8 Chapter 1 THE HIGH BURDEN OF MENTAL DISORDERS AND ITS DISTRIBUTION Mental disorders pose an extremely high burden to society, both in terms of their direct impact on health but also in terms of societal welfare losses [1]. According to the most recent estimates of the Global Burden of Disease (GBD) study, mental disorders rank as the second cause of years lived with disability (YLDs) worldwide and the seventh cause of disability-adjusted life years (DALYs; the sum of YLDs and years of life lost (YLLs)) [2]. The main contributors to this burden are depression (37% of DALYs) and anxiety (23%) due to their high prevalence, followed by schizophrenia (12%) due to extremely disabling states of acute psychosis. Importantly, recent studies point towards a systematic underestimation of mental health burden mainly through unaccounted YLLs. According to these estimates, the actual burden should be at least two to three times higher than the conventional results, making mental disorders responsible for 13% to 16% of all DALYs worldwide [3, 4]. This population health burden translates into substantial economic consequences. Mental disorders are costly not only due to their direct medical costs, such as outpatient care and hospitalisations but mainly due to indirect costs, such as losses in labour productivity and income resulting from absenteeism and presentism [3]. Disability resulting from mental health disorders reduces countries´ economic output by undermining labour and capital supply and contributes to the persistence of the vicious poverty and illness cycle. A recent estimate of the economic value associated with mental disorders suggests global losses of 4.7 trillion US dollars (USD) in 2019, ranging from 4% of the gross domestic product (GDP) in Eastern Sub-Saharan Africa to 8% in North America [3]. Mental health is a global public good and a vital determinant of every country’s sustainable development, regardless of its level of development. In fact, in what concerns addressing population mental health, all countries qualify as developing countries [1]. Within countries, the distribution of mental disorders burden varies substantially by age, gender, and socioeconomic status. The number of DALYs increases consistently during childhood and adolescence, peaks for the age group of 25 to 34 years, and decreases steadily from there onwards [2]. Mental disorders are the leading cause of disability among adolescents and young adults in high-income countries [5, 6]. Approximately 75% of adult mental disorders have their onset during adolescence, increasing the risk of recurrence and disabling physical1 conditions in adulthood [6, 7]. Gender patterns are also marked, at least for some conditions. Females have the highest prevalence and burden of depressive, anxiety and eating disorders. Males have the highest prevalence 1 For the lack of a better term I use physical conditions / diseases / disorders to refer to all the other disorders that are not mental or neurological. The reader should, however, be aware of the limitations of using such terminology. Referring to physical or somatic disorders as the opposite of mental disorders perpetuates the idea that the later are not equally attributable to our phenotype; supporting the segregation of mental disorders that has made these neglected for decades.
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