Difference between Mental Illness and Personality Disorder

There is no agreement among the professional psychiatrists as to what mental illness is. Sometimes a term “personality disorder” is applied to a mental illness, and vice versa, depending on a type of disorder and the specific case. We will explore the differences between mental illness and personality disorder further in this article.


Mental Illness vs Personality Disorder
A picture by Armand Gautier, showing people with commonly diagnosed mental illnesses in the 19th century

A mental illness can be defined in general terms as the illness of the human mind. Mental illnesses have been registered since Ancient times and have become a source of great controversies both in society and among professional psychologists and psychiatrists. A mentally ill individual possesses the set of traits that are at odds with what is common in a given society. Mental illnesses manifest themselves in  antisocial behavior, violence or otherwise inappropriate recurring actions. A mental illness is often accompanied by changes in the brain of the sufferer. For example, a person diagnosed with schizophrenia usually has impairment in the cortex regions of the brain that are responsible for cognitive skills.

A personality disorder is characterized by long lasting patterns of behavior of the individual that are considered deviant in the given society. However, a person with a personality disorder may lead a perfectly normal life as long as the personality disorder doesn’t manifest itself in harmful behavior. The list of personality disorders is long and is sited in the two chief classifications – The Diagnostic and Statistical Manual of Mental Disorders (DSM) and The International Statistical Classification of Diseases and Related Health Problems (ICD). The two lists differ as far as some of the personality disorders are concerned, and are always in the process of revision and addition.

Comparison chart

Mental Illness Personality Disorder
A mental illness is characterized by the extremity of the traits A personality disorder is characterized by the moderate character of the traits
A mental illness can develop in a relatively short time Personality disorders are characterized by lifelong patterns
Mental illness and physical illness are comparable A personality disorder can’t be compared to a physical illness

Mental Illness vs Personality Disorder

What is the difference between Mental Illness and Personality Disorder?

  • A mental illness is about extremity. A personality disorder, on the other hand, is sometimes a precursor to a mental illness. The traits that are characteristic for a certain personality disorder may develop at some point to their extreme; and if they do, a personality disorder becomes a mental illness. For example, people with schizopathic personality disorder may develop a mental illness called schizophrenia, if and when the traits of a schizopathic disorder such as social withdrawal and hallucinations get to the point when a person cannot control them. Personality disorders in general can be regarded as risk factors for mental disorders.
  • Personality disorders usually feature a number of patterns that are present in the course of the entire life of a person. Usually the signs and the symptoms of personality disorders can be spotted in early childhood.  Mental illnesses, on the other hand, can manifest themselves at any point during the life of a person and are usually not diagnosed earlier than during one’s twenties.
  • A mental illness can be as heavy as a serious physical illness. A mental illness often has a biomedical cause and requires  hospitalization or  total control over a patient. A mental illness also requires  treatment with medication. A personality disorder, on the other hand, cannot be compared to a physical illness. Personality disorders rarely have biomedical cause.  A person suffering from a personality disorder leads a seemingly normal life and usually doesn’t need medications.