[Questioning the mechanism behind slow breathing and heart coherence training].

Background: Slow breathing and heart coherence training are being offered increasingly as treatments for anxiety, depression and stress-related mental and somatic complaints. Both of these interventions are aimed at influencing (i.e. increasing or optimising) heart rate variability and the mechanism involved is described in terms such as heart coherence, resonance breathing and heart-brain communication.
Aim: To find out whether treatment effects are indeed based on the optimisation of heart rate variability.
Method: Our literature search focused on 1) the assumption that poor mental health is definitely linked to deviant heart rate variability, and 2) the assumption that optimising heart rate variability leads specifically to a reduction of complaints and symptoms.
Results: There is insufficient evidence to support these two assumptions.
Conclusion: Slow breathing and heart coherence training probably achieve their effects as a result of non-specific psychological mechanisms.