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

Some common disorders

  Chapter 2

Mental and behavioural disorders present a varied and heterogeneous picture. Some disorders are mild while others are severe. Some last just a few weeks while others may last a lifetime. Some are not even discernible except by detailed scrutiny while others are impossible to hide even from a casual observer. This report focuses on a few common disorders that place a heavy burden on communities and that are generally regarded with a high level of concern. These include depressive disorders, substance use disorders, schizophrenia, epilepsy, Alzheimer's disease, mental retardation, and disorders of childhood and adolescence. The inclusion of epilepsy needs some explanation. Epilepsy is a neurological disorder and is classified under Chapter VI of ICD-10 with other diseases of the nervous system. However, epilepsy was historically seen as a mental disorder and is still considered this way in many societies. Like those with mental disorders, people with epilepsy suffer stigma and severe disability if left untreated. The management of epilepsy is often the responsibility of mental health professionals because of the high prevalence of this disorder and the relative scarcity of specialist neurological services, especially in developing countries. In addition, many countries have laws that prevent individuals with mental disorders and epilepsy from undertaking certain civil responsibilities.

The following section briefly describes the basic epidemiology, burden, course/outcome and special characteristics of some disorders, as examples, to provide background to the discussion of available interventions (in Chapter 3) and mental health policy and programmes (in Chapter 4).

Depressive disorders

Depression is characterized by sadness, loss of interest in activities, and decreased energy. Other symptoms include loss of confidence and self-esteem, inappropriate guilt, thoughts of death and suicide, diminished concentration, and disturbance of sleep and appetite. A variety of somatic symptoms may also be present. Though depressive feelings are common, especially after experiencing setbacks in life, depressive disorder is diagnosed only when the symptoms reach a threshold and last at least two weeks. Depression can vary in severity from mild to very severe (see Figure 1.3). It is most often episodic but can be recurrent or chronic. Depression is more common in women than in men. GBD 2000 estimates the point prevalence of unipolar depressive episodes to be 1.9% for men and 3.2% for women, and that 5.8% of men and 9.5% of women will experience a depressive episode in a 12-month period. These prevalence figures vary across populations and may be higher in some populations.

GBD 2000 analysis also shows that unipolar depressive disorders place an enormous burden on society and are ranked as the fourth leading cause of burden among all diseases, accounting for 4.4% of the total DALYs and the leading cause of YLDs, accounting for 11.9% of total YLDs. In the age group 15­44 years it caused the second highest burden, amounting to 8.6% of DALYs lost. While these estimates clearly demonstrate the current very high level of burden resulting from depression, the outlook for the future is even grimmer. By the year 2020, if current trends for demographic and epidemiological transition continue, the burden of depression will increase to 5.7% of the total burden of disease, becoming the second leading cause of DALYs lost. Worldwide it will be second only to ischaemic heart disease for DALYs lost for both sexes. In the developed regions, depression will then be the highest ranking cause of burden of disease.

Depression can affect individuals at any stage of the life span, although the incidence is highest in the middle ages. There is, however, an increasing recognition of depression during adolescence and young adulthood (Lewinsohn et al. 1993). Depression is essentially an episodic recurring disorder, each episode lasting usually from a few months to a few years, with a normal period in between. In about 20% of cases, however, depression follows a chronic course with no remission (Thornicroft & Sartorius 1993), especially when adequate treatment is not available. The recurrence rate for those who recover from the first episode is around 35% within 2 years and about 60% at 12 years. The recurrence rate is higher in those who are more than 45 years of age. One of the particularly tragic outcomes of a depressive disorder is suicide. Around 15­20% of depressive patients end their lives by committing suicide (Goodwin & Jamison 1990). Suicide remains one of the common and avoidable outcomes of depression.

Bipolar affective disorder refers to patients with depressive illness along with episodes of mania characterized by elated mood, increased activity, over-confidence and impaired concentration. According to GBD 2000, the point prevalence of bipolar disorder is around 0.4%.

To summarize, depression is a common mental disorder, causing a very high level of disease burden, and is expected to show a rising trend during the coming 20 years.

Substance use disorders

Mental and behavioural disorders resulting from psychoactive substance use include disorders caused by the use of alcohol, opioids such as opium or heroin, cannabinoids such as marijuana, sedatives and hypnotics, cocaine, other stimulants, hallucinogens, tobacco and volatile solvents. The conditions include intoxication, harmful use, dependence and psychotic disorders. Harmful use is diagnosed when damage has been caused to physical or mental health. Dependence syndrome involves a strong desire to take the substance, difficulty in controlling use, a physiological withdrawal state, tolerance, neglect of alternative pleasures and interests, and persistence of use despite harm to oneself and others.

Though the use of substances (along with their associated disorders) varies from region to region, tobacco and alcohol are the substances that are used most widely in the world as a whole and that have the most serious public health consequences.

Use of tobacco is extremely common. Most of the use is in the form of cigarettes. The World Bank estimates that, in high income countries, smoking-related health care accounts for 6­15.1% of all annual health care costs (World Bank 1999).

Today, about one in three adults, or 1.2 billion people, smoke. By 2025, the number is expected to rise to more than 1.6 billion. Tobacco was estimated to account for over 3 million annual deaths in 1990, rising to 4 million annual deaths in 1998. It is estimated that tobacco-attributable deaths will rise to 8.4 million in 2020 and reach 10 million annual deaths in about 2030. This increase will not, however, be shared equally: deaths in developed regions are expected to rise 50% from 1.6 to 2.4 million, while those in Asia will soar almost fourfold from 1.1 million in 1990 to an estimated 4.2 million in 2020 (Murray & Lopez 1997).

In addition to the social and behavioural factors associated with the onset of tobacco use, a clear dependence on nicotine is found in the majority of chronic smokers. This dependence prevents these individuals from giving up tobacco use and staying away from it. Box 2.3 describes the link between mental disorders and tobacco use.

Box 2.3 Tobacco use and mental disorders

The link between tobacco use and mental disorders is a complex one. Research findings strongly suggest that mental health professionals need to pay much greater attention to tobacco use by patients during and after their treatment, in order to prevent related problems.

People with mental disorders are about twice as likely to smoke as others; those with schizophrenia and alcohol dependence are particularly likely to be heavy smokers, with rates as high as 86%.1­3 A recent study in the USA showed that individuals with current mental disorders had a smoking rate of 41% compared with 22.5% in the general population, and estimated that 44% of all cigarettes smoked in the US are consumed by people with mental disorders.4

Regular smoking starts earlier in male adolescents with attention deficit disorder,5 and individuals with depression are also more likely to be smokers.6 Though the traditional thinking has been that depressed individuals tend to smoke more because of their symptoms, new evidence reveals that it may be the other way round. A study of teenagers showed that those who became depressed had a higher prevalence of smoking beforehand ­ suggesting that smoking actually resulted in depression in this age group.7

Alcohol and drug use disorder patients also show systematic changes in their smoking behaviour during treatment. A recent study found that though heavy smokers decreased their smoking while hospitalized for detoxification, light smokers actually increased their smoking substantially.8

The reasons for the high rate of smoking by persons with mental and behavioural disorders are not clearly known, but neurochemical mechanisms have been suggested to account for it.9 Nicotine is a highly psychoactive chemical that has a variety of effects in the brain: it has reinforcing properties and activates the reward systems of the brain; it also leads to increased dopamine release in parts of the brain that are intimately related to mental disorders. Nicotine may also be consumed in an attempt to decrease the distress and other undesirable effects of mental symptoms. Social environment, including isolation and boredom, may also play a role; these aspects are particularly evident in an institutional setting. Whatever the reasons, the fact that people with mental disorders further jeopardize their health by excessive smoking is not in doubt.

1Hughes JR et al. (1986). Prevalence of smoking among psychiatric outpatients. American Journal of Psychiatry,143: 993-997.

2Goff DC et al. (1992). Cigarette smoking in schizophrenia: relationship to psychopathology and medication side-effects. American Journal of Psychiatry, 149: 1189-1194.

3True WR et al. (1999). Common genetic vulnerability for nicotine and alcohol dependence in men. Archives of General Psychiatry, 56: 655-661.

4Lasser K et al. (2000). Smoking and mental illness: a population-based prevalence study. Journal of the American Medical Association, 284: 2606-2610.

5Castellanos FX et al. (1994). Quantitative morphology of the caudate nucleus in attention deficit hyperactivity disorder. American Journal of Psychiatry, 151(12): 1791-1796.

6Pomerleau OF et al. (1995). Cigarette smoking in adult patients diagnosed with attention deficit hyperactivity disorder. Journal of Substance Abuse, 7(3): 373-368.

7Goodman E, Capitman J (2000). Depressive symptoms and cigarette smoking among teens. Pediatrics 106(4): 748-755.

8Harris J et al. (2000). Changes in cigarette smoking among alcohol and drug misusers during inpatient detoxification. Addiction Biology, 5: 443-450.

9Batra A (2000). Tobacco use and smoking cessation in the psychiatric patient. Forschritte de Neurologie-Psychiatrie, 68: 80-92.

Alcohol is also a commonly used substance in most regions of the world. Point prevalence of alcohol use disorders (harmful use and dependence) in adults has been estimated to be around 1.7% globally according to GBD 2000 analysis. The rates are 2.8% for men and 0.5% for women. The prevalence of alcohol use disorders varies widely across different regions of the world, ranging from very low levels in some Middle Eastern countries to over 5% in North America and parts of Eastern Europe.

Alcohol use is rising rapidly in some of the developing regions of the world (Jernigan et al. 2000; Riley & Marshall 1999; WHO 1999) and this is likely to escalate alcohol-related problems (WHO 2000b). Alcohol use is also a major reason for concern among the indigenous people around the world, who show a higher prevalence of use and associated problems.

Alcohol ranks high as a cause of disease burden. The global burden of disease project (Murray & Lopez 1996a) estimated alcohol to be responsible for 1.5% of all deaths and 3.5% of the total DALYs. This burden includes physical disorders (such as cirrhosis), and injuries (for example, motor vehicle crash injuries) attributable to alcohol.

Alcohol imposes a high economic cost on society. One estimate puts the yearly economic cost of alcohol abuse in the United States to be US$ 148 billion, including US$ 19 billion for health care expenditure (Harwood et al. 1998). In Canada, the economic costs of alcohol, tobacco and illicit drugs in 1992 amounted to Canadian Dollars 18.4 billon, representing 2.7% of the gross domestic product. Alcohol alone was responsible for Canadian Dollars 7.52 billion as costs. Studies in other countries have estimated the cost of alcohol-related problems to be around 1% of the gross domestic product (Collins & Lapsely 1996; Rice et al. 1991). A recent study demonstrated that alcohol-related hospital charges in 1998 in New Mexico, USA, were US$ 51 million in comparison to US$ 35 million collected as alcohol taxes (New Mexico Department of Health 2001), clearly showing that communities spend more money on taking care of alcohol problems than they earn from alcohol.

Besides tobacco and alcohol, a large number of other substances ­ generally grouped under the broad category of drugs ­ are also abused. These include illicit drugs such as heroin, cocaine and cannabis. The period prevalence of drug abuse and dependence ranges from 0.4% to 4%, but the type of drugs used varies greatly from region to region. GBD 2000 analysis suggests that the point prevalence of heroin and cocaine use disorders is 0.25%. Injecting drugs involves considerable risk of infections, including hepatitis B, hepatitis C and HIV. It has been estimated that there are about 5 million people in the world who inject illicit drugs. The prevalence of HIV infection among injecting drug users is 20­80% in many cities. The increasing role of injecting drug use in HIV transmission has attracted serious concern all over the world, especially in Central and Eastern European countries (UNAIDS 2000).

The burden attributable to illicit drugs (heroin and cocaine) was estimated at 0.4% of the total disease burden according to GBD 2000. The economic cost of harmful drug use and dependence in the United States has been estimated to be US$ 98 billion (Harwood et al. 1998). These disease burden and cost estimates do not take into account a variety of negative social effects that are caused by drug use. Tobacco and alcohol use typically starts during youth and acts as a facilitator to the use of other drugs. Thus tobacco and alcohol contribute indirectly to a large amount of the burden of other drugs and the consequent diseases.

Questions are often raised as to whether substance use disorders are genuine disorders or should rather be seen as deviant behaviour by people who deliberately indulge in an activity that causes them harm. While deciding to experiment with a psychoactive substance is usually a personal decision, developing dependence after repeated use is not a conscious and informed decision by the individual or the result of a moral weakness, but the outcome of a complex combination of genetic, physiological and environmental factors. It is very difficult to distinguish exactly when a person becomes dependent on a substance (regardless of its legal status), and there is evidence that dependence is not a clearly demarcated category but that it happens along a continuum, from early problems without significant dependence to severe dependence with physical, mental and socioeconomic consequences.

There is also increasing evidence of neurochemical changes in the brain that are associated with and indeed cause many of the essential characteristics of substance dependence. Even the clinical evidence suggests that substance dependence should be seen as both a chronic medical illness and a social problem (Leshner 1997; McLellan et al. 2000). Common roots of dependence for a variety of substances and the high prevalence of multiple dependence also suggest that substance dependence should be viewed as a complex mental disorder with a possible basis in brain functioning.


Schizophrenia is a severe disorder that typically begins in late adolescence or early adulthood. It is characterized by fundamental distortions in thinking and perception, and by inappropriate emotions. The disturbance involves the most basic functions that give the normal person a feeling of individuality, uniqueness and self-direction. Behaviour may be seriously disturbed during some phases of the disorder, leading to adverse social consequences. Strong belief in ideas that are false and without any basis in reality (delusions) is another feature of this disorder.

Schizophrenia follows a variable course, with complete symptomatic and social recovery in about one-third of cases. Schizophrenia can, however, follow a chronic or recurrent course, with residual symptoms and incomplete social recovery. Individuals with chronic schizophrenia constituted a large proportion of all residents of mental institutions in the past, and still do where these institutions continue to exist. With modern advances in drug therapy and psychosocial care, almost half the individuals initially developing schizophrenia can expect a full and lasting recovery. Of the remainder, only about one-fifth continue to face serious limitations in their day-to-day activities.

Schizophrenia is found approximately equally in men and women, though the onset tends to be later in women, who also tend to have a better course and outcome of this disorder.

GBD 2000 reports a point prevalence of 0.4% for schizophrenia. Schizophrenia causes a high degree of disability. In a recent 14-country study on disability associated with physical and mental conditions, active psychosis was ranked the third most disabling condition, higher than paraplegia and blindness, by the general population (Üstün et al. 1999).

In the global burden of disease study, schizophrenia accounted for 1.1% of the total DALYs and 2.8% of YLDs. The economic cost of schizophrenia to society is also high. It has been estimated that, in 1991, the cost of schizophrenia to the United States was US$ 19 billion in direct expenditure and US$ 46 billion in lost productivity.

Even after the more obvious symptoms of this disorder have disappeared, some residual symptoms may remain. These include lack of interest and initiative in daily activities and work, social incompetence, and inability to take interest in pleasurable activities. These can cause continued disability and poor quality of life. These symptoms can place a considerable burden on families (Pai & Kapur 1982). It has been repeatedly demonstrated that schizophrenia follows a less severe course in developing countries (Kulhara & Wig 1978; Thara & Eaton 1996). For example, in one of the multi-site international studies, the proportion of patients showing full remission at 2 years was 63% in developing countries compared to 37% in developed countries (Jablensky et al. 1992). Though attempts have been made to explain this better outcome on the basis of stronger family support and fewer demands on the patients, the exact reasons for these differences are not clear.

A substantial number of individuals with schizophrenia attempt suicide at some time during the course of their illness. A recent study showed that 30% of patients diagnosed with this disorder had attempted suicide at least once during their lifetime (Radomsky et al. 1999). About 10% of persons with schizophrenia die by suicide (Caldwell & Gottesman 1990). Globally, schizophrenic illness reduces an affected individual's lifespan by an average of 10 years.


Epilepsy is the most common brain disorder in the general population. It is characterized by recurrence of seizures, caused by outbursts of excessive electrical activity in part or the whole of the brain. The majority of individuals with epilepsy do not have any obvious or demonstrable abnormality in the brain, besides the electrical changes. However, a proportion of individuals with this disorder may have accompanying brain damage, which may cause other physical dysfunctions such as spasticity or mental retardation.

The causes of epilepsy include genetic predisposition, brain damage caused by birth complications, infections and parasitic diseases, brain injuries, intoxication and tumours. Cysticercosis (tapeworm), schistosomiasis, toxoplasmosis, malaria, and tubercular and viral encephalitis are some of the common infectious causes of epilepsy in developing countries (Senanayake & Román 1993). Epileptic seizures vary greatly in frequency, from several a day to once every few months. The manifestation of epilepsy depends on the brain areas involved. Usually the individual undergoes sudden loss of consciousness and may experience spasmodic movements of the body. Injuries can result from a fall during the seizure.

GBD 2000 estimates that about 37 million individuals globally suffer from primary epilepsy. When epilepsy caused by other diseases or injury is also included, the total number of persons affected increases to about 50 million. It is estimated that more than 80% individuals with epilepsy live in developing countries.

Epilepsy places a significant burden on communities, especially in developing countries where it may remain largely untreated. GBD 2000 estimates the aggregate burden due to epilepsy to be 0.5% of the total disease burden. In addition to physical and mental disability, epilepsy often results in serious psychosocial consequences for the individual and the family. The stigma attached to epilepsy prevents individuals with epilepsy from participating in normal activities, including education, marriage, work and sports.

Epilepsy typically arises during childhood and can (though does not always) follow a chronic course. The rate of spontaneous recovery is substantial, with many of those initially identified as suffering from epilepsy being free from seizure after three years.

Alzheimer's disease

Alzheimer's disease is a primary degenerative disease of the brain. Dementia in Alzheimer's disease is classified as a mental and behavioural disorder in ICD-10. It is characterized by progressive decline of cognitive functions such as memory, thinking, comprehension, calculation, language, learning capacity and judgement. Dementia is diagnosed when these declines are sufficient to impair personal activities of daily living. Alzheimer's disease shows insidious onset with slow deterioration. This disease needs to be clearly differentiated from age-related normal decline of cognitive functions. The normal decline is much less, much more gradual and leads to milder disabilities. The onset of Alzheimer's disease is usually after 65 years of age, though earlier onset is not uncommon. As age advances, the incidence increases rapidly (it roughly doubles every 5 years). This has obvious implications for the total number of individuals living with this disorder as life expectancy increases in the population.

The incidence and prevalence of Alzheimer's disease have been studied extensively. The population samples are usually composed of people over 65 years of age, although some studies have included younger populations, especially in countries where the expected life span is shorter (for example, India). The wide range of prevalence figures (1­5%) is partly explained by the different age samples and diagnostic criteria. In GBD 2000, Alzheimer's and other dementias have an overall point prevalence of 0.6%. The prevalence among those above 60 years is about 5% for men and 6% for women. There is no evidence of any sex difference in incidence, but more women are encountered with Alzheimer's disease because of greater female longevity.

The exact cause of Alzheimer's disease remains unknown, although a number of factors have been suggested. These include disturbances in the metabolism and regulation of amyloid precursor protein, plaque-related proteins, tau proteins, zinc and aluminium (Drouet et al. 2000; Cuajungco & Lees 1997).

GBD 2000 estimates the DALYs due to dementias as 0.84% and YLDs as 2.0%. With the ageing of populations, especially in the industrialized regions, this percentage is likely to show a rapid increase in the next 20 years.

The cost of Alzheimer's disease to society is already massive (Rice et al. 1993) and will continue to increase (Brookmeyer & Gray 2000). The direct and total costs of this disorder in the United States have been estimated to be US$ 536 million and US$ 1.75 billion, respectively, for the year 2000.

Mental retardation

Mental retardation is a condition of arrested or incomplete development of the mind characterized by impairment of skills and overall intelligence in areas such as cognition, language, and motor and social abilities. Also referred to as intellectual disability or handicap, mental retardation can occur with or without any other physical or mental disorders. Although reduced level of intellectual functioning is the characteristic feature of this disorder, the diagnosis is made only if it is associated with a diminished ability to adapt to the daily demands of the normal social environment. Mental retardation is further categorized as mild (IQ levels 50-69), moderate (IQ levels 35­49), severe (IQ levels 20­34), and profound (IQ levels below 20).

The prevalence figures vary considerably because of the varying criteria and methods used in the surveys, as well as differences in the age range of the samples. The overall prevalence of mental retardation is believed to be between 1% and 3%, with the rate for moderate, severe and profound retardation being 0.3%. It is more common in developing countries because of the higher incidence of injuries and anoxia around birth, and early childhood brain infections. A common cause of mental retardation is endemic iodine deficiency, which leads to cretinism (Sankar et al. 1998). Iodine deficiency constitutes the world's greatest single cause of preventable brain damage and mental retardation (Delange 2000).

Mental retardation places a severe burden on the individual and the family. For more severe retardation, this involves assistance in carrying out daily life activities and self care. No estimates are available for the overall disease burden of mental retardation, but all evidence points towards a substantial burden caused by this condition. In most cases, this burden continues throughout life.

Disorders of childhood and adolescence

Contrary to popular belief, mental and behavioural disorders are common during childhood and adolescence. Inadequate attention is paid to this area of mental health. In a recent report, the Surgeon General of the United States (DHHS 2001) has said that the United States is facing a public crisis in mental health of infants, children and adolescents. According to the report, one in ten young people suffers from mental illness severe enough to cause some level of impairment, yet fewer than one in five receives the needed treatment. The situation in large parts of the developing world is likely to be even more unsatisfactory.

ICD-10 identifies two broad categories specific to childhood and adolescence: disorders of psychological development, and behavioural and emotional disorders. The former are characterized by impairment or delay in the development of specific functions such speech and language (dyslexias) or overall pervasive development (for example, autism). The course of these disorders is steady, without remission or relapses, though most tend to improve with time. The broad group of dyslexias consists of reading and spelling disorders. The prevalence of these disorders is still uncertain, but it may be about 4% for the school-age population (Spagna et al. 2000). The second category, behavioural and emotional disorders, includes hyperkinetic disorders (in ICD-10), attention deficit/hyperactivity disorder (in DSM-IV, APA 1994), conduct disorders and emotional disorders of childhood. In addition, many of the disorders more commonly found among adults can begin during childhood. An example is depression, which is increasingly being identified among children.

The overall prevalence of mental and behavioural disorders among children has been investigated in several studies from developed and developing countries. The results of selected studies are summarized in Table 2.2. Though the prevalence figures vary considerably between studies, it seems that 10­20% of all children have one or more mental or behavioural problems. A caveat must be made to these high estimates of morbidity among children and adolescents. Childhood and adolescence being developmental phases, it is difficult to draw clear boundaries between phenomena that are part of normal development and others that are abnormal. Many studies have used behavioural checklists completed by parents and teachers to detect cases. This information, though useful in identifying children who may need special attention, may not always correspond to a definite diagnosis.

Table 2.2 Prevalence of child and adolescent disorders, selected studies

Country Age (years) Prevalence (%)
Ethiopia1 1­15 17.7
Germany2 12­15 20.7
India3 1­16 12.8
Japan4 12­15 15
Spain 5 8, 11, 15 21.7
Switzerland6 1­15 22.5
USA7 1­15 21
1Tadesse B et al. (1999). Childhood behavioural disorders in Ambo district, Western Ethiopia: I. Prevalence estimates. Acta Psychiatrica Scandinavica, 100(Suppl): 92-97.
2Weyerer S et al. (1988). Prevalence and treatment of psychiatric disorders in 3­14-year-old children: results of a representative field study in the small rural town region of Traunstein, Upper Bavaria. Acta Psychiatrica Scandinavica, 77: 290-296.
3Indian Council of Medical Research (2001). Epidemiological study of child and adoles-cent psychiatric disorders in urban and rural areas. New Delhi, ICMR (unpublished data).
4Morita H et al. (1993). Psychiatric disorders in Japanese secondary school children. Journal of Child Psychology and Psychiatry, 34: 317-332.
5Gomez-Beneyto M et al. (1994). Prevalence of mental disorders among children in Valencia, Spain. Acta Psychiatrica Scandinavica, 89: 352-357.
6Steinhausen HC et al. (1998). Prevalence of child and adolescent psychiatric disorders: the Zurich Epidemiological Study. Acta Psychiatrica Scandinavica, 98: 262-271.
7Shaffer D et al. (1996). The NIMH Diagnostic Interview Schedule for Children version 2.3 (DISC-2.3): description acceptability, prevalence rates, and performance in the MECA study. Journal of the American Academy of Child and Adolescent Psychiatry, 35: 865-877.

Mental and behavioural disorders of childhood and adolescence are very costly to society in both human and financial terms. The aggregate disease burden of these disorders has not been estimated, and it would be complex to calculate because many of these disorders can be precursors to much more disabling disorders during later life.

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