cases, the first symptoms of this progressive neurological disease are psychiatric ones (Kolata, 1986). Patients may be depressed or irrational, forgetful or disoriented. Those who do not start out with psychiatric symptoms start with movement disorders-clumsiness and an unsteady gait. So the example of Huntington's disease at least raises the possibility that complex psychiatric syndromes are caused by single genes.
             It has been suspected for years now that there is a strong genetic component to bipolar disorder. For example, if one identical twin has bipolar disorder, the other has a nearly 80% chance of having it too. If one member of a pair of fraternal twins has the illness, the other member has about a 20% chance of having it. When adopted persons with bipolar disorder were studied, investigators found that more than 30% of their biological parents also had bipolar disorder, but only 2% of the adoptive parents did (Kolata, 1986).
             The majority of patients with bipolar disorder will experience significant
             symptoms before the age of 25 years ( Suppes, Dennehy, Gibbons, 2000). However, there are some patients who develop new onset of illness in much later decades. Onset of symptoms of bipolar illness after the age of 60 years is likely due to secondary medi
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