“Thus, it may be that HRV biofeedback somehow affects these brain structures, for example, increasing inhibitory control capacity or reducing hyperactivation in brain areas that are related to experiences of craving,” Muele added. “These presumed effects would also explain the positive effects of HRV biofeedback in a range of other mental disorders associated with affective dysregulation, such as depression and anxiety.”

Meule and his former colleagues at the University of Würzburg co-authored the first study investigating the impact of biofeedback on eating behavior.6 Their findings show that, compared with controls, participants with strong cravings who received 12 sessions of HRV biofeedback experienced decreased cravings, as well as a reduction in concerns related to eating and weight. Their sense of lacking control during cravings was also decreased by about 15%.

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In addition to the potential effect on relevant brain structures, it may be that the breathing techniques used in HRV biofeedback — or relaxation, in general — could be having an impact. Participants were instructed to breathe at a rate of six breaths per minute (one inhale and one exhale equal one breath), and to breathe deeply into their abdomen (rather than primarily into their chest, which equates to shallow breathing).

Shallow breathing can trigger the sympathetic nervous system, causing an increase in heart rate, blood pressure and stress hormones. A study conducted by researchers at Rutgers University and Yale University found a consistent association between shallow breathing and negative mood.7 In contrast, deep abdominal breathing activates the parasympathetic nervous system, and other researchers found that just one session of this kind of breathing activates the prefrontal cortex and increases the mood-regulating neurotransmitter serotonin.8

These effects may also help buffer postpartum stress in new mothers, according to findings reported in the December issue of Applied Psychophysiology and Biofeedback.2 One group of 25 participants used a portable HRV biofeedback device at home for one month after giving birth, while 30 control subjects did not. At the end of the study period, the biofeedback group showed a significant reduction in scores on the Edinburgh Postnatal Depression Scale, which was due primarily to decreased anxiety and improved sleep.