrated that all nine items discriminate moderate to severe depression severity. The PHQ-9 provides the most information about two standard deviations above the mean, indicating more error when measuring mild levels of depression. Some PHQ-9 items function best at lower levels of depression, whereas others function best at higher levels of depression. Four of the PHQ-9 items do not show evidence of equal interval response options. Conclusions: Individual symptoms of depression endorsed by adolescents should be considered when interpreting the overall depression scores. The clinical implications related to ultra-brief depression screening and suicidal ideation screening are discussed as well as limitations and future directions.