This article originally appeared in the July 2006 Harvard Mental Health Letter and is provided courtesy of Harvard Health Publications.

In Brief
Genetic counseling in psychiatry

Explaining genetic aspects of mental health problems is only a small part of psychiatric treatment, according to an article in the Harvard Review of Psychiatry, but scientific advances will increase both the demand for genetic counseling and the need to understand its uses and limitations.

Most psychiatric disorders, including major mental illness — schizophrenia, bipolar disorder, and major depression — are highly heritable. Family history is one of the best indicators of a person’s risk for mental illness. Naturally, patients and families want more detailed information. If they have overestimated the risk, they may be reassured. If they have underestimated the risk, they will be on notice.

American Psychiatric Association guidelines already endorse genetic counseling to aid family planning for people with bipolar disorder. Genetic information can also guide clinicians; for example, a patient undergoing a first episode of depression who has close relatives with bipolar disorder may be better off taking a mood stabilizer rather than a standard antidepressant.

A genetic counselor — psychiatrist or genetics expert — must learn as much as possible from family members, then estimate the risks, explain the results, test their understanding, and, if they wish, help them make decisions. Professionals can also take the opportunity to reassure parents that major mental illness is not their fault.

But given what we know, risk estimates are bound to be uncertain. For one thing, evidence may be hard to come by. Most family members cannot be examined, although it is sometimes possible to obtain medical records or consult clinicians who have treated them. Other obstacles also confront genetic counseling: Psychiatric symptoms are subjective, the symptoms of psychiatric disorders overlap, and the line between mental illness and normality can be blurry. Because of these ambiguities, it’s often doubtful who is at risk and how great the risk is.

Even if these problems are solved, estimating relative risks can be difficult. Knowing the rate of a psychiatric disorder in the general population is not enough; for example, the chance of developing bipolar disorder varies from 5% for a person who has one close relative with the disorder to more than 50% for a person who has four close relatives. The risk also depends on the age when symptoms first appear, among other things.

Most psychiatric disorders result from the interaction of many, usually unknown genes, each with small effects, in combination with various environmental influences that are also poorly understood. Whereas some illnesses with psychiatric symptoms such as Huntington’s disease are reliably linked with individual genes, to date psychiatric disorders are not. Family history is almost always a much better predictor of mental illness than any direct genetic test.

But there are some straws in the wind. One variant (allele) of a gene that regulates the flow of the neurotransmitter serotonin may raise the risk of becoming depressed under stress. Although the evidence is disputed, one variant of a gene that provides the recipe for an enzyme that metabolizes the neurotransmitter dopamine may raise the risk for schizophrenia. Vulnerability to Alzheimer’s disease is powerfully affected by a gene that codes for the production of apolipoprotein E, which helps transport cholesterol in the blood. If you carry one copy of the E4 variant of this gene, your risk for Alzheimer’s is tripled, and if you carry two copies, the risk is raised 15 times. But the value of testing is disputed because this allele is neither necessary nor sufficient for the development of Alzheimer’s, and because there is no way to cure or prevent the disease.

Despite the uncertainties, family members are increasingly interested in genetic testing. Although professionals are dubious, testing for Apo E4 seems to be in high demand. According to one survey, almost all people with bipolar disorder and their husbands and wives would definitely or probably take a genetic test for the disorder. In a survey of mental health support group members, medical students, and psychiatry residents, more than half would welcome and use a genetic test for bipolar disorder in children, even if there was no way to prevent the disorder.

As scientific advances allow more accurate identification of individual genetic risks, increasing numbers of people will be seeking this kind of help. But professionals with genetic expertise often have a poor understanding of psychiatric diagnoses, and psychiatrists and other clinicians (as they admit in surveys) know less about genetics than they think they should know. So better professional education will be needed to improve patient and family education about the genetics of psychiatric disorders.

Finn CT, et al. “Genetic Counseling in Psychiatry,” Harvard Review of Psychiatry (March–April 2006): Vol. 14, No. 2, pp. 109–21.