Finding a signal amid the noise
But heart rate and HRV aren’t foolproof biomarkers. Some studies have found that antidepressant use lowers HRV and that HRV changes aren’t unique to depression. There’s the added complication that depression often overlaps with other mental disorders.
“I think we’ve been very disappointed about the success of using particular biomarkers for particular disorders, because the majority of mental disorders are very heterogeneous,” said Andrew Kemp, PhD, psychology professor at Swansea University, Swansea, Wales. “A particular biomarker will, at the end of the day, be just one particular aspect of the overall profile that clinicians will have on particular individuals.”
The clinical utility of a heart rate–depression connection may go both ways.
For instance, depression could serve as a warning sign for atrial fibrillation, according to research from Parveen K. Garg, MD, associate professor of clinical medicine at the University of Southern California, Los Angeles. In a study involving more than 6,000 people, Dr. Garg showed that higher scores on depression scales correlated with a higher risk for the occurrence of atrial fibrillation over a follow-up period of about 13 years.
Depression is associated with other heart conditions as well. “A lot of data seem to suggest that just the presence of depression can increase risk for a whole range of cardiovascular problems,” said Dr. Garg. Epidemiologic studies have found associations between depression and the development of coronary heart disease and a modest increased risk for stroke.
“Things going on in your brain also have effects on the rest of your body,” said Dr. Garg. “Just recognizing this link, that maybe mental illness has an effect on other illnesses or diseases that can affect other parts of your body – I think that’s something we can share now.”
A version of this article first appeared on Medscape.com.