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What is "abnormal"?
Types of Disorders
Anxiety Disorders
Mood Disorders
Personality Disorders
Delusional Disorder
Sexual Disorders
Somatoform & Dissociative

The medical perspective, also known as the biological perspective, is the belief that all, or atleast most, abnormal behavior can be traced to medical factors, usually affecting the brain in some way.1 This model assumes that all psychological disorders are diseases.2p The onset, distribution, course, treatment, and all related features of disorders can then be viewed as parallel to what occurs in physical diseases. Possible causes of mental illness from the biological perspective are genetics, neuroanatomy, chemical imbalance, and infection.1

Those who embrace the medical perspective approach mental illness in the same basic way. First, the patient is found to have a syndrome, which is a collection of symptoms that seem to occur at the same time. Once the syndrome has been identified, the etiological phase begins, where a cause is sought. The four possible causes listed above are then considered. Once etiology is established, then a way of preventing the illness, especially if it appears to be untreatable, or methods of treatment for those who already have the illness, are then sought out.


There are three principal methods used in studying the nature of genetic influence on abnormal behavior: family studies, twin studies, and adoptee studies.

Family Studies

In the past century there has been a huge advancement in genetic studies. Scientists can now approximate the common genes between family members of varrying closeness. A researcher can then look at the family members of a patient diagnosed with a mental illness and look for other family members who show signs of the same mental illness. When it is found that members of the same family tend to have a certain disease, other factors being equal, then a hereditary influence is suggested.

Twin Studies

The scientific reasoning behind twin studies is better than in family studies because monozygotic twins (identical twins) have exactly the same genes, and therefore their mental characteristics should be almost identical. Identical twins can be studied where atleast one is suffering from a mental illness and the concordance rate (percentage of times both twins are found to have the same illness) examined. Higher concordance rates than that of fraternal twins provides a strong argument for an hereditary effect on that illness.

Adoptee Studies

When identical twins are separated by adoption, their environmental factors are different, so the only thing that would most likely cause the same illness in both would be heredity. When the concordance rate is still found to be high in these studies, an even stronger argument for hereditary influence is built.


It has long been known that mental symptoms associated with aging--particularly memory loss and difficulty coping with new situations--results from changes in higher parts of the brain.1 This is an example of a defect in the anatomy of the brain, causing symptoms of mental illness.

Chemical Imbalance

The excess or deficiency of one or more chemical elements of the body has been studied as a cause of mental illness. For example, research suggests that schizophrenics have excess dopamine (a neurotransmitter) in the brain. Evidence for this is the fact that some of the symptoms of schizophrenia are reduced when patients are treated with drugs which reduce the amount of dopamine usable by the brain.


The first mental illness to be associated with infection was paresis, which is now recognized as the result of a long term infection by syphilis spirochete.1

1999 Katrina Spoor