1 Lady Davis Institute for Medical Research, Jewish General Hospital, Montréal, Québec, Canada.
2 Department of Psychiatry, McGill University, Montréal, Québec, Canada.
3 Department of Epidemiology, Biostatistics and Occupational Health, McGill University, Montréal, Québec, Canada.
4 Department of Psychology, McGill University, Montréal, Québec, Canada.
5 Schulich Library of Physical Sciences, Life Sciences, and Engineering, McGill University, Montreal, Quebec, Canada.
6 Department of Clinical, Neuro and Developmental Psychology, Amsterdam Public Health Research Institute, Vrije Universiteit, Amsterdam, the Netherlands.
7 Hull York Medical School and the Department of Health Sciences, University of York, Heslington, York, UK.
8 Department of Medicine, Department of Health Research and Policy, Department of Biomedical Data Science, Department of Statistics, Stanford University, Stanford, California, USA.
9 Library, Concordia University, Montréal, Québec, Canada.
10 Department of Community Health Sciences, University of Calgary, Calgary, Alberta, Canada.
11 Hotchkiss Brain Institute and O'Brien Institute for Public Health, University of Calgary, Calgary, Alberta, Canada.
12 Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
13 Department of Psychiatry, Makerere University College of Health Sciences, Kampala, Uganda.
14 Department of General Practice and Primary Health Care, University of Auckland, Auckland, New Zealand.
15 Louis and Gabi Weisfeld School of Social Work, Bar Ilan University, Ramat Gan, Israel.
16 Endocrine Research Center, Institute of Endocrinology and Metabolism, Iran University of Medical Sciences, Tehran, Iran.
17 Ageing Clinical & Experimental Research Team, Institute of Applied Health Sciences, School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Aberdeen, Scotland, UK.
18 Department of Medicine, McGill University, Montréal, Québec, Canada.
19 Department of Rehabilitation Medicine, University of Washington, Seattle, Washington, USA.
20 Centre for Research on Ageing, Health and Wellbeing, Research School of Population Health, The Australian National University, Canberra, Australia.
21 Melbourne Institute of Applied Economic and Social Research, University of Melbourne, Melbourne, Australia.
22 Centre for Brain and Mental Health Research, University of Newcastle, New South Wales, Australia.
23 Department of Neurosciences and Behavior, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil.
24 Department of Medicine and Therapeutics, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong Special Administrative Region (SAR), China.
25 Asia Diabetes Foundation, Prince of Wales Hospital, Hong Kong SAR, China.
26 Hong Kong Institute of Diabetes and Obesity, Hong Kong SAR, China.
27 Department of Pediatrics, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, North Carolina, USA.
28 Department of Psychiatry, University of Rochester Medical Center, New York, USA.
29 Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, the Netherlands.
30 Department of Psychiatry and Behavioral Sciences, University of Washington, Seattle, Washington, USA.
31 Department of Psychosomatic Medicine, Center fo

Background: Item 9 of the Patient Health Questionnaire-9 (PHQ-9) queries about thoughts of death and self-harm, but not suicidality. Although it is sometimes used to assess suicide risk, most positive responses are not associated with suicidality. The PHQ-8, which omits Item 9, is thus increasingly used in research. We assessed equivalency of total score correlations and the diagnostic accuracy to detect major depression of the PHQ-8 and PHQ-9.

Methods: We conducted an individual patient data meta-analysis. We fit bivariate random-effects models to assess diagnostic accuracy.

Results: 16 742 participants (2097 major depression cases) from 54 studies were included. The correlation between PHQ-8 and PHQ-9 scores was 0.996 (95% confidence interval 0.996 to 0.996). The standard cutoff score of 10 for the PHQ-9 maximized sensitivity + specificity for the PHQ-8 among studies that used a semi-structured diagnostic interview reference standard (N = 27). At cutoff 10, the PHQ-8 was less sensitive by 0.02 (-0.06 to 0.00) and more specific by 0.01 (0.00 to 0.01) among those studies (N = 27), with similar results for studies that used other types of interviews (N = 27). For all 54 primary studies combined, across all cutoffs, the PHQ-8 was less sensitive than the PHQ-9 by 0.00 to 0.05 (0.03 at cutoff 10), and specificity was within 0.01 for all cutoffs (0.00 to 0.01).

Conclusions: PHQ-8 and PHQ-9 total scores were similar. Sensitivity may be minimally reduced with the PHQ-8, but specificity is similar.