What Is Mental Illness and What Causes It?

Mental Illness
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Mental illness is a term used for any condition that affects a person's mood, behavior or thoughts in a way that is distressing or impairs functioning. Some sources still refer to mental illness in ways like "disease of the mind," a definition that promotes stigma. This type of attitude is more and more falling out of favor as researchers uncover the biological causes of mental illnesses.

The term "mental illness" is also used collectively to describe all mental disorders.

Thus, one could say, "Bipolar disorder is a mental illness," or "John has a mental illness," which could mean any recognized mental disorder.

In December 2006 a US District Court judge ruled that bipolar disorder is a physical illness for insurance purposes. Obviously, the biological causes of bipolar disorder affect the mind in terms of mood, thinking, and behavior. One could say that the physical illness causes the mental illness.

On the other hand, some people and organizations dispute the very existence of mental illness. For example, an organization called Fight for Kids defines "mental illness" as, "A sickness of the brain according to psychiatrists and psychologists, but for which there is no proof at all of its existence. This does not mean that problems don't exist, or that a person can never feel bad, but there is no evidence that these are caused by a sickness of the brain." Considering that there is substantial proof that mental illnesses such as bipolar disorder do exist and have biological causes, this kind of definition can only do harm to those who have mental disorders.


  • Albert has bipolar disorder, a mental illness that causes mood swings and sometimes affects his thinking and his behavior.
  • We now know that mental illness is, in many cases, caused by an underlying physical condition that affects the way the brain works.

WordNet Search. Mental Illness
The Science of Mental Illness. Glossary. National Institute of Mental Health
Fight for Kids. Glossary. Citizens Commission on Human Rights® International

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