Monday, July 22, 2013

Positive feedback loop between social connections, positive emotions, and vagal tone.

Kok et al. suggest that positive emotions, positive social connections, and physical health reinforce one another in a positive feedback loop.They use cardiac vagal tone as an objective proxy for physical health. Indexed at rest as variability in heart rate associated with respiratory patterns, vagal tone reflects the functioning of the vagus nerve, which is the 10th cranial nerve and a core component of the parasympathetic nervous system, which regulates heart rate in response to signals of safety and interest. Low vagal tone has been linked to high inflammation, greater risk for myocardial infarction, and lower odds of survival after heart failure.

Their positive feedback loop suggestion sounds good - and is consonant with many recent studies correlating positive emotions, physical health, and longevity - but they do tend to confuse cause and correlation, and do not have appropriate control groups. A 'waiting list control group' really doesn't hack it. A control group should at least have some sort of experimenter engagement with subjects that is as similar as possible to the control group except without the exercises for self-generated positive emotions. Still, the results do show convincing correlations between vagal tone, positive emotions, and social connections in a group that receives training and practices loving kindness meditation for 61 days. Here is the abstract:
The mechanisms underlying the association between positive emotions and physical health remain a mystery. We hypothesize that an upward-spiral dynamic continually reinforces the tie between positive emotions and physical health and that this spiral is mediated by people’s perceptions of their positive social connections. We tested this overarching hypothesis in a longitudinal field experiment in which participants were randomly assigned to an intervention group that self-generated positive emotions via loving-kindness meditation or to a waiting-list control group. Participants in the intervention group increased in positive emotions relative to those in the control group, an effect moderated by baseline vagal tone, a proxy index of physical health. Increased positive emotions, in turn, produced increases in vagal tone, an effect mediated by increased perceptions of social connections. This experimental evidence identifies one mechanism—perceptions of social connections—through which positive emotions build physical health, indexed as vagal tone. Results suggest that positive emotions, positive social connections, and physical health influence one another in a self-sustaining upward-spiral dynamic.

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