Hearing laughter improves the recovery process of the autonomic nervous system after a stress-loading task: a randomized controlled trial

BackgroundIt has become necessary to develop mental health management methods that do not require specialized skills or tools to implement. With this in mind, we performed a subjective and objective investigation of the stress-reducing effect of hearing laughter.MethodsNinety healthy students were randomly assigned to a laughter (n=45) or rest (n=45) group. Both groups were then administered the Uchida-Kraepelin test for 15min, which served as a stress-loading method. The laughter group listened to a specially prepared CD for five minutes, while the rest group rested for five minutes. The participants' subjective stress level was assessed using a visual analogue scale and their physiological status was assessed by measuring blood pressure and monitoring heart rate variability.ResultsThe visual analogue scale score for subjective stress was found to decrease significantly in both the laughter and rest groups after the intervention. However, a two-way repeated-measures analysis of variance revealed significant interaction and main effects for the change in heart rate and the natural logarithm of the high-frequency component of heart rate variability (lnHF). A post-hoc analysis using Dunnett's test showed that hearing laughter caused the lnHF to significantly increase compared to that recorded during the Uchida-Kraepelin test and the rest period.ConclusionsThese results suggest that hearing laughter might produce a relaxing effect by increasing parasympathetic nervous activity. This would make it an easily accessible method for improving the recovery process of the autonomic nervous system after a stress-loading task that does not require specialized skills or tools.