TO READ: Genetics of Depression, Bipolar Disorder and Schizophrenia
I recently attended a fascinating series of seminars at Stanford University's Bipolar and Schizophrenia Education Day. One lecture, given by Professor Doug Levinson, M.D., of Stanford, discussed what current research tells us about the genetics of these illnesses.

None of these mental disorders are as simple to follow through the family tree as, for example, eye color or blood type. The reason is that many different genes, not just one, combine forces to determine a person's susceptibility to depression, bipolar or schizophrenia. We don't yet know which of our 30,000 genes are involved. However, as scientists do "linkage studies" to physically locate these genes on human DNA, they're getting warmer. They are finding "peaks," or hot spots, on certain chromosomes for each of these three illnesses, though the peaks are at different places for each disease.

At this stage, it's clear only that these mental illnesses are caused partially by our genes, and partially by some aspect(s) of our environment. Studies show that bipolar disorder is 80-90% due to genetics; schizophrenia is 70-85% genetic; and major depression is 40-50% genetic. Furthermore, researchers have found that in the case of depression, people who have an early onset of symptoms (before age 20) have about a 50% genetic contribution to their illness, while those who have a single, later episode have about a 36% genetic contribution.

As further work allows us to eventually pinpoint a young person's genetic risk for such mental illnesses, perhaps earlier interventions and treatments will be able to avert, delay or lessen symptoms in those at high risk.