Can manic depression be genetically inherited?
There is definitely a genetic component, with some families showing much higher occurrences of bipolar disorder. An individual with a close relative such as a parent or sibling who is manic depressive is far more likely to also develop symptoms. However, this is not inevitable and not all family members will develop bipolar disorder, even in families where the overall incidence is very high. Strong evidence that genetics does not fully explain what causes bipolar comes from studies of identical twins. Remember, identical twins have the same genes. Yet in only 57% of cases of bipolar in an identical twin, does the other twin also turn out to have the disorder. If genetics were destiny, and if manic depressive illness was a purely genetic disease, then in 100% of cases, both identical twins would develop bipolar disorder. Family history is very important though, and should always be examined when trying to make a diagnosis. There is a 2% chance that an individual may have bipolar disorde
