Association between loneliness and computation of relationship value appears modulated by autonomic nervous functions.

Objectives: Recently, loneliness and social isolation have become common social problems. Previous research has shown that loneliness affects the brain's structure and function as well as the function of the autonomic nervous system. Our previous study found that loneliness has a negative impact on the computation of relationship value in response to commitment signals from friends. This study investigated whether heart rate variability (HRV), which is thought to reflect autonomic nervous function, is related to loneliness in young Japanese adults and whether experimental improvement of autonomic nervous activities alters the relationship value computation process in response to friends' commitment signals.

Design, material and methods: In Experiment 1, Japanese undergraduate students were assessed for loneliness and a resting electrocardiogram to determine HRV. In Experiment 2, other undergraduate students, separated into control and treatment groups, participated in a psychological task assessing responses to commitment signals from friends. The treatment group was subjected to autonomic nervous modulation before and while performing the task.

Results: Experiment 1 (n = 210) indicated that loneliness was negatively correlated with the high-frequency percentage (HF%) and positively correlated with the low-frequency (LF) component/HF ratio. Experiment 2, a pilot intervention study (n = 38), indicated that experimental improvement of HRV improved the subjective rating of the perceived commitment-confirming effect related to loneliness, specifically under high-cost commitment signal conditions.

Conclusion: These findings suggest that changes in cognitive functions caused by loneliness may be modifiable; by improving autonomic nervous function, it is possible to improve cognitive functions that have changed due to loneliness. However, as a pilot intervention study (Experiment 2) with a small sample, these pilot findings require replication in larger, adequately powered trials..