Schizophrenia has been long thought to be a heterogeneous disease, with many different pathways all leading to an illness with similar symptoms among its affected ranks. It is believed to be caused by a combination of genetic and environmental triggers, as there is a 50% chance of getting it if your identical twin does and a 10-15% chance if your parent or sibling does. Various environmental triggers appear to increase the risk of getting it, such as in utero infections, being born in the winter, and growing up in a family where there is a lot of yelling and emotional expressiveness. About one percent of the population has schizophrenia.
A recent study in Science of whole genome DNA in hundreds of people with and without schizophrenia finds that rare DNA mutations may more of a role to play than previously thought. From Scientific American: "In this study, researchers combed the genomes of 150 schizophrenia sufferers and 268 healthy individuals for never-before-seen copy number variations (CNVs)—mutations that result in large swaths of DNA encompassing multiple genes either being deleted or duplicated. Some such mutations have been found to be benign, but others have been implicated in ailments such as autism and cancer. The team of scientists, from research facilities across the U.S., found novel gene alterations in 5 percent of the healthy volunteers and 15 percent of the schizophrenia patients; new CNVs showed up in 20 percent of those subjects who developed symptoms at or before the age of 18."
53 different mutations were found in these patients. As more of these studies look at whole genomes from families with a high number of affected individuals (like mine, with 7 or 8 people with schizophrenia spectrum diagnoses), we will learn more about what goes wrong in these illnesses and how to better treat them.