According to the U.S. surgeon general, mental health is the successful performance of mental function, resulting in productive activities, fulfilling relationships with other people, and providing the ability to adapt to change and cope with adversity.

The term mental illness refers collectively to all diagnosable mental disorders—health conditions characterized by alterations in thinking, mood, or behavior associated with distress or impaired functioning.

A person struggling with his or her mental health may experience stress, depression, anxiety, relationship problems, grief, addiction, ADHD or learning disabilities, mood disorders, or other mental illnesses of varying degrees. Therapists, psychiatrists, psychologists, social workers, nurse practitioners or physicians can help manage mental illness with treatments such as therapy, counseling, or medication.

Mental illnesses are categorized as follows:

Neurosis: Also known as psychoneuroses, neuroses are minor mental illnesses like phobias, obsessive-compulsive disorders, and anxiety disorders, among others.

Psychosis: Psychoses are major mental illnesses in which the mental state impairs thoughts, perception and judgement. Delusions and hallucinations are marked symptoms. This may require the use of psychotic drugs as well as counselling techniques in order to treat them.