Measuring Depression and Anxiety with 4 items? Adaptation of the PHQ-4 to increase its Sensitivity to Subclinical Variability

The PHQ-4 is an ultra-brief (4 items) screening questionnaire for depression and anxiety. In thisbrief report, we test the benefits of adding one additional response option (“Once or twice”, inbetween “Not at all” and “Several days”) to improve the scale’s sensitivity to milder alterations,and thus increase its usefulness in subclinical populations. In study 1 (N=485), we provideevidence using Item Response Theory (IRT) that the new response option does improve thescale’s psychometric quality and extends the sensitivity to the measured constructs on the lowerend of the spectrum. In study 2 (N=836), we show that the refined version offers an improvedsensitivity to subclinical variability in depression (indexed by the BDI-II) as compared to theoriginal version. In conclusion, adding the “once or twice” response option is a low-cost no-downsides way of increasing the PHQ-4’s sensitivity to subclinical variability, making it a toolof choice for general population research.