2 CME Credits

Key Facts

Mental disorders

Key facts

  • 1 in every 8 people in the world live with a mental disorder
  • Mental disorders involve significant disturbances in thinking, emotional regulation, or behavior
  • There are many different types of mental disorders
  • Effective prevention and treatment options exist
  • Most people do not have access to effective care

A mental disorder is characterized by a clinically significant disturbance in an individual’s cognition, emotional regulation, or behavior. It is usually associated with distress or impairment in important areas of functioning. There are many different types of mental disorders. Mental disorders may also be referred to as mental health conditions. The latter is a broader term covering mental disorders, psychosocial disabilities and (other) mental states associated with significant distress, impairment in functioning, or risk of self-harm. This fact sheet focuses on mental disorders as described by the International Classification of Diseases 11th Revision (ICD-11).

In 2019, 1 in every 8 people, or 970 million people around the world were living with a mental disorder, with anxiety and depressive disorders the most common (1). In 2020, the number of people living with anxiety and depressive disorders rose significantly because of the COVID-19 pandemic. Initial estimates show a 26% and 28% increase respectively for anxiety and major depressive disorders in just one year (2). While effective prevention and treatment options exist, most people with mental disorders do not have access to effective care. Many people also experience stigma, discrimination and violations of human rights.

Anxiety Disorders

In 2019, 301 million people were living with an anxiety disorder including 58 million children and adolescents (1). Anxiety disorders are characterized by excessive fear and worry and related behavioral disturbances. Symptoms are severe enough to result in significant distress or significant impairment in functioning. There are several different kinds of anxiety disorders, such as: generalized anxiety disorder (characterized by excessive worry), panic disorder (characterized by panic attacks), social anxiety disorder (characterized by excessive fear and worry in social situations), separation anxiety disorder (characterized by excessive fear or anxiety about separation from those individuals to whom the person has a deep emotional bond), and others. Effective psychological treatment exists, and depending on the age and severity, medication may also be considered.


In 2019, 280 million people were living with depression, including 23 million children and adolescents (1). Depression is different from usual mood fluctuations and short-lived emotional responses to challenges in everyday life. During a depressive episode, the person experiences depressed mood (feeling sad, irritable, empty) or a loss of pleasure or interest in activities, for most of the day, nearly every day, for at least two weeks. Several other symptoms are also present, which may include poor concentration, feelings of excessive guilt or low self-worth, hopelessness about the future, thoughts about dying or suicide, disrupted sleep, changes in appetite or weight, and feeling especially tired or low in energy. People with depression are at an increased risk of suicide. Yet, effective psychological treatment exists, and depending on the age and severity, medication may also be considered.

Bipolar Disorder

In 2019, 40 million people experienced bipolar disorder (1). People with bipolar disorder experience alternating depressive episodes with periods of manic symptoms. During a depressive episode, the person experiences depressed mood (feeling sad, irritable, empty) or a loss of pleasure or interest in activities, for most of the day, nearly every day. Manic symptoms may include euphoria or irritability, increased activity or energy, and other symptoms such as increased talkativeness, racing thoughts, increased self-esteem, decreased need for sleep, distractibility, and impulsive reckless behavior. People with bipolar disorder are at an increased risk of suicide. Yet effective treatment options exist including psycho education, reduction of stress and strengthening of social functioning, and medication.

Post-Traumatic Stress Disorder (PTSD)

The prevalence of PTSD and other mental disorders is high in conflict-affected settings (3). PTSD may develop following exposure to an extremely threatening or horrific event or series of events. It is characterized by all of the following: 1) re-experiencing the traumatic event or events in the present (intrusive memories, flashbacks, or nightmares); 2) avoidance of thoughts and memories of the event(s), or avoidance of activities, situations, or people reminiscent of the event(s); and 3) persistent perceptions of heightened current threat. These symptoms persist for at least several weeks and cause significant impairment in functioning. Effective psychological treatment exists.


Schizophrenia affects approximately 24 million people or 1 in 300 people worldwide (1). People with schizophrenia have a life expectancy 10-20 years below that of the general population (4). Schizophrenia is characterized by significant impairments in perception and changes in behavior. Symptoms may include persistent delusions, hallucinations, disorganized thinking, highly disorganized behavior, or extreme agitation. People with schizophrenia may experience persistent difficulties with their cognitive functioning. Yet, a range of effective treatment options exist, including medication, psycho education, family interventions, and psychosocial rehabilitation.

Eating Disorders

In 2019, 14 million people experienced eating disorders including almost 3 million children and adolescents (1). Eating disorders, such as anorexia nervosa and bulimia nervosa, involve abnormal eating and preoccupation with food as well as prominent body weight and shape concerns. The symptoms or behaviors result in significant risk or damage to health, significant distress, or significant impairment of functioning. Anorexia nervosa often has its onset during adolescence or early adulthood and is associated with premature death due to medical complications or suicide. Individuals with bulimia nervosa are at a significantly increased risk for substance use, suicidality, and health complications. Effective treatment options exist, including family-based treatment and cognitive-based therapy.

Disruptive behavior and dissocial disorders

40 million people, including children and adolescents, were living with conduct-dissocial disorder in 2019 (1). This disorder, also known as conduct disorder, is one of two disruptive behavior and dissocial disorders, the other is oppositional defiant disorder. Disruptive behavior and dissocial disorders are characterized by persistent behavior problems such as persistently defiant or disobedient to behaviors that persistently violate the basic rights of others or major age-appropriate societal norms, rules, or laws. Onset of disruptive and dissocial disorders, is commonly, though not always, during childhood. Effective psychological treatments exist, often involving parents, caregivers, and teachers, cognitive problem-solving or social skills training.

Neurodevelop mental disorders

Neurodevelopmental disorders are behavioral and cognitive disorders, that? arise during the developmental period, and involve significant difficulties in the acquisition and execution of specific intellectual, motor, language, or social functions.

Neurodevelopmental disorders include disorders of intellectual development, autism spectrum disorder, and attention deficit hyperactivity disorder (ADHD) amongst others. ADHD is characterized by a persistent pattern of inattention and/or hyperactivity-impulsivity that has a direct negative impact on academic, occupational, or social functioning. Disorders of intellectual development are characterized by significant limitations in intellectual functioning and adaptive behavior, which refers to difficulties with everyday conceptual, social, and practical skills that are performed in daily life. Autism spectrum disorder (ASD) constitutes a diverse group of conditions characterized by some degree of difficulty with social communication and reciprocal social interaction, as well as persistent restricted, repetitive, and inflexible patterns of behavior, interests, or activities.

Effective treatment options exist including psychosocial interventions, behavioral interventions, occupational and speech therapy. For certain diagnoses and age groups, medication may also be considered.

Who is at risk from developing a mental disorder?

At any one time, a diverse set of individual, family, community, and structural factors may combine to protect or undermine mental health. Although most people are resilient, people who are exposed to adverse circumstances – including poverty, violence, disability, and inequality – are at higher risk. Protective and risk factors include individual psychological and biological factors, such as emotional skills as well as genetics.Many of the risk and protective factors are influenced through changes in brain structure and/or function.

Health systems and social support

Health systems have not yet adequately responded to the needs of people with mental disorders and are significantly under resourced. The gap between the need for treatment and its provision is wide all over the world; and is often poor in quality when delivered. For example, only 29% of people with psychosis (5) and only one third of people with depression receive formal mental health care (6).

People with mental disorders also require social support, including support in developing and maintaining personal, family, and social relationships. People with mental disorders may also need support for educational programmes, employment, housing, and participation in other meaningful activities.

WHO response

WHO’s Comprehensive Mental Health Action Plan 2013-2030 recognizes the essential role of mental health in achieving health for all people. The plan includes 4 major objectives:

  • To strengthen effective leadership and governance for mental health;
  • To provide comprehensive, integrated and responsive mental health and social care services in community-based settings;
  • To implement of strategies for promotion and prevention in mental health; and
  • To strengthen information systems, evidence, and research for mental health.

WHO's Mental Health Gap Action Programme (mhGAP) uses evidence-based technical guidance, tools and training packages to expand services 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. The WHO mhGAP Intervention Guide 2.0 is part of this Programme, and provides guidance for doctors, nurses, and other health workers in non-specialist health settings on assessment and management of mental disorders.