Mental illness is common#
Mental illness is common. Around one in five adults experience a mental illness in any given year, and many people will be affected by mental illness at some point in their lives.
Mental illness is a general term for a group of illnesses that affect the brain. A mental illness is a health problem that significantly affects how a person feels, thinks, behaves and interacts with other people.
How mental illness is diagnosed and classified#
Mental illnesses are diagnosed according to standardized criteria. Their symptoms can interfere with people’s lives in different ways and to different degrees. Severity is often classified as mild, moderate or severe, based on the impact the symptoms have on a person’s home life, social life, ability to work and relationships.
Common types of mental illness#
The main groups of mental illness include:
- Mood disorders (also known as affective disorders), such as depression and bipolar disorder. Bipolar I disorder may affect up to 1% of people over their lifetime, and the lifetime risk of bipolar II disorder is up to about 5%.
- Anxiety disorders.
- Psychotic illness, such as schizophrenia.
Living with more than one mental illness#
Some people are affected by more than one mental illness at the same time. For example, a person living with an anxiety disorder may also experience depression.
Mental illness and the risk of suicide#
Mental illness is associated with an increased risk of suicide. Many people who die by suicide, or who experience suicidal thoughts, also have one or more other health conditions at the same time (sometimes called comorbidities), and a significant proportion of these are mental health conditions. Conditions commonly present alongside suicide and suicidal thoughts include mood disorders such as depression, anxiety and stress-related disorders, mental and behavioral disorders related to psychoactive drug use, and others.
Key points#
- Mental illness is common, affecting around one in five adults in any given year.
- Mental illness is a group of conditions that affect how a person feels, thinks, behaves and relates to others.
- Severity is classified as mild, moderate or severe based on the impact on daily life, work and relationships.
- The main types include mood disorders, anxiety disorders and psychotic illness, and some people live with more than one.
- Mental illness is associated with an increased risk of suicide.
Where to get help#
Sources & further reading
For evidence-based global guidance on this topic, consult authoritative public-health bodies such as the World Health Organization (WHO), CDC, NHS, and ECDC.