Prevalence and statistics of depression around the world

In recent years, depression has been considered one of the main causes of decline and loss of working capacity worldwide. In terms of the share of years lost to a full life, depressive disorders are ahead of all other mental illnesses, including Alzheimer's disease, alcoholism and schizophrenia. Depressions are fourth among all diseases according to the integrated assessment of the burden that society bears in connection with them. Thus, A. Nierenberg (2001) notes that in America about 6 million people suffer from depression every year, and more than 16 billion dollars are spent on their treatment. By 2020, depressive disorders will already be in second place according to this criterion, second only to ischemic heart disease.

It is clear from this that the development of effective methods of therapy and prevention of depressive disorders is one of the most important tasks of modern psychiatry. It would not be an exaggeration to call this task the cornerstone of mental health protection in the 21st century. The solution to such a complex problem requires taking into account the various factors that contribute to the emergence of depressions, affect their course, determine their prognosis and the effectiveness of treatment. Among these, of course, are ethnocultural factors, the role of which in the etiopathogenesis of depression is recognized today by almost all researchers. In particular, American psychiatrists L. J. Kirmayer and D. Groleau (2001) argue that the presence of ethnographic knowledge is a necessary condition for understanding the causes, semiology and course of depressive disorders.

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Current state of research on depressive disorders

As already noted, in recent decades, a trend towards an increase in the incidence of depressive disorders has been determined throughout the world. According to epidemiological studies conducted under the auspices of the WHO, based on a random examination of patients in the general medical network in 14 countries, the average prevalence of depression in the last decade of the 20th century compared to the 1960s (0.6%) was 10.4%. Thus, over the past 30 years, the number of patients with depressive disorders has increased more than 17 times.

Prevalence of depression in primary care (WHO data)

Country	Depressive disorders, %
Japan	2.6
India	9.1
China	4.0
Germany	11.2
Nigeria	4.2
France	13.7
Türkiye	4.2
Brazil	15.8
Italy	4.7
Netherlands	15.9
USA	6.3
England	16.9
Greece	6.4
Chile	29.5
Average rate	10.4

Taking into account that the identification and clinical qualification of depressive disorders were carried out within the framework of one program according to uniform methodological and clinical diagnostic criteria and using a common tool, a significant (10 times or more) spread of depression prevalence rates in different countries of the world is noteworthy: from 2.6% in Japan to 29.5% in Chile. At the same time, it seems difficult to identify any patterns of differences. One can only cautiously say about the tendency of lower prevalence of depressive disorders in Asian, African and North American countries, as well as in the countries of Southern Europe and higher prevalence in the countries of Western Europe and Latin America. As for the levels of socio-political stability and economic development of the analyzed countries, no connection between the prevalence of depressive disorders and these rates was found. The data obtained may indicate a certain role of ethnocultural factors in the emergence and prevalence of depressive pathology.

Many researchers believe that the real prevalence of depression may be even higher if we take into account cases of so-called depressive spectrum disorders - some forms of pathology of desires, dependence on alcohol and psychoactive substances, somatoform, psychosomatic and neurotic disorders occurring with depressive symptoms.

Thus, according to the results of a random examination of 226 people in general medical care institutions conducted in the USA, 72% of them showed signs of mild depression observed over 4 weeks - depressed mood, cognitive impairment and individual vegetative manifestations. Of these, 10% had a history of major depressive disorders, and almost half of the cases had a hereditary burden of unipolar depression. Based on this, the authors made the following conclusions:

1. in the clinical picture of mild depression, depressed mood and cognitive impairment predominate, while vegetative symptoms are much less common;
2. mild depression may occur either as an independent disease or as a stage of recurrent unipolar depressive disorder;
3. Mild depressions should be considered within a continuum of 'clinical severity'.

According to domestic researchers, in Russia about half of people who visit local polyclinics have some signs of depressive disorders. The prevalence of mild depressive disorders, mixed anxiety-depressive states and their occurrence in somatic diseases reaches even greater values.

The clinical structure of depressions first identified in patients of the general somatic network, according to the results of a study conducted in Moscow by M.N. Bogdan (1998): depressive episode - 32.8%, recurrent depressive disorder - 29%, chronic affective disorders, including cyclothymia and dysthymia - 27.3%, bipolar affective disorder - 8.8% of cases.

Almost all researchers recognize the role of age and gender in the occurrence and prevalence of depressive disorders. According to WHO (2001), depressions most often develop in adulthood. At the same time, in the age group of 15 - 44 years, these disorders are the second most severe burden, accounting for 8.6% of the number of years of life lost as a result of disability. In addition, the literature contains information on the presence of ethnocultural differences in relation to the age-related preference for the occurrence of depressive states.

Thus, if in a number of African countries (Laos, Nigeria) there is a predominance of mature age people - 30-45 years old - among those suffering from depressive disorders, then in the USA these diseases most often develop in "adult teenagers". In support of this, we can cite the data of the analytical review by P.I. Sidorov (2001), from which it follows that in the USA 5% of the population aged 9 to 17 years suffer from depression, and in Ehmre - 10% of the total number of all schoolchildren. In most European countries, the highest prevalence of depressive disorders is found in elderly people. This is due to the accumulation of life difficulties and a decrease in psychological stability inherent in this age.

Gender specificities of depression prevalence are reflected in the WHO (2001) data, according to which the prevalence of depression in most countries of the world is higher among women. Thus, the average frequency of unipolar depressive disorder is 1.9% in men and 3.2% in women, and the first-time depressive episode is 5.8% and 9.5%, respectively.

Among the social factors that contribute to the development of depression, poverty and the associated unemployment, low educational level, and homelessness stand out. All these factors are the lot of a significant part of people in countries with contrasting income levels. Thus, according to the results of transnational studies conducted in Brazil, Chile, India, and Zimbabwe, depressive disorders are on average 2 times more common in low-income population groups than among the rich.

According to the unanimous opinion of researchers, in all countries people with depressive disorders have the highest risk of committing suicide. We will consider this aspect of the problem in more detail in the corresponding section of this book. Here we will limit ourselves to only a few figures confirming the correctness of this conclusion. According to world literature, among all suicides, the proportion of people with depression is 35% in Sweden, 36% in the USA, 47% in Spain, 67% in France. There is also information that 15-20% of patients suffering from depression commit suicide.

Much less frequently, information about the ethnocultural features of the clinical picture of depressive disorders is found in the literature. In this regard, comparative studies of clinical manifestations of depression in Eastern and Western cultures deserve attention.

Most authors note that in Eastern cultures depressions are much more often of a somatized nature. In our country, V.B. Minevich (1995) and P.I. Sidorov (1999) came to a similar conclusion, having established, respectively, that the Buryats and small peoples of the Russian North develop almost exclusively somatized depressions, which significantly complicates their timely detection and treatment. V.B. Minevich explained this phenomenon by the fact that complaints of the depressive spectrum (depressed mood, oppression, melancholy) are absolutely abnormal in the Eastern culture, to which the Buryat culture belongs. Based on this, depressions in Eastern ethnic groups initially acquire a somatized character.

The presented data are indirectly confirmed by the results of a number of foreign studies concerning chronic depressive disorder - dysthymia. It is generally accepted that the prevalence of this disease in different countries of the world is approximately the same and averages 3.1%. At the same time, according to L. Waintraub and J. D. Guelfi (1998), in Eastern countries the corresponding indicators are significantly lower, for example, in Taiwan they are only 1%. However, it remains unclear whether dysthymia is actually less common in the East or whether it is simply not recognized due to its somatization.

Thus, there are scientifically confirmed differences in the prevalence and clinical manifestations of depressive disorders in Eastern and Western cultures. In addition, there is information in the literature about the existence of "internal" (subcultural) differences in each of these cultures. This is the subject of the original work of the Russian researcher L.V. Kim (1997), who studied the clinical and epidemiological features of depression among adolescents of ethnic Koreans living in Uzbekistan (Tashkent) and the Republic of Korea (Seoul).

The author found that the prevalence of actively identified depressive disorders in the general population of adolescents in Seoul (33.2%) is almost 3 times higher than the same indicator in Tashkent (11.8%). This is a reliable indicator, since the study was carried out using uniform methodological approaches and was based on common clinical criteria.

According to L.V. Kim, the higher prevalence of depression among adolescents in South Korea is due to socio-environmental factors. In recent decades, the country has adopted the idea of an inextricable link between a prestigious position in society and higher education, so the number of applicants is many times greater than the number of places in universities, and the requirements for students are becoming increasingly high. Against this background, the so-called "pressure of success" is formed, which is manifested, on the one hand, by the desire of the teenager to achieve success and the desire to meet the demands of his parents; on the other hand, by the presence of fear, anxiety, expectation of failure and failure. Due to this, "pressure of success" is becoming one of the most powerful risk factors for the development of depression in South Korean adolescents.

The author believes that additional arguments in favor of the depressogenic role of “pressure of success” in the contingent of adolescents living in Seoul are:

1. a higher proportion of males among “depressed teenagers” as a consequence of the traditional South Korean focus on achieving social and professional success by men;
2. the dependence of depression on the presence of a particular chronic somatic disease that prevents the teenager from achieving social success and career aspirations;
3. a significant (more than 2 times) predominance of high-achieving students among “depressed teenagers” in Seoul compared to the corresponding group in Tashkent, which reflects a higher level of socially determined aspirations in a competitive society.

As for other pathogenic socio-psychological factors, adolescents from Uzbekistan suffering from depression, compared to their peers from Seoul, are significantly more likely to have interpersonal problems, including with parents (4.2 times), teachers (3.6 times), siblings (6 times), and peers (3.3 times). This can be explained by certain subcultural differences between representatives of the metropolis and the diaspora. In particular, unlike Uzbekistan, adolescents in Korea are brought up on the traditions of Buddhism, which condemn open displays of aggression and conflict. Analysis of other sociodemographic and socio-psychological factors did not establish their significant connection with the formation of depressive disorders in adolescents both in Korea and Uzbekistan.

In clinical terms, when studying depressive disorders in adolescents of the compared subpopulations, no ethnocultural features or differences were found. The most common typological variants of depression are melancholy depression (28.4%), astheno-apathetic (20.9%), anxious (16.4%), with psychopathic manifestations (13.4%), with dysmorphophobic syndrome (11.9%), with somatovegetative disorders (9%). According to the clinical criteria of DSM-1V, almost half of all cases were mild depressions (Mild) - 49.3%, followed by moderate depressions (Moderate) - 35.1% and the smallest proportion falls on severe depressions (Severe) - 15.6%.

Thus, the prevalence, conditions of formation, and clinical manifestations of depressive disorders may have not only ethnocultural but also ethnosubcultural differences, knowledge of which is important for psychiatrists.

In Russian psychiatry, ethnocultural studies of depressive disorders are very few. In this regard, one can note a cycle of comparative transcultural studies of depressions carried out by O.P. Vertogradova et al. (1994, 1996). In one of the works, the authors studied the cultural characteristics of depressive disorders in the indigenous population of the Republic of North Ossetia (Alania). A feature of the Ossetians is that, although they live in the North Caucasus, they do not belong to the peoples of the North Caucasian family. By their ethnicity, the Ossetians are part of the Iranian ethnic group, along with the Tajiks, Afghans, and Kurds. The study found that Ossetians suffering from depressive disorders, compared to Russian patients, have a higher level of ideational components of depression, dysphoric disorders, alexithymia, vagotonic symptoms, and somatic components.

In another study by this group of authors, a comparative clinical and epidemiological analysis of depressions in Russian (Moscow) and Bulgarian (Sofia) populations was conducted. The object of the study was patients with depressive disorders identified in general somatic outpatient clinics. According to the basic clinical parameters (hypothymia, anxiety, exhaustion, vitalization of affect, daily mood swings, sleep disorders), patients of the compared nationalities are practically the same. At the same time, Russian patients more often exhibit ideas of insignificance, anhedonia, faint-heartedness, narrowing of the range of associations, and Bulgarian patients - bodily sensations.

Among the latest works concerning the ethnocultural aspects of depressive pathology, the study by O.I. Khvostova (2002) attracts attention. She studied depressive disorders in the Altai people, a small people indigenous to the Altai Republic and belonging to the Turkic ethnic group. Their peculiarity is the presence of sub-ethnic groups living in different climatic and geographic conditions: the Telengit sub-ethnic group, which is formed by the inhabitants of the "highlands" (altitude up to 2,500 m above sea level, extreme climate, equivalent to the regions of the Far North), and the Altai-Kizhi sub-ethnic group. The specificity of the latter is that one part of it lives in the conditions of the "middle mountains" (altitude up to 1000 m above sea level), and the other - the "low mountains" (intermountain valleys at an altitude of up to 500 m above sea level with a relatively favorable climate).

The study found that the prevalence of depressive disorders among Altai residents reaches a fairly high value - 15.6 per 100 surveyed. In women, depressive disorders occur 2.5 times more often than in men. Of interest are the differences in the morbidity of depressive disorders among representatives of Altai subethnic groups. The maximum level is noted among residents of the "highlands" (19.4%), then among residents of the "middle mountains" (15.3%), and the lowest level is recorded among the subethnic group living in more favorable conditions of the "low mountains" (12.7%). Thus, the prevalence of depressive disorders within the same ethnic group to a certain extent depends on climatic and geographical conditions and the degree of social comfort of living.

In conclusion of a brief analysis of the literature on the ethnocultural characteristics of depressive disorders, it is easy to conclude that, despite the unconditional significance of these aspects, they continue to remain insufficiently studied both in global and domestic psychiatry.