Impact of psychological inflexibility on depressive symptoms and sleep difficulty in a Japanese sample

Background: Psychological inflexibility is a core concept in the acceptance and commitment therapy (ACT) model. The current study hypothesized and tested two models in which psychological inflexibility was linked with higher levels of depressive symptoms and sleep difficulty. Results: To attain data, Japanese university students (N = 633) completed questionnaires related to psychological inflexibility, depressive symptoms, and sleep difficulty. Psychological inflexibility was significantly correlated with higher levels of both depressive symptoms (r = 0.61) and sleep difficulty (r = 0.39). Structural equation modeling showed that psychological inflexibility was associated with higher levels of depressive symptoms after controlling for the effect of sleep difficulty. Additionally, psychological inflexibility was correlated with higher levels of sleep difficulty after controlling for the effect of depressive symptoms. These findings might assist with motivating clinicians to use ACT for insomnia. Conclusions: The current study found that greater psychological inflexibility was linked with high levels of depressive symptoms and sleep difficulties. These findings might assist with motivating clinicians to use ACT for insomnia.