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Ask the Mental Health Expert Archives 2001-2004

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Chemical Imbalance

Q. I would like to find out exactly what a chemical imbalance is. Is it actually an imbalance of the chemicals of the brain or is it just a term used for a mentally unbalanced person? If it is an imbalance of the brain chemicals, how is it diagnosed? Are there specific medical tests done to diagnose it?

A. You are asking some very precise questions on a very imprecise issue! The term chemical imbalance, I'm afraid, is not a medical or psychiatric term in the strict sense. It is often used as a short-hand explanation for severe psychiatric disorders, such as schizophrenia, bipolar (manic-depressive) disorder, and panic disorder. However, that is certainly an over-simplification. All of these conditions-while very strongly driven by biochemical and genetic factors-also have a psychological and social dimension.

Nevertheless, we do have good, though mostly indirect, evidence that these disorders do have specific biochemical abnormalities associated with them. For example, there are several lines of evidence showing that the brain chemical dopamine is involved in schizophrenia. Several studies of schizophrenia suggest that dopamine is too plentiful in certain brain regions, and not plentiful enough in others. Similarly, major depression has been linked with abnormal levels of serotonin, another brain chemical that influences mood, appetite, sleep, sexuality, and many other functions.

Panic disorder has been linked with abnormalities in yet another brain chemical, norepinephrine. The kinds of studies that yield this evidence are very sophisticated, and are usually carried out only in academic research settings-they are neither necessary nor sufficient to make the diagnosis of a mental disorder. That remains a clinical determination, based on the patient's personal and family history, mental state, and symptoms.

On the other hand, certain readily available tests-such as those for abnormal thyroid function-can sometimes reveal a biochemical cause for a person's psychiatric symptoms. For example, very low thyroid function can often provoke depression. Since thyroid hormone is taken up by the brain, this would be an example of an imbalance in brain chemicals that can cause psychiatric symptoms. The same might be true of a vitamin B12 deficiency.

Unfortunately, most major mental disorders have not yet been linked convincingly with such specific biochemical problems. Someday, perhaps we will have a lab test for these major disorders-but not yet. If you wish to read more about the biochemical bases of psychiatric disorders, you might want to see the book "Depression: How It Happens, How Its Healed", by Dr. John Medina. For more specific information on research studies, you can contact the National Alliance for Research on Schizophrenia and Depression (516-829-0091).

February 2001

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