Self-focused thinking predicts nighttime physiological de-arousal.

Excessive focus on the internal self has maladaptive consequences for mental and physical health. Although the emotional functions of self-focus have been well established, no study has examined physiological arousal during the daily experience of self-focused thinking. The present study investigates the association between self-focus and autonomic activity using the experience sampling method with ambulatory monitoring of heart rate variability (HRV). Forty-five students reported the content of their thoughts during their daily activities while their heart rate (HR) was being recorded. Multilevel modeling analyses showed that HRV was lower (and HR was higher) over the sampling day if participants engaged in more self-focus, while HRV increased (and HR decreased) from midday to nighttime if participants did not engage in self-focused thinking. These results suggest that self-focus at night is associated with increased physiological arousal, and leads to inhibition of de-arousal associated with normal sleep processes. Implications for insomnia are discussed.