Acute mental stress assessment via short term HRV analysis in healthy adults: A systematic review with meta-analysis.

•Mental stress significantly reduced variability and chaotic behaviour of HRV.•Stress causes sympathetic activation and parasympathetic withdrawal.•Pooled HRV power ratio changed significantly while did not in individual studies.•Studies investigating HRV non-linear measures and mental stress are required.•The method proposed to meta-analyze HRV features can be adopted for other studies investigating HRV.