Mental health is the emotional, psychological, and social dimension of health. It concerns how people experience emotions, think, relate to others, and function in everyday life. The World Health Organization describes it in terms of well-being, coping with life’s stresses, developing abilities, learning, working, and participating in community life. Mental health is more than the absence of illness: people with diagnosed conditions may experience positive well-being, while people without a diagnosis may experience substantial distress. (who.int)
Well-being, distress, and mental disorders
Mental health exists on a continuum rather than as a simple division between healthy and unhealthy states. Emotional well-being includes managing emotions, maintaining supportive relationships, and experiencing meaning or purpose. Psychological distress refers to experiences such as mental anguish, perceived lack of control, anxiety, or stress. Distress and a diagnosable disorder are related but are not interchangeable concepts. (who.int)
A mental disorder involves a clinically significant disturbance in cognition, emotional regulation, or behavior, usually associated with distress or impaired functioning. Conditions include depression, anxiety disorders, bipolar disorder, schizophrenia, eating disorders, and post-traumatic stress disorder. They differ in symptoms, duration, severity, and course; more than one condition can occur in the same person. Mental health conditions are a broader category that also encompasses psychosocial disabilities and other states associated with significant distress or functional impairment. (who.int)
Determinants across the life course
There is no single cause of mental health conditions. Individual characteristics, biological vulnerability, experiences, relationships, and environmental circumstances interact over time. Genetics, substance use, and emotional skills can influence vulnerability, but no individual factor reliably predicts a person’s mental health outcome. Exposure to a risk factor does not necessarily result in illness. (who.int)
The social determinants of health include the circumstances in which people live, learn, and work. Poverty, violence, inequality, and adverse living conditions can increase mental health risks. Protective circumstances include supportive interactions, access to quality education, safe neighborhoods, and community connections. Early childhood and adolescence are particularly important developmental periods because adverse experiences can have lasting effects. (who.int)
During adolescence, physical, emotional, and social changes interact with pressures involving identity, peer relationships, and home circumstances. WHO identifies supportive family, school, and community environments as important to adolescent mental well-being. Exposure to abuse, bullying, discrimination, or exclusion can increase vulnerability. These influences make adolescent mental health relevant to education and child-protection services as well as clinical care. (who.int)
Relationship with physical health
Mental and physical health are closely connected. Depression is associated with increased risk of several chronic physical conditions, while living with chronic illness can increase the risk of mental health difficulties. Changes in mood, concentration, sleep, or appetite may also arise from physical medical conditions, which is one reason clinical assessment considers both mental and physical health. Mental health care therefore intersects with general medicine, rather than forming an entirely separate sphere of health. (cdc.gov)
Assessment and classification
Clinical diagnosis uses defined requirements to distinguish disorders and guide care. The International Classification of Diseases provides an international framework for recording and reporting health conditions. WHO published its ICD-11 clinical descriptions and diagnostic requirements for mental, behavioral, and neurodevelopmental disorders in March 2024. This manual supports consistent identification in clinical settings and was developed through evidence review and international clinical testing. (who.int)
Population-level epidemiology addresses a different question: how frequently conditions occur and how their distribution varies. WHO’s September 2026 fact sheet reports that approximately 1.2 billion people—nearly one in seven worldwide—were living with a mental disorder in 2023. Anxiety and depressive disorders were the most common. The estimate concerns mental disorders, not every form of distress or reduced well-being. (who.int)
Treatment and support
Psychotherapy comprises treatments intended to help people identify and change troubling emotions, thoughts, and behaviors. Its goals can include symptom relief, improved daily functioning, and better quality of life. It may take place individually or in groups. Cognitive behavioral therapy is one established approach; evidence for a particular therapy depends on the condition and treatment studied. (nimh.nih.gov)
Medications are another major treatment category. They include antidepressants, antipsychotics, and mood stabilizers, with different indications and potential adverse effects. Responses vary between individuals, and medication may be combined with psychotherapy. Brain-stimulation treatments are used for selected conditions, including some cases that have not responded to other treatments. These interventions address particular clinical needs rather than defining mental health itself. (nimh.nih.gov)
Public health and service organization
Public health approaches address population conditions alongside individual treatment. Health promotion and prevention initiatives operate in schools, workplaces, and communities. During humanitarian emergencies, psychological distress is widespread, although most affected people do not develop a mental disorder; responses include community support and clinical services for those with specific needs. (cdc.gov)
Within a health system, mental health services can include primary health care, general hospitals, specialist community teams, peer support, supported living, and psychosocial rehabilitation. WHO’s service framework emphasizes accessible community-based care and protection of human rights. Availability and coverage remain uneven, with substantial gaps between the need for care and access to services. (who.int)