To examine how positive affect influences ability to benefit from heart rate variability (HRV) biofeedback treatment for individuals with severe brain injury. Secondary data analysis of a nonrandomized experimental study that assessed the efficacy of biofeedback treatment for executive dysfunction in 13 individuals with chronic severe brain injury. Bivariate correlations between the predictors (levels of HRV and positive affect) and the outcome (change in Category Test errors) showed large effect sizes for higher levels of HRV coherence (r = -.495, p = .085) but not for positive affect (r = .069, p = .824). Although positive affect had a negligible effect on Category Test improvements by itself, positive affect played a moderating role that complemented the effect of HRV coherence. HRV coherence had a stronger effect on Category Test performance among those participants who demonstrated higher positive affect. A regression model was fit that included main effects for HRV coherence and positive affect, as well as their interaction. The interaction term was significant in a 1-tailed test (b = -3.902, SE = 1.914, p = .072). Participants who had the most positive emotions made the most gains in the HRV biofeedback training and performed better posttreatment on a test designed to measure problem-solving ability. Results indicate that positive affect can improve cognition, specifically mental flexibility and abstract thinking. Addressing factors that shape negative affect such as irrational beliefs and self-doubt is an important target for therapeutic intervention even in those with severe, chronic deficits. (PsycINFO Database Record
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