Schizophrenia and manic depression may have similar genetic cause

Schizophrenia and manic depression, major psychotic illnesses affecting about 2% of the population, may have a similar genetic cause new research suggests.

Both are partly characterised by delusions, but manic depression, or bipolar disorder, involves cycles of extreme high and low episodes.

Scientists examined the preserved brains of 15 subjects who had schizophrenia and 15 who had manic depression. The genetic make-up of the tissue was compared with that of 15 brains taken from subjects who had neither illness.

Certain genes involved in producing the myelin sheaths which insulate nerve cells were lacking in the brains of both psychosis groups and previous research had suggested abnormalities in the expression of myelin genes may play a role in schizophrenia.

"The high degree of correlation between the expression changes in schizophrenia and bipolar disorder provide compelling evidence for common pathophysiological pathways that may govern the disease phenotypes (observable traits)," said researcher Sabine Bahn, from Cambridge University.

The findings were reported yesterday in the Lancet medical journal.

In an accompanying commentary, Kenneth Davis from the Mount Sinai School of Medicine in New York said the results were 'intriguing' since the two diseases had different symptoms and were treated with different drugs.