In a new study, researchers found that measuring changes in 24-hour heart rate can reliably indicate whether or not someone is depressed.
This may give clinicians an objective “early warning” of potential depression, as well as a rapid indication of whether or not treatment is working, so opening the way to more rapid and responsive treatment.
The research was conducted by a team at Goethe University, Frankfurt, and elsewhere.
Scientists have known that heart rate is linked to depression, but until now they have been unable to understand exactly how one is related to the other.
In part, this is because while heart rates can fluctuate quickly, depression both arrives and leaves over a longer period, with most treatments taking months to take effect.
This makes it difficult to see whether or not changes in one’s depressive state might be related to heart rate.
According to the team, two innovative elements in this study were the continuous registration of heart rate for several days and nights, and the use of the new antidepressant ketamine, which can lift depression more or less instantly.
This allowed them to see that the average resting heart rate may change quite suddenly to reflect the change in mood.
Ketamine has a history as both an anesthetic and a party drug (a drug of abuse).
However in December last year, it was licensed to treat major depression in Europe, after having been introduced in the USA a few months earlier.
Traditional antidepressants can take weeks to show an effect, in contrast, ketamine is rapid-acting, with results often being seen in minutes.
The team worked with a small sample of 16 patients with Major Depressive Disorder, none of who had responded to normal treatment, and 16 healthy controls.
They measured their heart rates for 4 days and 3 nights, and then the volunteers with depression were given either ketamine treatment or a placebo.
The team found that those with depression had both a higher baseline heart rate and a lower heart rate variation.
On average depressed patients had a heart rate which was roughly 10 to 15 beats per minute higher than in controls.
After treatment, both the rate and the heart rate fluctuation of the previously depressed patients had changed to be closer to those found in the controls.
The most striking finding was that the scientists were able to use a 24-hour heart rate as a ‘biomarker’ for depression. Heart rates were measured using a wearable mini-ECG.
The data was fed to an Artificial Intelligence program, which was able to classify nearly all controls and patients correctly as being depressed or healthy.
The team also found that patients with a higher resting heart rate responded better to the treatment with Ketamine, which may help identify which patients are likely to respond to which treatment.
The team hopes to repeat the work with a larger, anti-depressant free sample.
Their 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.
One author of the study is Dr. Carmen Schiweck.
The study was presented at the European College of Neuropsychopharmacology (ECNP) virtual congress.
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