This undated illustration shows the DNA double helix
© AFP/HO/File PARIS (AFP) - Among people with schizophrenia, deletions and duplications are more common in key locations of the genetic code compared to otherwise healthy counterparts, according to the papers, released by the London-based journal Nature.
The studies cast a net through the genomes of thousands of people with schizophrenia and a large number of "controls" for comparison.
Schizophrenia is a complex brain disorder, characterised by delusions and hallucinations, that strikes around one person in 100 at some point in their lives -- usually in late adolescence or early adulthood -- and with often devastating results.
Scientists have long suspected that genes play a far more important role in the disease than environmental factors.
By some estimates, genetic factors could account for 73 to 90 percent of cases, but no big culprit genes have emerged so far. This has led investigators to look at a range of smaller, subtler genetic changes, which quite likely are linked, and such tiny variations can be difficult to detect.
The new studies, conducted by three international teams of scientists, point to locations on Chromosomes 1, 15 and 16, where telltale DNA changes were about 15 percent more frequent among people with schizophrenia.
They also confirmed earlier work that pointed the finger at an area on Chromosome 22.
Researchers said they had unlocked some fundamental knowledge about schizophrenia, but urged caution.
"The findings are impressive and (represent) hugely important leaps towards understanding the origins of schizophrenia," said Michael O'Donovan, a professor at Cardiff University in Wales, which is part of the International Schizophrenia Consortium, gathering 11 research institutes.
"But since only a small amount of the genetic risk for schizophrenia has been accounted for, they are not ready to be applied for genetic testing."
A number of biotech companies are now offering DNA tests for psychiatric disorders, although many experts say the genetic causes of mental ill-health remain poorly understood and inaccurate results could spur panic, confusion or complacency.
©AFP