Batterham, PhilipSunderland, MatthewCarragher, NatachaCalear, Alison2021-02-082021-02-082056-4724http://hdl.handle.net/1885/222405Background There are few very brief measures that accurately identify multiple common mental disorders. Aims The aim of this study was to develop and assess the psychometric properties of a new composite measure to screen for five common mental disorders. Method Two cross-sectional psychometric surveys were used to develop (n = 3175) and validate (n = 3620) the new measure, the Rapid Measurement Toolkit-20 (RMT20) against diagnostic criteria. The RMT20 was tested against a DSM-5 clinical checklist for major depression, generalised anxiety disorder, panic disorder, social anxiety disorder and post-traumatic stress disorder, with comparison with two measures of general psychological distress: the Kessler-10 and Distress Questionnaire-5. Results The area under the curve for the RMT20 was significantly greater than for the distress measures, ranging from 0.86 to 0.92 across the five disorders. Sensitivity and specificity at prescribed cut-points were excellent, with sensitivity ranging from 0.85 to 0.93 and specificity ranging from 0.73 to 0.83 across the five disorders. Conclusions The RMT20 outperformed two established scales assessing general psychological distress, is free to use and has low respondent burden. The measure is well-suited to clinical screening, internet-based screening and large-scale epidemiological surveysThis research was supported by NHMRC Project Grant 1043952. P.J.B. and A.L.C. are supported by NHMRC Fellowships 1158707 and 1122544, respectivelyapplication/pdfen-AU© The Author(s) 2020. Published by Cambridge University Press on behalf of the Royal College of Psychiatristshttp://creativecommons.org/ licenses/by/4.0/Screeningassessmentdepressionanxiety202010.1192/bjo.2020.372023-10-22Creative Commons Attribution licence