Heart rate could predict depression

Depression is a mood disorder that can have a debilitating effect on day to day life. It can cause physical symptoms, as well as feelings of sadness, anxiety, irritability, and lethargy and make it more difficult to concentrate, sleep, and talk. Depression may also increase the risk of certain health issues, such as heart disease.

If a person has been experiencing symptoms of depression every day for at least 2 weeks, they may be having a major depressive episode. In 2017, approximately 7.1% of the adult United States population had at least one of these episodes.

Depression can be treated with medication, talking therapies, or both. In either case, treatment can take months to be effective. Also, in some people, depression is resistant to treatment.

Recently, in the U.S., ketamine has been approved for use in these circumstances. Half of those with treatment-resistant depression may see a rapid improvement in symptoms after receiving ketamine administered by a clinician.

Ketamine’s effectiveness has opened the door to new research exploring ways of detecting depression. One such method involves studying heart rate.

Previous research has suggested a link between the variability of heart rate and depression. However, because the treatment of depression usually takes a long time, this link can be difficult to study.

As lead researcher of the present study, Carmen Schiweck, Ph.D., from Goethe University, in Frankfurt, Germany, notes, “We knew that something was going on to link heart rate to psychiatric disorders, but we didn’t know what it was and whether it would have any clinical relevance.”

“In the past, researchers had shown that depressed patients had consistently higher heart rates and lower heart rate variability, but because of the time it takes to treat depression, it had been difficult to follow up and relate any improvement to heart rate. But when we realized that ketamine leads to a rapid improvement in mood, we knew that we might be able to use it to understand the link between depression and heart rate.”

– Carmen Schiweck, Ph.D.

In the present pilot study, the researchers utilized ketamine’s rapid effectiveness to quickly assess the relationship between heart rate and depression.

To do so, they recruited 16 people with treatment-resistant major depressive disorder and 16 healthy people to act as a control group. The participants had their heart rates measured for 4 days and 3 nights.

Half of the participants with depression received ketamine, while the other half received a placebo.

The results were clear. As Schiweck explains: “We found that those with depression had both a higher baseline heart rate and a lower heart rate variation, as we expected. On average, we saw that depressed patients had a heart rate which was roughly 10 to 15 beats per minute higher than in controls.”

“After treatment,” she continues, “we again measured the heart rates and found that both the rate and the heart rate fluctuation of the previously depressed patients had changed to be closer to those found in the controls.”

Importantly, the researchers found that by feeding the heart rate data into an artificial intelligence program, the software was able to correctly identify the participants with depression and those without it.

“Put simply, our pilot study suggests that by just measuring your heart rate for 24 hours, we can tell with 90% accuracy if a person is currently depressed or not,” notes Schiweck.

The researchers also found that the heart rates of the participants with depression stayed elevated during the night, when it usually reduces. Moreover, participants with higher resting heart rates responded better to the ketamine treatment.

This could mean that diagnosis and treatment could be aided by analyzing the heart rate of anyone who presents with symptoms of depression.

Although the research is promising, Schiweck cautions that it is still in its early stages.

“We need to remember that this is a small proof-of-concept study. Six of our 16 initial patients responded to treatment with at least a 30% reduction on the [Hamilton Depression Rating Scale], so we need to repeat the work with a larger, antidepressant-free sample,” she says.

“Our next step is to follow up depressed patients and patients who are in remission to confirm that the changes we see can be used as an early warning system,” the researcher explains.