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The use of well controls: an unhealthy practice in psychiatric research

  • S. Schwartz (a1) and E. Susser (a1) (a2)

Studies comparing cases with controls to uncover the causes of psychiatric disorders are common in biological research. The validity of these studies depends upon adherence to the methodological principles underlying the case-control design. However, these principles are often violated. One common practice that violates these principles is the use of well controls. In this paper we describe the bias that it can cause and discuss why the use of well controls leads to invalidity in case-control studies.


Using hypothetical numerical examples we illustrate the consequences of using well controls.


The results illustrate that the use of well controls can cause substantial bias. In no instance does the use of well controls improve validity.


We conclude that the use of well controls is an unhealthy practice in psychiatric research.

Corresponding author
*Address for correspondence: S. Schwartz, Ph.D., Mailman School of Public Health, Columbia University, 722 West 168th Street, Room 720b, New York, NY 10032, USA. (Email:
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This list contains references from the content that can be linked to their source. For a full set of references and notes please see the PDF or HTML where available.

WJ Lee , J Bindman , T Ford , N Glozier , P Moran , R Stewart , M Hotopf (2007). Bias in psychiatric case-control studies: literature survey. British Journal of Psychiatry 190, 204209.

D Schechter , R Levobitch (2005). Normal controls are expensive to find: methods to improve cost-effectiveness of the screening evaluation. Psychiatric Research 136, 6978.

E Susser , S Schwartz , A Morabia , EJ Bromet (2006). Psychiatric Epidemiology: Searching for the Causes of Mental Disorders. Oxford University Press: New York.

A Talati , SJ Fyer , MM Weissman (2008). A comparison between screened NIMH and clinically interviewed control samples on neuroticism and extraversion. Molecular Psychiatry 13, 122130.

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Psychological Medicine
  • ISSN: 0033-2917
  • EISSN: 1469-8978
  • URL: /core/journals/psychological-medicine
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