A mental illness is a condition that affects a person’s thinking, feeling or mood. Such conditions may affect someone’s ability to relate to others and function each day. Each person will have experiences that differ, even if they share the same diagnosis.

A mental health condition isn’t the result of one event. Research suggests multiple, linking causes. Genetics, environment and lifestyle influence whether someone develops a mental health condition. A stressful job or home life makes some people more susceptible, as do traumatic life events like being the victim of a crime. Biochemical processes and circuits and basic brain structure may play a role too.