UPDATE 1-St. Jude gets depression study under way

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CHICAGO, June 26 (Reuters) - St. Jude Medical Inc (STJ.N) said on Thursday that the first two patients had received its pacemaker-like implant as part of a clinical study to determine whether deep-brain stimulation will help people with severe depression.

A 59-year-old woman and a 42-year-old man were implanted with the St. Jude Medical Libra Deep Brain Stimulation System, an investigational device, at Alexian Brothers Behavioral Health Hospital in Chicago, the company said.

The stopwatch-sized device is implanted in the chest, with leads that send electrical impulses to specific parts of the brain thought to be involved in depression.

St. Jude's study is researching a specific area in the brain called Brodmann Area 25 that is thought to play a role in depression. Brain imaging studies indicate that Brodmann Area 25 appears to be overactive in severely depressed people.

Medtronic Inc (MDT.N) is also investigating whether its device, commonly known as a "brain pacemaker," can help severely depressed patients.

The National Institute of Mental Health estimates that more than 21 million U.S. adults suffer from some kind of depressive disorder. Current therapies are effective for about 80 percent of this patient population, according to the National Advisory Mental Health Council, leaving about 4 million adults who do not respond to medication, psychotherapy or electroconvulsive therapy.

Shares of St. Jude, which also makes cardiac pacemakers and implantable cardioverter defibrillators, were down 83 cents, or 2 percent, at $40.42 at midday amid a weaker broad market. (Reporting by Debra Sherman; Editing by Maureen Bavdek)