The REAL Cause of Bipolar Disorder
I have recently been diagnosed with bipolar disorder. What are the risks my children will inherit it?
The lifelong prevalence worldwide is anywhere from 0.3 to 1.6% for bipolar I disorder and larger for bipolar II disorder, with rates adding an additional 0.5 to 4% to the total number, depending on the epidemiological study.
Thus, regardless of one’s background, this is the risk for the development of the disorder. Now, supposing you have the diagnosis of bipolar disorder, how much greater is the risk to your child? We know that bipolar disorder, especially bipolar I disorder, has a major genetic component, with evidence coming from several studies.
First-degree relatives-that is, immediate family members who share 50% of your genes (siblings and children)-are around seven times more likely to develop bipolar I disorder than the general population. Additionally, the offspring of a parent suffering from bipolar disorder have a 50% chance of having another psychiatric disorder, independent of their chances of having bipolar disorder.
Identical twin studies demonstrate a concordance rate of 33% to 90%, depending on the study. That is, if you have bipolar disorder, the likelihood of your identical twin having the disorder is between 33% and 90%. For non identical twins, the concordance rate is between 15% and 20%. For first-degree relatives-hat is, brothers and sisters who are not twins or children of parents who suffer from the disorder-the concordance rate is between 5% and 10%.
Adoption studies demonstrate that the risks of developing bipolar disorder follow those of the biological parent and not the adoptive parent. Schizophrenic, schizoaffective, and manic syndromes appear to share genetic risk factors, suggesting that bipolar I disorder is more akin to a psychotic disorder than a mood disorder.
The fact that there is not 100% concordance between identical twins demonstrates, however, that environmental influences still have a role in the development of the disorder. Environmental effects can mean anything non-genetic, from local chemical environmental effects on the gene, to more global biological effects like fetal exposure to some as yet unidentified substance, to what are more commonly thought of as environmental factors such as family and social circumstances.
If a patient has negative family and social circumstances, environment is considered more of a trigger than an actual cause, and any genetic vulnerability may be either protected by a stable environment or, more typically, provoked or precipitated by an unstable environment.
Putting together genetic and environmental factors as contributors to the onset of bipolar disorder means that with a family history, an individual has a higher relative risk than anyone in the general population for developing bipolar disorder.
Stressful life events, specific environmental circumstances, or certain psychological processes may serve as a trigger of a manic episode in someone with a genetic predisposition for the disorder.
Term:
Relative risk – a ratio of incidence of a disorder in persons exposed to a risk factor to the incidence of a disorder in persons not exposed to the same risk factor.
