Screening for anxiety and depression: Validation of the PHQ-4 in a large sample of rehabilitation patients

BackgroundAnxiety and depression are the most prevalent mental disorders in both general and rehabilitation populations. The Patient Health Questionnaire for Depression and Anxiety (PHQ-4) is an ultra brief screening instrument previously validated for use in general and primary care populations. We aimed to validate the PHQ-4 for the rehabilitation setting by establishing its factorial and convergent validity. The availability of such screenings for rehabilitation is critical, as psychological distress is an important contributor to rehabilitation outcomes. MethodsThe study sample consisted of 66,412 rehabilitation patients from 15 inpatient rehabilitation centers in Austria, covering rehabilitation of various (non-psychiatric) medical indications. To validate the PHQ-4s factorial validity, we conducted confirmatory factor analyses (CFA) comparing one-factor (psychological distress) or two-factor (anxiety and depression) models. Multi-group CFAs assessed measurement invariance across age, gender, and medical indication. Convergent validity was tested using ordinal logistic regression to model the PHQ-4s association with measures of quality of life, vocational impairment, and work ability. We conducted additional analyses to rule out spurious results based on the very large same size used. ResultsThe results demonstrated an overall excellent fit for the two-factor solution, outperforming the one-factor solution. Reliability indices for the two-factor solution were adequate for a screening instrument. Measurement invariance was demonstrated across age, gender, and all but one tested medical indications. Ordinal logistic regression supported convergent validity, showing associations with age and common patient reported outcomes. ConclusionsThis study demonstrates that the PHQ-4 is a valid and reliable tool for screening for anxiety and depression in rehabilitation settings. Based on a substantial sample and preregistered analysis strategy, the findings will likely generalize to rehabilitation populations in other countries. Trial RegistrationThe current study was approved by the Ethics Committee of the Medical University of Vienna ([MASKED FOR REVIEW: reference number]) and preregistered on the Open Science Framework ([MASKED LINK FOR REVIEW: https://osf.io/79fgb/?view_only=de7954e85040422db0db08d24ac7ed79]).