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Chapter 2: Burden of Mental and Behavioural Disorders: Previous page | 1,2,3,4,5,6,7,8

Prevalence of disorders

  Chapter 2

Mental disorders are not the exclusive preserve of any special group; they are truly universal. Mental and behavioural disorders are found in people of all regions, all countries and all societies. They are present in women and men at all stages of the life course. They are present among the rich and poor, and among people living in urban and rural areas. The notion that mental disorders are problems of industrialized and relatively richer parts of the world is simply wrong. The belief that rural communities, relatively unaffected by the fast pace of modern life, have no mental disorders is also incorrect.

Recent analyses done by WHO show that neuropsychiatric conditions which included a selection of these disorders had an aggregate point prevalence of about 10% for adults (GBD 2000). About 450 million people were estimated to be suffering from neuropsychiatric conditions. These conditions included unipolar depressive disorders, bipolar affective disorder, schizophrenia, epilepsy, alcohol and selected drug use disorders, Alzheimer's and other dementias, post traumatic stress disorder, obsessive and compulsive disorder, panic disorder, and primary insomnia.

The prevalence rates differ depending on whether they refer to people who have a condition at a point in time (point prevalence) or at any time during a period of time (period prevalence), or at any time in their lifetime (lifetime prevalence). Though point prevalence figures are often quoted, including in this report, one-year period prevalence figures are more useful for giving an indication of the number of people who may require services in a year. Prevalence figures also vary based on the concept and definitions of the disorders included in the study. When all the disorders included in ICD-10 (see Box 2.1) are considered, higher prevalence rates have been reported. Surveys conducted in developed as well as developing countries have shown that, during their entire lifetime, more than 25% of individuals develop one or more mental or behavioural disorders (Regier et al. 1988; Wells et al. 1989; Almeida-Filho et al. 1997).

Most studies have found the overall prevalence of mental disorders to be about the same among men and women. Whatever differences exist are accounted for by the differential distribution of disorders. The severe mental disorders are about equally common, with the exception of depression, which is more common among women, and substance use disorders, which are more common among men.

The relationship between poverty and mental disorders is discussed later in this chapter.

Disorders seen in primary health care settings

Mental and behavioural disorders are common among patients attending primary health care settings. An assessment of the extent and pattern of such disorders in these settings is useful because of the potential for identifying individuals with disorders and providing the needed care at that level.

Epidemiological studies in primary care settings have been based on identification of mental disorders by the use of screening instruments, or clinical diagnosis by primary care professionals or by psychiatric diagnostic interview. The cross-cultural study conducted by WHO at 14 sites (Üstün & Sartorius 1995; Goldberg & Lecrubier 1995) used three different methods of diagnosis: a short screening instrument, a detailed structured interview, and a clinical diagnosis by the primary care physician. Though the prevalence of mental disorders across the sites varied considerably, the results clearly demonstrate that a substantial proportion (about 24%) of all patients in these settings had a mental disorder (see Table 2.1 ). The most common diagnoses in primary care settings are depression, anxiety and substance abuse disorders. These disorders are present either alone or in addition to one or more physical disorders. There are no consistent differences in prevalence between developed and developing countries.

Table 2.1 Prevalence of major psychiatric disorders in primary health care

  Current depression Generalized anxiety Alcohol dependence All mental disorders (according to CIDIa)
Cities (%) (%) (%) (%)
Ankara, Turkey 11.6 0.9 1 16.4
Athens, Greece 6.4 14.9 1 19.2
Bangalore, India 9.1 8.5 1.4 22.4
Berlin, Germany 6.1 9 5.3 18.3
Groningen, Netherlands 15.9 6.4 3.4 23.9
Ibadan, Nigeria 4.2 2.9 0.4 9.5
Mainz, Germany 11.2 7.9 7.2 23.6
Manchester, UK 16.9 7.1 2.2 24.8
Nagasaki, Japan 2.6 5 3.7 9.4
Paris, France 13.7 11.9 4.3 26.3
Rio de Janeiro, Brazil 15.8 22.6 4.1 35.5
Santiago, Chile 29.5 18.7 2.5 52.5
Seattle, USA 6.3 2.1 1.5 11.9
Shanghai, China 4 1.9 1.1 7.3
Verona, Italy 4.7 3.7 0.5 9.8
Total 10.4 7.9 2.7 24
aCIDI: Composite International Diagnostic Interview.
Source: Goldberg DP, Lecrubier Y (1995). Form and frequency of mental disorders across centres. In: Üstün TB, Sartorius N, eds. Mental illness in general health care: an international study. Chichester, John Wiley & Sons on behalf of WHO: 323-334.

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