The Patient Health Questionnaire-9 for measuring depressive symptoms among the general population in Hong Kong

Objectives: The Patient Health Questionnaire-9 (PHQ-9) assesses depressive symptoms by self-report, is brief, and was developed to correspond to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, criteria for major depression. This article presents information regarding its reliability and validity and the distribution of scores in a Chinese community sample in Hong Kong.

Methods: A total of 6028 participants 15 years or older were recruited using random household sampling. They completed the Chinese version of the PHQ-9, the Happiness Scale, the Chinese Health Questionnaire, and the Short-Form 12-Item Health Survey (SF-12). Information was also gathered on health and health service use.

Results: Exploratory factor analysis and confirmatory factor analysis supported a single factor with strong loadings for all 9 items. Multiple-group analyses demonstrated that the structure can be generalized across sex and age groups (ie, adolescents, adults, and individuals 65 years or older). The internal consistency of the PHQ-9 was 0.82. The test-retest reliability over a 2-week interval was 0.76. As expected, the total score of the PHQ-9 was significantly associated with the Chinese Health Questionnaire (r = 0.49) and the Happiness Scale (r = -0.41). In addition, as expected, the relationship with the physical component subscale of the SF-12 was significantly weaker (r = -0.27) than for the mental component subscale of the SF-12 (r = -0.60). Participants with higher scores on the PHQ-9 were more likely to report having been diagnosed with depression by a physician, having chronic illness, using medicine, and using inpatient and outpatient health services. Almost 40% of participants did not report any depressive symptoms (score, 0). Self-reported symptoms at a level that would qualify for a diagnosis of major depressive disorder were provided by 1.7% of the participants.

Conclusions: Our data support the reliability and validity of the PHQ-9 in assessing depressive symptoms among the general population in Hong Kong. Its validity against diagnostic interview for major depressive disorder and its sensitivity and specificity should be determined in future studies.