Psychometric Properties and Validity of a Mobile Patient Health Questionnaire-9 (MPHQ-9) for Ecological Momentary Assessment in Depressed Adults

Ecological momentary assessment (EMA) offers advantages over retrospective questionnaires by reducing recall bias and capturing rapid symptom dynamics, and it is increasingly used to measure depression symptoms. However, few depression symptom measures are validated for EMA use in the manner expected for traditional questionnaires. Therefore, the current study examined the internal consistency, longitudinal stability, and convergent validity of the Mobile Patient Health Questionnaire-9 (MPHQ-9), a version of the PHQ-9 modified for EMA. Depressed participants (N = 280; Female = 83.93%; White = 79.29%) completed the MPHQ-9 three times daily for 90 days. Data from the first and last 2 weeks were analyzed to align with a pre-study PHQ-9 and post-study PHQ-9 and Inventory of Depression and Anxiety Symptoms - Expanded Version (IDAS-II). The MPHQ-9 demonstrated fair to substantial adjusted item-total correlations (r = 0.42–0.83), often exceeding the PHQ-9 (r = 0.39–0.72), with Cronbach’s alpha coefficients of .91 and .81, respectively. Reliability analyses of the MPHQ-9 using generalizability theory (GT) and multilevel modeling (MLM) to account for repeated measures yielded substantial between-person reliability (~1.0) but mixed within-person reliability estimates of 0.81 (GT) and 0.44 (MLM). The MPHQ-9 showed moderate stability (r = .69, ICC = .58), compared to the slight stability of the PHQ-9 (r = .39, ICC = .37). There was moderate agreement between the MPHQ-9 and both the PHQ-9 (r = .71) and the IDAS-II General Depression subscale (r = .65). This study provides initial validation of the MPHQ-9 and compares its psychometric properties to the traditional PHQ-9.