In this manuscript, we present the findings from our prospective diagnostic concordance study, which aimed to evaluate the validity and feasibility of a smartphone-based mood-tracking application compared to the standard PHQ-9 questionnaire. The study involved 60 participants, including individuals with Major Depressive Disorder and healthy controls, highlighting the utility of real-time mood monitoring in clinical practice. Key findings from our study include: Strong concordance between …

BACKGROUND Depression is highly prevalent globally and significantly contributes to disability. Traditional assessments often suffer from recall bias, and real-time symptom tracking through digital tools may offer substantial advantages. OBJECTIVE This study aims to examine the validity and feasibility of a smartphone-based mood-tracking application in comparison with the Patient Health Questionnaire-9 (PHQ-9), and to explore the relationship between sleep duration and mood states. METHODS This prospective diagnostic concordance study involved 60 participants (36 with DSM-IV-diagnosed Major Depressive Disorder [MDD] and 24 controls), aged 18-60, recruited from Rajavithi Hospital, Bangkok. Participants utilized the mobile app daily over four weeks, recording mood scores (1-10), sleep duration, and optional narrative entries. PHQ-9 assessments were conducted at baseline, day 14, and day 28. Statistical analyses included Pearson correlation, multiple linear regression, and repeated-measures ANOVA. RESULTS Participants were predominantly female (76.7%) with a mean age of 32.8 years. Daily mood scores showed a non-significant improvement trend (p = 0.54), while PHQ-9 scores declined significantly (p = 0.001). Mood ratings correlated with PHQ-9 scores (β = -1.93, 95% CI [-2.69, -1.18]; p<0.001). Within the MDD subgroup, the correlation was β = -1.41 (95% CI [-2.37, -0.44]; p=0.006). Sleep duration was associated with PHQ-9 scores only among the controls (β = -2.18, 95% CI [-4.29, -0.07]; p = 0.043). Overall app satisfaction averaged 4.32/5. CONCLUSIONS Participants were predominantly female (76.7%) with a mean age of 32.8 years. Daily mood scores showed a non-significant improvement trend (p = 0.54), while PHQ-9 scores declined significantly (p = 0.001). Mood ratings correlated with PHQ-9 scores (β = -1.93, 95% CI [-2.69, -1.18]; p<0.001). Within the MDD subgroup, the correlation was β = -1.41 (95% CI [-2.37, -0.44]; p=0.006). Sleep duration was associated with PHQ-9 scores only among the controls (β = -2.18, 95% CI [-4.29, -0.07]; p = 0.043). Overall app satisfaction averaged 4.32/5.