1 The Measurement of Mental Disorder Why is it so difficult to determine who is mentally disordered when interviewing people in the community?

2 Why do community sampling?  Helpful in formulating mental health policy  Helpful in evaluating theories of causation  Helpful in planning delivery of mental health services  Helpful in justifying requests for funding to support research and service provision

3 2 Major Epidemiologic Studies  Epidemiologic Catchment Area (ECA) Project Robins & Regier, 1991 Surveyed samples of general population in 5 sites—New Haven, CT to Los Angeles, CA  National Comorbidity Survey (NCS) Kessler et al., 1994 Focused on degree to which different disorders appeared in same individual

4 Difficulties Encountered  Prevalence rates of mental disorders seem to be too high ECA found that 1/3 of Americans suffer from a mental disorder at one point in their lives NCS figure was 1/2  Although the studies used similar instruments, the results were quite different in many areas ECA estimated that 6% of Americans suffer from a depressive disorder at some point in their lives NCS estimated 17%

5 Clinical prevalence vs. true prevalence  Why not just count the number of people in clinical settings?  Clinical prevalence of mental disorder is not a measure of true prevalence Clinical prevalence is a measure of how many people seek and receive treatment; true prevalence is a measure of how many people have mental disorders, whether or not they seek or receive treatment  It’s the rate of untreated mental disorder that is important for planning purposes.

6 What does socioeconomic status (SES) have to do with mental disorder?  Diverse mix of services may not be accessible, especially in lower-class communities In lower class communities, there are fewer office therapists available (poor people can’t afford them) Poor people more likely to use public hospitals; middle and upper- class people more likely to use office therapists  Social class, ethnicity, and gender have an effect on how mental disorders are expressed, diagnosed, and handled  Lower SES people may be under more chronic stress, may be more prone to develop mental disorders

7 Conceptual validity  Measurement tool has conceptual validity when it is successful in distinguishing between persons who have a mental disorder and those who don’t  Too expensive to have clinicians interviewing large community samples, so questionnaires are used. It is very difficult to create a questionnaire that has conceptual validity.

8 Back to the DSM  Basic idea is that disorders can be recognized by symptoms  DSM gives rules for deciding, from symptoms, which disorder a person has, if any  DSM is theory-neutral  DSM is useful tool for psychiatric epidemiologists

9 Fundamental question  What is mental disorder, and how does it differ from the “normal suffering of everyday life” of “problems in living”?  According to DSM, pattern of symptoms that is identified must be associated with distress, disability, dysfunction. Dysfunction must be harmful. Disturbance must not be only a conflict between an individual and society.

10 Validity  Criteria for classifying a disorder must be: Sensitive: when applied the criteria should not indicate that someone is normal when, in fact, they have a disorder (false negative) Specific: when applied the criteria should not indicate that someone has a disorder when they are normal (false positive)

11 More on validity  False positives more of a problem than false negatives—because the normal population is much larger than the disordered population.  If there are many false positives, the estimated prevalence of a disorder can be very much overestimated.

12 Problem with using DSM criteria in epidemiology  DSM is designed to be used in a clinical setting, where clinicians have the luxury of refining the diagnosis after several interviews.  Questionnaires used in community surveys give epidemiologist a quick diagnosis, one that cannot be refined later.

13 Problems with epidemiological studies of mental disorders  No matter how carefully the instrument for measurement is developed, sample is selected, and data is collected, if the definitions of mental disorders do not give a clear picture of the disorders, then the studies will be flawed.  Question: How else could we estimate the prevalence of mental disorders?