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Mental disorders

Fact sheet
Reviewed April 2017

Key facts

  • There are many different mental disorders, with different presentations. They are generally characterized by a combination of abnormal thoughts, perceptions, emotions, behaviour and relationships with others.
  • Mental disorders include: depression, bipolar affective disorder, schizophrenia and other psychoses, dementia, intellectual disabilities and developmental disorders including autism.
  • There are effective strategies for preventing mental disorders such as depression.
  • There are effective treatments for mental disorders and ways to alleviate the suffering caused by them.
  • Access to health care and social services capable of providing treatment and social support is key.

The burden of mental disorders continues to grow with significant impacts on health and major social, human rights and economic consequences in all countries of the world.


Depression is a common mental disorder and one of the main causes of disability worldwide. Globally, an estimated 300 million people are affected by depression. More women are affected than men.

Depression is characterized by sadness, loss of interest or pleasure, feelings of guilt or low self-worth, disturbed sleep or appetite, tiredness, and poor concentration. Sufferers may also have multiple physical complaints with no apparent physical cause. Depression can be long-lasting or recurrent, substantially impairing people’s ability to function at work or school and to cope with daily life. At its most severe, depression can lead to suicide.

Prevention programmes have been shown to reduce depression, both for children (e.g. through protection and psychological support following physical and sexual abuse) and adults (e.g. through psychosocial assistance after disasters and conflicts).

There are also effective treatments. Mild to moderate depression can be effectively treated with talking therapies, such as cognitive behaviour therapy or psychotherapy. Antidepressants can be an effective form of treatment for moderate to severe depression but are not the first line of treatment for cases of mild depression. They should not be used for treating depression in children and are not the first line of treatment in adolescents, among whom they should be used with caution.

Management of depression has to include psychosocial aspects, including identifying stress factors, such as financial problems, difficulties at work or physical or mental abuse, and sources of support, such as family members and friends. The maintenance or reactivation of social networks and social activities is important.

Bipolar affective disorder

This disorder affects about 60 million people worldwide. It typically consists of both manic and depressive episodes separated by periods of normal mood. Manic episodes involve elevated or irritable mood, over-activity, pressure of speech, inflated self-esteem and a decreased need for sleep. People who have manic attacks but do not experience depressive episodes are also classified as having bipolar disorder.

Effective treatments are available for the treatment of the acute phase of bipolar disorder and the prevention of relapse. These are medicines that stabilize mood. Psychosocial support is an important component of treatment.

Schizophrenia and other psychoses

Schizophrenia is a severe mental disorder, affecting about 21 million people worldwide. Psychoses, including schizophrenia, are characterized by distortions in thinking, perception, emotions, language, sense of self and behaviour. Common psychotic experiences include hallucinations (hearing, seeing or feeling things that are not there) and delusions( fixed false beliefs or suspicions that are firmly held even when there is evidence to the contrary). The disorder can make it difficult for people affected to work or study normally.

Stigma and discrimination can result in a lack of access to health and social services. Furthermore, people with psychosis are at high risk of exposure to human rights violations, such as long term confinement in institutions.

Schizophrenia typically begins in late adolescence or early adulthood. Treatment with medicines and psychosocial support is effective. With appropriate treatment and social support, affected people can lead a productive life, be integrated in society. Facilitation of assisted living, supported housing and supported employment can act as a base from which people with severe mental disorders, including Schizophrenia, can achieve numerous recovery goals as they often face difficulty in obtaining or retaining normal employment or housing opportunities..


Worldwide, 47.5 million people have dementia. Dementia is usually of a chronic or progressive nature in which there is deterioration in cognitive function (i.e. the ability to process thought) beyond what might be expected from normal ageing. It affects memory, thinking, orientation, comprehension, calculation, learning capacity, language, and judgement. The impairment in cognitive function is commonly accompanied, and occasionally preceded, by deterioration in emotional control, social behaviour, or motivation.

Dementia is caused by a variety of diseases and injuries that affect the brain, such as Alzheimer's disease or stroke.

Though there is no treatment currently available to cure dementia or to alter its progressive course, many treatments are in various stages of clinical trials. Much can be done, however, to support and improve both the lives of people with dementia and their caregivers and families.

Developmental disorders, including autism

Developmental disorder is an umbrella term covering intellectual disability and pervasive developmental disorders including autism. Developmental disorders usually have a childhood onset but tend to persist into adulthood, causing impairment or delay in functions related to the central nervous system maturation. They generally follow a steady course rather than the periods of remissions and relapses that characterize many other mental disorders.

Intellectual disability is characterized by impairment of skills across multiple developmental area such as cognitive functioning and adaptive behaviour. Lower intelligence diminishes the ability to adapt to the daily demands of life.

Symptoms of pervasive developmental disorders, such as autism, include impaired social behaviour, communication and language, and a narrow range of interests and activities that are both unique to the individual and are carried out repetitively. Developmental disorders often originate in infancy or early childhood. People with these disorders occasionally display some degree of intellectual disability.

Family involvement in care of people with developmental disorders is very important. Knowing what causes affected people both distress and wellbeing is an important element of care, as is finding out what environments are most conductive to better learning. Structure to daily routines help prevent unnecessary stress, with regular times for eating, playing, learning, being with others, and sleeping. Regular follow up by health services of both children and adults with developmental disorders, and their carers, needs to be in place.

The community at large has a role to play in respecting the rights and needs of people with disabilities.

Who is at risk from mental disorders?

Determinants of mental health and mental disorders include not only individual attributes such as the ability to manage one's thoughts, emotions, behaviours and interactions with others, but also social, cultural, economic, political and environmental factors such as national policies, social protection, standards of living, working conditions, and community support.

Stress, Genetics, nutrition, perinatal infections and exposure to environmental hazards are also contributing factors to mental disorders.

Health and support

Health systems have not yet adequately responded to the burden of mental disorders. As a consequence, the gap between the need for treatment and its provision is wide all over the world. In low- and middle-income countries, between 76% and 85% of people with mental disorders receive no treatment for their disorder. In high-income countries, between 35% and 50% of people with mental disorders are in the same situation.

A further compounding problem is the poor quality of care for many of those who do receive treatment.

In addition to support from health-care services, people with mental illness require social support and care. They often need help in accessing educational programmes which fit their needs, and in finding employment and housing which enable them to live and be active in their local communities.

WHO response

WHO’s Mental Health Action Plan 2013-2020, endorsed by the World Health Assembly in 2013, recognizes the essential role of mental health in achieving health for all people. The plan includes 4 major objectives:

  • more effective leadership and governance for mental health;
  • the implementation of strategies for promotion and prevention; and
  • strengthened information systems, evidence and research.

WHO's Mental Health Gap Action Programme (mhGAP), launched in 2008, uses evidence-based technical guidance, tools and training packages to expand service in countries, especially in resource-poor settings. It focuses on a prioritized set of conditions, directing capacity building towards non-specialized health-care providers in an integrated approach that promotes mental health at all levels of care.