Genetics and Bipolar Disorder

We know that people are born with a genetic or biological predisposition to bipolar disorder. It is estimated that 2.6% of the population in the United States, 18 and older, has this illness. If one parent has bipolar disorder, there is a 15% to 30% chance that their child will have it also. However, being genetically at risk doesn’t mean that you will necessarily get this illness. It can skip generations or come in a milder form.

The term biological vulnerability is used to designate factors that are inherent in our bodies and nervous systems and cause us to have bipolar disorder. Biological vulnerabilities come in two forms, genetics and/or a biochemical imbalance. By genetics, we mean a coded gene active in our cell chromosomes, which predisposes us to an illness. The term biochemical imbalance is used to signify an error in the chemical composition of a brain process that impacts our thinking and moods. This can be caused by physical abnormalities in a nerve circuit or a part of the brain. These parts are present even when we are not having symptoms. Stress is often the trigger for our systems to become overactive. When a stressor brings vulnerabilities to the forefront, bipolar disorder is most likely to occur.

We know that genetics can influence the onset of bipolar disorder. To date, no single gene of major effect has been found that can be linked to the onset of this illness. Though promising research is continuing, this remains one positive avenue of investigation

Another approach is to presuppose there are many genes involved, each with a small effect. These small effects when taken as a whole, contribute to the genetic vulnerability. This can imagined by the following illustration:

Picture a number of concentric circles overlapping. Each circle represents a gene. Some circles touch, while others do not. Each represents a factor that contributes to the overall diagnosis of bipolar disorder.

Research has shown that those with this illness have low levels of neurotransmitters (communication links between nerve cells.) when in the depressive mode and higher levels when in the manic phase. This tells us something is wrong in the production of neurotransmitters, but we don’t yet have the precision to point to the area of the brain where misfiring is occurring.

Despite promising research, there is no biological or genetic test for chemical imbalance at this time. Identifying brain circuits may help us recognize persons at risk for the disorder, even when individuals are symptom free. The lack of a test makes it easy to forget or be skeptical of impairment. Identifying brain circuits could help us develop more effective treatment as well as maximize confidence in the diagnosis.

Possibilities, which would have been the stuff of science fiction only a few years ago, are the present front line in our quest to understand the brain and mental illness. While a cure is not yet on the horizon, present work in this area is advancing rapidly.