Categories in epidemiology

Idea: Collecting and analyzing data requires categories: Have we omitted relevant categories or mixed different phenomena under one label? What basis do we have for subdividing a continuum into categories? How do we ensure correct diagnosis and assignment to categories? What meaning do we intend to give to data collected in our categories?

1. We can identify a chain of steps in scientific inquiry in which each step involves assumptions and is open for negotiation and wider influences (Taylor 2005, chapter 2).

All possible phenomena

  • (-> experimental manipulation)
    • -> phenomenon deemed interesting
      • -> questions asked
        • -> categories demarcated
          • -> observations made
            • -> data collected
              • -> patterns perceived
                • -> predictions made
                  • and/or hypotheses about causes
                    • -> actions supported

Decisions made at early steps influence outcomes at later steps. E.g., if schizophrenia is used as a category as defined by the DSM, it is harder for a clinician to pay attention to the contextual and life history information of patients (Poland 2004). This is not a one-way sequence. There is also the possibility that desired outcomes for the later stages (especially the actions the researcher favors in advance and would like to be supported by the inquiry) influence decisions made at earlier steps (as indicated in the following schema).

2. When reading a study, take note of:

  • a) where the categories demarcated seem to favor certain kinds of action over others (e.g., Galton only collected data about similarities among relatives so there was no way he could explore hypotheses about non-hereditary or environmental influences or illuminate action regarding those influences); and
  • b) what kinds of remedies you would propose whenever the categories seem limited (e.g., disaggregate the category “approve of Congress,” which includes Democrats who want the Democratic majority in the Senate not to accede to fillibustering Republicans and Republicans who don’t want Democrats to get their way).

Hymowitz (2007) [not a scholarly article] disaggregates divorce rates in the USA, which hide different phenomena and trends in different social classes.

Pickles and Angold (2003) review the debate about whether categories of psychopathology are best thought of as categorical (e.g., one has schizophrenia or doesn’t) or dimensional (e.g., there are degrees of schizophrenic behavior).

Poland (picking up on both points above) argues that the category “of schizophrenia and the associated received view [does not] have anything useful to add to clinical practice concerned with severe mental illness.”

George Brown (UK) and Bruce Dohrenwend (USA) have done research for decades on the relationship between mental illness and life events or difficulties. Brown (as described by Birley and Goldberg 2000) developed methods that tried to expose the meaning of an event for the person and was critical of the US emphasis on “objective” surveys (where the same event, e.g, death of a spouse, might have very different meanings and significance for the subject). Dohrenwend describes his group’s eventual realization of this issue, but they still wanted to measure events without having the context fused into the rating of the event.

Davey-Smith et al. (2000) consider comparative methods for studying socioeconomic position and health in different ethnic communities, e.g.,  — Does socio-economic status (SES) mean the same thing for different communities? If not, what is our proposed remedy?

(This post continues a series laying out a sequence of basic ideas in thinking like epidemiologists, especially epidemiologists who pay attention to possible social influences on the development and unequal distribution of diseases and behaviors in populations [see first post in series].)


Birley, J. and D. Goldberg (2000). George Brown’s contribution to psychiatry: The effort after meaning. Where Inner and Outer Worlds Meet. T. Harris. London, Routledge: 55-60.

Brown, G. W. and T. O. Harris (1978). Sociology and the aetiology of depression; Depression and Loss; A Model of Depression; Summary and conclusions. Social Origins of Depression: a Study of Psychiatric Disorder in Women. New York, Free Press: 3-20; 233-293.

Davey-Smith, G. et al. (2000). Ethnicity, health and the meaning of socio-economic position Pp. 25-37 In Graham, H., Ed. Understanding health inequalities. Buckingham [England], Open University Press.

Dohrenwend, B. P., K. G. Raphael, et al. (1993). The structured event probe and narrative rating method for measuring stressful life events. Handbook of Stress: Theoretical and Clinical Aspects. L. Goldberg and S. Breznitz. New York, Free Press: 174-199.

Hymowitz, K. S. (2007). “Marriage and Caste in America: Separate and Unequal Families in a PostMarital Age.” Heritage Lecture #1005.

Pickles, A. and A. Angold (2003). “Natural categories or fundamental dimensions: On carving nature at the joints and the rearticulation of psychopathology.” Development and Psychopathology 15: 529-551.

Poland, J. (2004). “Bias and schizophrenia.” Pp. 149-161 in P. J. Caplan and L. Cosgrove, eds. Bias in Psychiatric Diagnosis. Lanham, MD: Rowman & Littlefield.

Taylor, P. J. (2005). Unruly Complexity: Ecology, Interpretation, Engagement. Chicago, University of Chicago Press.


One thought on “Categories in epidemiology

  1. Pingback: Problems with categories and possible responses « Intersecting Processes

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