Hand in Hand: Depression and Heart Disease

High levels of homocysteine—a byproduct of protein metabolism that is linked to heart disease, stroke and dementia—seem to also increase a person's risk for developing depression.

Padraig E. O'Suilleabhain, a scientist at the University of Texas Southwestern Medical Center in Dallas, found in a study of 97 people recently diagnosed with Parkinson's disease that elevated blood levels of the amino acid homocysteine were linked to depression and other cognitive deficits. The study was published in the Archives of Neurology.

The research is part of a growing body of data showing that diseases of the heart and circulatory system—including diabetes and high blood pressure—are also bad for the brain. Whether homocysteine's toxicity to arteries causes depression is still under research. Studies have shown high levels of the amino acid often indicate a deficiency of B vitamins and folate, nutrients crucial for the production of mood-related neurotransmitters.