Other, less common types of mental illnesses include:

Stress response syndromes (formerly called adjustment disorders): Stress response syndromes occur when a person develops emotional or behavioral symptoms in response to a stressful event or situation. The stressors may include natural disasters, such as an earthquake or tornado; events or crises, such as a car accident or the diagnosis of a major illness; or interpersonal problems, such as a divorce, death of a loved one, loss of a job, or a problem with substance abuse. Stress response syndromes usually begin within three months of the event or situation and ends within six months after the stressor stops or is eliminated.

Stress response syndromes occur when a person develops emotional or behavioral symptoms in response to a stressful event or situation. The stressors may include natural disasters, such as an earthquake or tornado; events or crises, such as a car accident or the diagnosis of a major illness; or interpersonal problems, such as a divorce, death of a loved one, loss of a job, or a problem with substance abuse. Stress response syndromes usually begin within three months of the event or situation and ends within six months after the stressor stops or is eliminated. Dissociative disorders: People with these disorders suffer severe disturbances or changes in memory, consciousness, identity, and general awareness of themselves and their surroundings. These disorders usually are associated with overwhelming stress, which may be the result of traumatic events, accidents, or disasters that may be experienced or witnessed by the individual. Dissociative identity disorder, formerly called multiple personality disorder, or "split personality," and depersonalization disorder are examples of dissociative disorders.

People with these disorders suffer severe disturbances or changes in memory, consciousness, identity, and general awareness of themselves and their surroundings. These disorders usually are associated with overwhelming stress, which may be the result of traumatic events, accidents, or disasters that may be experienced or witnessed by the individual. Dissociative identity disorder, formerly called multiple personality disorder, or "split personality," and depersonalization disorder are examples of dissociative disorders. Factitious disorders: Factitious disorders are conditions in which a person knowingly and intentionally creates or complains of physical and/or emotional symptoms in order to place the individual in the role of a patient or a person in need of help.

Factitious disorders are conditions in which a person knowingly and intentionally creates or complains of physical and/or emotional symptoms in order to place the individual in the role of a patient or a person in need of help. Sexual and gender disorders: These include disorders that affect sexual desire, performance, and behavior. Sexual dysfunction, gender identity disorder, and the paraphilias are examples of sexual and gender disorders.

These include disorders that affect sexual desire, performance, and behavior. Sexual dysfunction, gender identity disorder, and the paraphilias are examples of sexual and gender disorders. Somatic symptom disorders: A person with a somatic symptom disorder, formerly known as a psychosomatic disorder or somatoform disorder, experiences physical symptoms of an illness or of pain with an excessive and disproportionate level of distress, regardless of whether or not a doctor can find a medical cause for the symptoms.

A person with a somatic symptom disorder, formerly known as a psychosomatic disorder or somatoform disorder, experiences physical symptoms of an illness or of pain with an excessive and disproportionate level of distress, regardless of whether or not a doctor can find a medical cause for the symptoms. Tic disorders: People with tic disorders make sounds or display nonpurposeful body movements that are repeated, quick, sudden, and/or uncontrollable. (Sounds that are made involuntarily are called vocal tics.) Tourette's syndrome is an example of a tic disorder.

Other diseases or conditions, including various sleep-related problems and many forms of dementia, including Alzheimer's disease, are sometimes classified as mental illnesses, because they involve the brain.