Bipolar Disorder: In the Genes?

Wednesday, October 10, 2007
By Tina Benitez

Bipolar disorder runs in the family. However, scientists still cannot pinpoint it to one specific gene since there are many other factors that may lead to the manic-depressive illness.

The disorder is 75 to 80 percent hereditary, according to Dr. Candida Fink, a child and adolescent psychiatrist and author of Bipolar Disorder for Dummies and The Ups and Downs of Raising a Bipolar Child. Stress, family life, emotional and psychological stresses should also be taken into account.

“It runs a pretty broad range,” said Fink. “Different stresses are likely contributors. Vulnerability and emotional and psychological stress is partly related, but it isn’t always one, and this is important to know. One can develop bipolar with stress or other things combined. We don’t know if it’s something biological or a mixture of developmental, hormonal imbalances.”

Fink said that some hereditary factors are strong indicators of whether someone will develop bipolar disorder or not. Identical twins have a 70 percent higher chance of developing bipolar disorder. If one parent is bipolar, there is a 7 to 10 percent higher risk of getting bipolar disorder. If there are two parents, there is a 20 percent chance of developing bipolar in the offspring because of the multiple genes.

“It’s a huge issue when getting family history and sitting with someone,” said Fink. “Does bipolar run in the family? Particularly, sometimes the further back you go, the family was not diagnosing it, or no one talked about it. It was kind of like, did you have an aunt Sally that never left the house? The most relevant indicator is the immediate family, which is typical of most mental illnesses, but there’s not just one thing that is going to give us the answer.”

Individuals who are bipolar will present signs of depression first, said Fink, but experts must look for the red flags in the different types of depression when diagnosing it. Was it onset at a young age or not? Were there some brief or discreet episodes in their past?

Dr. Francis McMahon, chief of the Genetics Unit of the Mood Anxiety Disorders Program at the National Institute of Mental Health (NIMH) in Bethesda, Md., said that it has been known for a long time that bipolar disorder and manic depression are the most genetic of all illnesses. There have been three kinds of studies, including family studies that show that bipolar disorder definitely runs in families. The other studies were conducted on twins, identical and fraternal.

“If you have a close family member, you have a 10-fold chance of getting bipolar disorder,” said McMahon. “If you do the math, there is about an 80 percent difference of risk of bipolar, which leaves about a 20 percent chance for other factors, and we know even less about what those are.”

Who Gets It — and Why?

For parents, Fink wants to develop a handbook for parents with children who may be bipolar, because there are so many different mood disturbances throughout childhood. “In studies of kids, there may be depression, but you have to ask if they really do look like the classic bipolar disorder,” Fink said. “There’s also attention deficit disorder, or other illnesses brought on by huge trauma. They have to understand the neurobiology component.”

There’s even a division between men and women when it comes to acquiring bipolar, because more women suffer from depression. Bipolar dramatic episodes may show up in the early 30s with more manic episodes later in life in the 40s. “A lot of bipolar disorder is struggling with depression, mostly reported in childhood. Manic episodes show up later, and that’s when you’re hit over the head with bipolar,” said Fink.

Life experiences, use of abusive drugs can also play a role in developing bipolar disorder, but any one of these can cause anxiety or depression, which may exacerbate bipolar episodes, according to McMahon. “Assuming that you are already susceptible, since it is in the family, there may be more of a chance of getting bipolar.”

McMahon added that if people are bipolar, they have to be aware of several things to control episodes including, but not limited, to:

— Missing nights of sleep

— Trans-meridian travel, which causes stress on the body

— Whether they have stress in the family

“Stress in general is not a good thing,” he said. “But in and of itself some people with bipolar have to watch out for stresses that may come from jet lag as well as occupational stress.

Work stress can lead to manic or depressive episodes, often in the case of someone getting a promotion or getting more responsibilities at work, which can tip them over into being susceptible. Bipolar also tends to be something people get early on in life, and according to McMahon, 80 percent of people who are bipolar will see signs of the illness when they are 24, but it doesn’t mean they will be diagnosed.

Once a psychiatrist goes over the family history with them, there may have been some illness that occurred in adolescence. People can go months and years being undiagnosed and continue to get a number of episodes down the line. “Bipolar is episodic,” he said. “A lot of studies are about what triggers the episode, but there’s very little evidence of why people get it.”

Med Alerts

Some of the bigger challenges with new medications used for treating bipolar disorders, according to McMahon is that there are a lot of drugs that treat the episodes, or prevent the episodes, but there’s nothing available to cure the illness. He added that the big challenge for big treatments in the next decade lie in genetic studies.

One group of studies that has made strides in linking bipolar, major depression and other diseases to the genes is the Bipolar Disorder Phenome Database, a collaboration of institutional research from NIMH, Johns Hopkins University, the University of Colorado’s Health Sciences Center, and the University of Heidelberg in Germany. The database includes 20 years of studies on bipolar individuals and those with a related illness and their family history.

He said that there is one gene, which has been clearly identified as influencing bipolar and other diseases, as well as two other genes that need to be reviewed more deeply.

McMahon said that researchers are seeing more and more linkage between specific genes and diseases, specifically bipolar disorder and depression, but it’s still not clear what happens to this genetic makeup, whether it is brought on hereditarily or from outside factors.

“It sounds like a big achievement, and it has had contradictory results, but it still feels like a big step forward,” he said. “We have a long way forward. We have to figure out how and what they do that goes wrong. If we talk six months from now, we may clearly have found specific genes that link between bipolar and depression.”