* Two separate studies find same genetic link
* Scientists hope findings will lead to better treatments
* Depression a common and costly disorder worldwide
By Kate Kelland
LONDON, May 16 (Reuters) - Scientists say they have
discovered the first solid evidence that variations in some
peoples' genes may cause depression -- one of the world's most
common and costly mental illnesses.
And in a rare occurrence in genetic research, the findings
by a British-led international team have been replicated at the
same time by another group from Washington University who were
studying an entirely separate group of people.
The researchers said they hoped the findings would bring
scientists closer to developing more effective treatments for
patients with depression, since currently available medicines
for depression only work in around half of patients.
"These findings ... will help us track down specific genes
that are altered in people with this disease," said Gerome Breen
of King's College London's Institute of Psychiatry, who led one
of the studies.
He added, however, that any new drugs developed from these
findings would be unlikely to be ready for treating patients for
another 10 to 15 years.
The first study analysed more 800 families with recurrent
depression, while the second examined depression and heavy
smoking in a series of families from Australia and Finland.
Both studies were published in the American Journal of
Psychiatry on Monday and both teams reported a strong link
between depression and genetic variations in a region called
chromosome 3p25-26.
"What is remarkable is that two different data sets,
gathered for different purposes and studied in different ways
found exactly the same region," said Breen, who gave a briefing
in London about the work. "Normally in genetic studies of
depression, replication of findings is very difficult and
frequently takes years to emerge, if ever.
Major depression affects around 20 percent of people at some
point in their lives. Severe and recurring depression affects up
to 4 percent of people and is notoriously hard to treat.
The World Health Organisation has forecast that depression
will rival heart disease as the health disorder with the highest
disease burden in the world by 2020.
According to a 2006 study, depression is responsible for 100
million lost working days a year in England and Wales alone at a
cost of 9 billion pounds ($14.6 billion).
Studies of families with depression have indicated that the
disorder has a genetic link and scientists think around 40
percent of the risk of developing it is contributed by genes,
with the rest down to environmental and other external factors.
"We are just beginning to make our way through the maze of
influences on depression and this is an important step toward
understanding what may be happening at the genetic and molecular
levels," Michele Pergadia, who worked on Washington University
study, said in a statement about the findings.
Breen's team is now conducting detailed gene sequencing
studies in 40 of the families involved in the first study to try
to find specific genes and variations that show a link.
(Editing by Alison Williams)
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