Abstract: 【Abstract】 Objective To evaluate the reliability and validity of the patient health questionnaire-9 （PHQ-9） in patients with acne. Methods A total of 300 patients with acne were enrolled from the Department of Dermatology, Affiliated Hospital of Southwestern Medical University from January 2017 to June 2018. Questionnaire survey was conducted among these patients to evaluate their depression status with the PHQ-9 and Hamilton depression scale （HAMD）, and the questionnaire completion time was recorded. The structured clinical interview（SCID） for American Diagnostic and Statistical Manual of Mental Disorders （4th Version） （DSM-Ⅳ） served as the "gold standard" for diagnosis of depression. Reliability analysis of the PHQ-9 was performed using the Cronbach′s α coefficient and one-week test-retest reliability. Factor analysis, Spearman correlation analysis and receiver operating characteristic （ROC） curve were used for validity analysis of the PHQ-9, and the screening validity was also analyzed in different subgroups. Results A total of 258 patients with acne completed all the survey, and 47 were diagnosed with depressive disorder according to the diagnostic gold standard SCID. An optimal cutoff score of 9 was determined for the diagnosis of depression using the PHQ-9, with a sensitivity of 95.7%, a specificity of 88.6%, and an area under the ROC curve （AUC） of 0.973 （95% CI: 0.956 - 0.990）. In different groups of people, the AUC ranged from 0.886 to 0.955. Validity analysis showed that the correlation coefficient between the total score of PHQ-9 and HAMD was 0.766, and the kappa value was 0.530. Factor analysis revealed that there were two common factors （cognitive-emotion factor and somatic symptom factor）, which explained 65.52% of the total variances. As reliability analysis showed, the Cronbach′s α coefficient of the PHQ-9 was 0.851, the correlation coefficients of the 9 items with the total scale score ranged from 0.550 to 0.709, the inter-item correlation coefficients ranged from 0.224 to 0.654, and the test-retest reliability value of the PHQ-9 was 0.824. The time to complete the PHQ-9 （4.9 ± 1.2 minutes） was significantly less than the time to complete HAMD （44.2 ± 5.9 minutes; t = 108.787, P < 0.001）. Conclusions The PHQ-9 shows good reliability and validity for the diagnosis of depression in patients with acne, and can be used for preliminary screening of depression in patients with acne. Compared with the HAMD, the PHQ-9 has obvious advantages of being more timesaving and manpower-saving to make it easier to implement in clinic.

Key words: Acne vulgaris, Depression, Questionnaires, Evaluation studies, Patient health questionnaire?9, Reliability, Validity