Science / Medicine : Clues to Depression

Depression that afflicts hundreds of thousands of Alzheimer’s patients may be caused by deterioration in parts of the brain that produce chemicals believed to keep people upbeat, researchers said last week.

About 30% of Alzheimer’s patients show depressive symptoms. To explore what might be causing their depression, Pennsylvania researchers autopsied the brains of 37 demented patients, mostly Alzheimer’s victims, including 14 who were also diagnosed with major depression. For comparison, the researchers studied brain tissue from seven non-demented elderly patients.

The depressed subjects showed significantly more evidence of deterioration in two areas of the brain stem--the locus ceruleus and the substantia nigra--than the non-depressed subjects, the researchers found.

These parts of the brain produce two neurotransmitters believed to be important in keeping people free of depression--norepinephrine, which is involved in mood and sleep cycles, and dopamine, which is involved in physical movement.