Special Theme – Mental Health Psychiatric …

1 Psychiatric epidemiology : selected recentadvances and future directionsRonald C. Kessler1 Reviewed in this article are selected recent advances and future challenges for Psychiatric epidemiology . Majoradvances in descriptive Psychiatric epidemiology in recent years include the development of reliable and valid fullystructured diagnostic interviews, the implementation of parallel cross-national surveys of the prevalences andcorrelates of Mental disorders, and the initiation of research in clinical epidemiology . Remaining challenges include therefinement of diagnostic categories and criteria, recognition and evaluation of systematic underreporting bias insurveys of Mental disorders, creation and use of accurate assessment tools for studying disorders of children,adolescents, the elderly, and people in less developed countries, and setting up systems to carry out small areaestimations for needs assessment and programme planning.

2 Advances in analytical and experimental epidemiologyhave been more modest. A major challenge is for Psychiatric epidemiologists to increase the relevance of theiranalytical research to their colleagues in preventative psychiatry as well as to social policy analysts. Another challengeis to develop interventions aimed at increasing the proportion of people with Mental disorders who receive encouraging advances, much work still needs to be conducted before Psychiatric epidemiology canrealize its potential to improve the Mental Health of :psychiatry; epidemiology , trends; Mental disorders, epidemiology ; psychopathology; review page 471 le re sume en franc ais.

3 En la pa gina 472 figura un resumen en espan is concerned with understanding andcontrolling disease epidemics by investigating em-pirically the associations between variation inexposure to disease-causing agents external to theindividual, variation in the resistance of individualsexposed to the disease-causing agents, and variationin resistance resources in the environments ofexposed individuals (1). These investigations areinitially carried out by examining natural based on these analyses are then, usually,tested provisionally in naturalistic quasi-experimentalsituations with matching or statistical controls used toapproximate the conditions of an experiment.

4 If thehypotheses stand up to these preliminary tests, theyare evaluated in interventions aimed at preventing theonset or altering the course of the epidemiology traditionally lagsbehind other branches of epidemiology because ofdifficulties encountered in conceptualizing andmeasuring Mental disorders. As a result, muchcontemporary Psychiatric epidemiology continuesto be descriptive, focusing on the estimation ofdisorder prevalences and subtypes (2) at a time whenother branches of epidemiology are making progressin documenting risk factors and developing pre-ventive interventions (3). To the extent thatpsychiatric epidemiologists study risk, they tend tofocus on broad nonspecific risk markers, such asgender and social class, rather than on modifiable riskfactors, hence limiting the possibilities for interven-tion.

5 However, this situation is changing as descrip-tive issues are being resolved, more analyticalquestions are being addressed, and preventiveinterventions are being Psychiatric epidemiologyAdult community epidemiological surveysDescriptive Psychiatric epidemiology has gonethrough an unprecedented period of growth overthe past twenty years. Starting with the Epidemiolo-gic Catchment Area (ECA) study in the USA (2), largesurveys of adult Mental disorders in the generalpopulation have been carried out in numerouscountries throughout the world. An importantinnovation of the ECA was the use of a fullystructured research diagnostic interview known asthe Diagnostic Interview Schedule (DIS,4).

6 Method-ological studies demonstrated that the DIS yieldsreliable and valid diagnoses (5), a result that was veryimportant in promoting the ECA DIS methodologyin subsequent general population first expansion of the ECA DIS metho-dology was carried out by WHO in collaboration withthe US Alcohol, Drug, and Mental Health Admin-istration to include International Statistical Classifica-tion of Diseases (ICD) criteria for research and toproduce versions of the instrument in many different1 Correspondence should be addressed to Dr Kessler, Departmentof Health Care Policy, Harvard Medical School, 180 Longwood Avenue,Boston, MA, USA (email: Theme Mental Health464#World Health Organization 2000 Bulletin of the World Health Organization, 2000,78(4)languages.)

7 The resulting instrument, the CompositeInternational Diagnostic Interview (CIDI,6), firstbecame available in 1990. WHO technical supportled to an unprecedented number of major epidemio-logic surveys using the CIDI in countries as diverse asBrazil (7), Canada (8), Germany (9), Mexico (10), theNetherlands (11), and Turkey (12).In 1997, WHO created the InternationalConsortium in Psychiatric epidemiology (ICPE) tocoordinate the comparative analysis of these data(13). ICPE also provides technical assistance toresearchers planning new CIDI surveys. The WHOW orld Mental Health 2000 (WMH2000) initiative hasgrown out of these technical assistance will coordinate general population CIDI surveys in 20 countries in the year 2000, distributedglobally in North America (Canada, USA), LatinAmerica (Brazil, Colombia, Mexico, Peru), Europe(Belgium, France, Germany, Italy, the Netherlands,Spain, the Ukraine), the Middle East (Israel), Africa(South Africa), Asia (China, India, Japan) and thePacific (Indonesia, New Zealand).

8 Several important results have consistentlyemerged from the DIS and CIDI disorders are among the most prevalentclasses of chronic diseases in the general popula-tion, with lifetime-to-date prevalences often closeto 50% of the population and with 12-monthprevalences typically in the 15 25% range (2).. Mental disorders typically have much earlier agesof onset than other chronic diseases. Anxietydisorders have median ages of onset in the early tolate teens in most of these surveys, while moodand substance use disorders have median ages ofonset in the early to mid twenties (14).. Mental disorders are among the most impairing ofall chronic diseases (15).

9 Respondents with the most severe and disablingmental disorders in these surveys usually meetlifetime criteria for a number of different ICD andDiagnostic and Statistical Manual of MentalDisorders (DSM) syndromes (16)..Only a minority of the respondents in thesesurveys who meet criteria for a Mental disorderreport that they received treatment in thepreceding year (17). The measures of disorderseverity included in the surveys are consistentlyassociated with probability of service use, like-lihood that service use occurs in the specialtysector, and intensity of treatment, documentingthat there is some rationality both in help-seekingand in the allocation of treatment , the surveys also show that only aminority of patients describe a course of therapythat is even minimally adequate in terms ofcurrently available treatment guidelines (18).

10 The high rates of disorder found in these surveyshave led some commentators to raise questionsabout the plausibility of the prevalence estimates (19).As clinical reappraisal studies clearly show that theprevalence estimates in CIDI surveys are not higherthan those obtained in blind clinician reinterviews(20), concerns about the high prevalence estimateshave focused largely on the underlying validity of theICD and DSM systems. Clinical significance criteriawere added to nearly half the diagnoses in the DSM-IV system in response to these concerns to addressthe perceived problem that the previous diagnosticcriteria led to overdiagnosis of disorder amongpeople whose symptoms were clinically , this has led to even more controversyregarding whether the inclusion of these new criteriais legitimate (21).