A second genetic code that turns our genes on and off works differently in people who suffer from schizophrenia and bipolar disorder, Canadian researchers have discovered.

The finding helps explain a mystery that has puzzled psychiatrists for 50 years. Why, when one identical twin has schizophrenia, does the other have only a 40- to 60-per-cent chance of developing the severe mental illness?

One theory – from the emerging field of epigenetics – is that while their genes are virtually identical, the switches that control them are different. The result is too little or too much of the proteins that make up the brain and keep it running.

Read more in The Globe and Mail.