For the first time doctors have shown that measuring changes in 24-hour heart rate can reliably indicate whether or not someone is depressed.
In practical terms, this may give clinicians an objective "early warning" of potential depression, as well as a rapid indication whether or not treatment is working, so opening the way to more rapid and responsive treatment.
Presenting results of this pilot study at the ECNP virtual congress, lead researcher, Dr Carmen Schiweck (Goethe University, Frankfurt) said: "Put simply, our pilot study suggests that by just measuring your heart rate for 24 hours, we can tell with 90 per cent accuracy if a person is currently depressed or not".
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.