%0 Journal Article %T The Patient Health Questionnaire-9 among First-Trimester Pregnant Women in Japan: Factor Structure and Measurement and Structural Invariance between Nulliparas and Multiparas and across Perinatal Measurement Time Points %A Mikiyo Wakamatsu %A Mariko Minatani %A Ayako Hada %A Toshinori Kitamura %J Open Journal of Depression %P 121-137 %@ 2169-9674 %D 2021 %I Scientific Research Publishing %R 10.4236/ojd.2021.103008 %X Background: Depression is frequently seen among pregnant women. The PHQ-9 is a diagnostic criteria-based screening instrument. Objective: The objective is to identify the factor structure of the Patient Health Questionnaire-9 (PHQ-9) and to confirm its measurement and structural invariance regarding parity and observation time, as well as to examine reliability by calculating omega indices in a population of pregnant Japanese women. Methods: The PHQ-9 was distributed to 382 pregnant women with a gestational age of 10 to 13 weeks who were attending antenatal clinics. Of these women, 129 were tested again with the PHQ-9 one week later. Results: Exploratory factor analyses (EFAs) of the PHQ-9 items were conducted using a halved sample. Confirmatory factor analyses (CFAs) among the other halved sample compared the single-, two-factor models derived from the EFAs, literature model and bifactor model. The bifactor model was significantly better in terms of goodness-of-fit indices: ¦Ö²/df = 1.030 (18), CFI = 0.999, RMSEA = 0.012. ECV suggested multidimensionality. Internal consistency was excellent: ¦Ų = 0.868,