Concerns have been raised that PHQ-9 instructions (“bothered by” symptoms) conflict with frequency-based response options, potentially leading to some patients experiencing difficulty mapping lived experience onto response options and may conflate frequency with burden. We tested whether weekly PHQ scores aligned more with symptom frequency or burden using an intensive longitudinal design. Depressed patients ( n = 23) reported daily symptom presence and burden ( n = 1652 days) and completed weekly PHQ-9 ( n = 236 weeks). Mixed-effects models decomposed within- and between-person effects and estimated patient-specific frequency–burden weights. Frequency and burden were highly correlated; each predicted PHQ-9 scores when modeled alone, but neither showed unique effects jointly. Thus, weekly PHQ-9 change mainly reflected a shared symptom-severity signal; person-level heterogeneity was suggested but uncertain. Findings are preliminary and should be interpreted alongside the PHQ-9's strong evidence base. • Weekly PHQ-9 scores tracked both daily symptom frequency and perceived burden. • Within-person rises in frequency or burden predicted higher PHQ-9 in separate models. • Patients varied in whether PHQ-9 reflected rather frequency vs burden.
Seizer et al. (Wed,) studied this question.