Psychiatric epidemiology is a field which seeks to study the conceptualization, etiology, and prevalence of mental illness in society. It is a subfield of the more general epidemiology. It is very difficult to accurately study mental illness conceptualization, etiology, and prevalence, and current techniques are relatively poor. Two areas of concern, sometimes called the crisis of psychiatric epidemiology today, are the high estimates of mental illness that many studies produce and the difference in results between studies.
How studies are conducted 
The common technique for psychiatric epidemiological research today is structured interviewing, a technique in which a series of questions is administered by lay interviewers to determine whether an individual is disordered or nondisordered.
Concerns of epidemiological research 
Clinical versus actual prevalence 
Clinical prevalence is a measure of how many people who seek out mental health services are actually diagnosed with a mental illness, whereas actual prevalence is the number of people in all of society who have a mental illness. It is much easier to study clinical prevalence because people with mental illness are identified by receiving a diagnosis, but epidemiologists are most interested in actual prevalence. To that end, efforts are continually made to improve research techniques in order to better estimate the actual prevalence of mental illness.
Sensitivity and specificity 
Another concern of psychiatric epidemiological studies are the issues of sensitivity and specificity. Sensitivity is a measure of how well a given selection criteria detects all of the people with a specific mental illness. Specificity is a measure of how well the technique identifies people with a mental illness without falsely identifying people without a mental illness.
Validity and reliability 
In order for a study to be useful, it must be both valid and reliable. Validity is a measure of how well the study measures what it is intended to measure. Reliability refers to how consistently the same result can be achieved. If an experiment is not reliable or valid, it will not withstand peer review.
Example: The Epidemiological Catchment Area Project 
In an attempt to measure the prevalence of mental illness in the United States, Lee Robins and Darrel A. Regier conducted a study called the Epidemiological Catchment Area Project which surveyed samples of the general population at five sites across America. In the study, it was found that about a third of all Americans suffer from mental illness at some point in their lives. This statistic is often referred to as lifetime prevalence.
Sociological concerns 
There is a negative consequence to the conduction of studies that are not valid and reliable. The medicalization of symptoms and character traits can have a damaging effect on those that display these symptoms and traits. For example, a person being surveyed for major depressive disorder in the ECA project would be asked questions such as "In your lifetime, have you ever had two weeks or more during which you felt sad, blue, depressed, or when you lost all interest and pleasure in things that you usually cared about?" Although many people would answer yes to this question, it is not necessarily because they were experiencing depression. Rather, they could be experiencing a natural reaction to some kind of life stress. Some speculate that by labeling this reaction as a mental illness, it increases the stigma of the person's symptoms and may create problems for their recovery. However, alternatively, by accurately assessing the high prevalence of mental disorders, stigma for having or ever having had such a disorder may decline.
Studies like the ECA may not accurately distinguish between psychiatric disorders and typical, non-pathological human stress responses.
See also 
- Horwitz, Allan V. and Teresa L. Scheid. A Handbook for the Study of Mental Health: Social Contexts, Theories, and Systems. New York: Cambridge University Press, 1999.
- Susser E, Schwartz S, Morabia A, Bromet EJ. "Psychiatric Epidemiology: Searching for the Causes of Mental Disorders." New York: Oxford University Press, 2006.