“While this is an important finding that merits further research, I would caution clinical application and oversimplifying diagnosis. Overall, this data does not validate cause and effect; there are numerous other variables to consider in determining diagnosis; and medicines to treat these conditions also affect heart rate. Patients and clinicians should not assume that an EKG alone will lead to diagnosis” – Samoon Ahmad, MD

https://psychcentral.com/news/2017/11/22/bipolar-or-depression-heart-test-may-help-tell-the-difference/129100.html