somebody looking at the patient's environment could say, "well, the environment's also the same "in thmily, and maybe that transmits the illness." we have reasons to believe from twin studies, where identical twins have the same genetic material, that the likelihood of transmission is much grter. and there's been efforts to identify the genes which have come up with findings which have not yet held up. so we don't have genetic proof, ultimate proof, but the evidence is very strong for genetic transmission in both bipolar and unipolar illness, but it's strongest in bipolar. so rodney probably inherited a predisposition for bipolar disorder from his mother, mostikely a dysfunction in how the brain works. in this highly schematic drawing, nerve cells in the brain carry information in the form of electrical impulses along the length of the cell. for the impulse to cross the synapse-- the space between the cells-- a chemical called a neurotransmitter must be released into the synapse. the neurotransmitters move across the space and lock into specific receptor sites on the next cell. that's norm