Difference between Mental Illness and Mental Disorder

"Mental Illness" and "mental disorder" are typically used interchangeably. However, there has, historically, been a difference between mental illness and mental disorders.

What Are Mental Disorders?

According to The American Heritage Stedman's Medical Dictionary, the following is the definition of "disorder" in medicine:

disorder dis·or·der (dĭs-ôr'dər) n. - A disturbance or derangement that affects the function of mind or body, such as an eating disorder or the abuse of a drug.

dis·or·dered , dis·or·der·ing , dis·or·ders v. - To disturb the normal physical or mental health of; derange.

Because the definition of "disorder" includes, specifically, a disturbance of the mind (such as a mental disorder) it better fits what we now call mental illnesses, particularly before we understood that mental disorders are truly disorders of the brain (and not simply the "mind").

What Are Mental Illnesses?

According to The American Heritage Stedman's Medical Dictionary, the following is the definition of "illness" in medicine:

disease dis·ease (dĭ-zēz') n. - A pathological condition of a body part, an organ, or a system resulting from various causes, such as infection, genetic defect, or environmental stress, and characterized by an identifiable group of signs or symptoms.

Because "disease" specifies that the pathological condition be of a body part, people were less likely to use the term "mental illness" before it was understood that mental illness are diseases of the body.

The difference between "mental disorder" and "mental illness," then is one of considering the origin of the condition.

List of Mental Illnesses, Disorders

The major types of mental illnesses, disorders are the following:

• Acute Stress Disorder
• Agoraphobia (anxiety about being in places where escape might not be possible)
• Amnesia, Dissociative
• Anorexia Nervosa
• Attention Deficit/Hyperactivity Disorder (ADHD)
• Bipolar Disorder
• Body Dysmorphic Disorder (preoccupation with a specific body part or parts and believing it or them is defective)
• Brief Psychotic Disorder
• Bulimia Nervosa
• Conversion Disorder (deficits in voluntary motor or sensory functions which are not intentionally produced but cannot be better explained by another health condition (such as mutism))
• Cyclothymic Disorder (a more mild variant of bipolar disorder)
• Delusional Disorder
• Depersonalization Disorder (feelings of unreality, that your body does not belong to you, or that you are constantly in a dreamlike state)
• Dissociative Identity Disorder (DID)
• Dyspareunia (recurrent or persistent genital pain associated with sexual intercourse not better explained by substance abuse or another medical condition)
• Dysthymic Disorder (depressed mood for most of the day on most days for more than two years)
• Erectile Disorder, Male
• Exhibitionism
• Fetishism
• Frotteurism (either intense sexually arousing fantasies, urges, or behaviors in which the individual touches or rubs against a non-consenting person in a sexual manner)
• Gambling, Pathological
• Gender Identity Disorder
• Generalized Anxiety Disorder
• Hypoactive Sexual Desire Disorder
• Hypochondriasis (preoccupation with fears of having a serious disease based upon a misinterpretation of bodily sensations)
• Impotence
• Intermittent Explosive Disorder
• Kleptomania
• Masochism, Sexual
• Major Depressive Disorder
• Obsessive-Compulsive Disorder
• Orgasmic Disorder, Female
• Orgasmic Disorder, Male
• Pain Disorder
• Panic Disorder
• Pedophilia
• Phobias
• Posttraumatic Stress Disorder
• Premature Ejaculation
• Pyromania
• Sadism, Sexual
• Schizophrenia
• Schizoaffective Disorder (a combination of schizophrenia and an affective disorder such as depression or bipolar disorder)
• Schizophreniform (a tentative diagnosis typically used before the diagnosis of schizophrenia)
• Sexual Arousal Disorder, Female
• Sexual Aversion Disorder
• Shared Psychotic
• Somatization Disorder (a history of physical complaints before the age of 30 not better explained by another medical condition)
• Substance Abuse
• Transvestic Fetishism
• Trichotillomania (recurrent pulling out of one's own hair)
• Vaginismus (recurrent or persistent involuntary spasm of the vaginal muscles that interferes with sexual intercourse not better explained by another medical condition)
• Voyeurism