Abstract
BACKGROUND: Disorders associated with mental health significantly impact disability-adjusted life year values and represent an ongoing problem in stressed societies. Worsening mental health also affects cognitive function and quality of life. Increasing attention has thus been attracted to preventive measures for mental and brain health in daily life. This has created a growing interest in care using laughter. This study assessed the effects of a short-term, laughter-based intervention on the mental health and cognitive functions of middle-aged adults. METHODS: The study applied a single-blind, crossover-controlled trial design. Cognitive tasks (e.g., digit vigilance) were performed after participants viewed a video clip of approximately four minutes (comedic or control video), and the resulting scores were treated as the primary endpoint. The secondary endpoints included cerebral blood flow in the dorsolateral prefrontal cortex (measured using NIRS), heart rate variability (calculated from ECG), subjective mood assessment, and salivary stress biomarkers (e.g., α-amylase activity). RESULTS: The study was conducted on 25 healthy Japanese-speaking adults aged 40 to 65. Results revealed a significant increase in digit vigilance scores. Compared to viewing the control video, participants evinced a trend toward an increase in serial seven subtraction scores after viewing the comedic video. No significant differences were found for other cognitive tasks. The cerebral blood flow was also significantly higher in the dorsolateral prefrontal cortex during the cognitive tasks performed after the participants viewed the comedic video compared to the control video. The outcomes of heart rate variability, subjective mood state assessment, and salivary stress markers also suggested that the comedic video intervention could subsequently contribute to the activation of parasympathetic activity and reduce psychological stress levels. CONCLUSIONS: The outcomes indicated that interventions using short comedic videos can improve focus and may reduce psychological stress. These results support the clinical benefits of humor, which can be utilized as a simple, non-invasive approach to promoting the health of middle-aged adults. TRIAL REGISTRATION: The study was approved by the ethics committee of Kirin Holdings Company (No. 2020-014) and registered in the University Hospital Medical Information Network (UMIN) database (Registration No. UMIN000043332; http://www.umin.ac.jp/ctr/ ) on February 15, 2021.