Five mental health disorders may be more alike than they seem -- at a genetic level. That's the conclusion of a study published February 28. Researchers from 19 countries took part. Together, they analyzed the genomes -- the total genetic code -- of more than 61,000 people. Some of them had autism, attention-deficit hyperactivity disorder, bipolar disorder, major depression or schizophrenia. Others did not have any of these conditions. Variations in 4 areas of the genetic code were linked to all 5 disorders. Researchers cited 2 specific genes as a special concern. These genes regulate the flow of calcium in brain cells. This is a key part of how neurons signal each other. Researchers suggested that changes in genes could be one way that people become more vulnerable to these disorders. Usually, more than one change would have to occur for someone to develop a condition, they said. The journal Lancet published the study. The Associated Press wrote about it.

By Howard LeWine, M.D.
Harvard Medical School

What Is the Doctor's Reaction?

For a long time, psychiatrists have known that some of the major mental health conditions run in families. This is especially true for:

• Bipolar disorder
• Major depression
• Schizophrenia

Having a mother, father, sister or brother with one of these conditions increases your risk for that condition. And it also increases your risk of developing either of the other two conditions.

Sometimes several members of a family have psychiatric conditions. But it is very difficult to give the other family members an idea of their personal risk. That's because psychiatric conditions are diagnosed clinically. This means the doctor makes the diagnosis based on a set of symptoms. No tests, including genetic tests, can confirm a specific diagnosis.

However, symptoms between conditions overlap. So the diagnosis might not be straightforward.

Scientists are making progress in finding genes linked with certain mental health conditions. But this is no easy task.

Some diseases of the body have very distinct patterns of inheritance. For example, the child of a parent with Huntington's disease always has a 50% chance of inheriting the faulty gene. But for psychiatric diseases, many genes appear to be involved. Inheriting one or two of these genes only means you might have an increased risk.

A new study has moved us a step closer to finding inheritance patterns. The research was done by members of the Cross-Disorder Group of the Psychiatric Genetics Consortium. Their discovery will lead to new models of why a person develops psychiatric diseases.

The study found that four genetic variations are closely linked with three different clinical diagnoses:

• Bipolar disorder
• Major depression
• Schizophrenia

These same genes were also linked with autism spectrum disorder and ADHD (attention-deficit hyperactivity disorder). But the link was looser.

Two of the genetic variations affect changes in the brain's calcium channels. Calcium flow in these channels directly affects how brain cells develop and grow. But subtle differences in this process could lead to a major mental health condition.

What Changes Can I Make Now?

Companies already advertise genetic testing for certain psychiatric diseases. Before you consider taking such a test, be sure to understand the limitations.

It's not like testing for Huntington's disease. The genetic test for Huntington's disease will tell you if you have or have not inherited the gene. If you inherited the gene, you will develop the disease.

Right now, genetic testing for psychiatric conditions might indicate if you are at lower or higher risk. But that's all. Even if you are at higher risk, there is currently no lifestyle change you can make or medicine you can take to reliably lower your risk.

What Can I Expect Looking to the Future?

You can expect big changes in how mental health conditions are defined in the future. For example, it might turn out that a set of genetic variations defines a disease. But the disease might be able to have different symptoms. For example, perhaps bipolar disorder, major depression and schizophrenia are different expressions of the same disease.

These are very exciting times in psychiatry and all of medicine.