Rumination and Cognitive Distraction in Major Depressive Disorder: An Examination of Respiratory Sinus Arrhythmia

Difficulty regulating emotions following stressful events is a hallmark of Major Depressive Disorder (MDD). Although individuals' ability to regulate their emotions is believed to have direct consequences for both emotional and physical wellbeing, few studies have examined the cardiovascular effects of different emotion regulation strategies in MDD. To the best of our knowledge, the current study is the first to examine the effects of two emotion regulation strategies, cognitive distraction and rumination, on both self-reported sadness and respiratory sinus arrhythmia (RSA) in individuals with MDD and healthy controls (CTLs). Following a forced-failure stressor, participants were randomly assigned to a rumination or cognitive distraction condition. As expected, rumination increased sadness and triggered RSA withdrawal for both MDDs and CTLs. Interestingly, although cognitive distraction reduced sadness, it also triggered RSA withdrawal. Moreover, cognitive distraction was associated with greater RSA withdrawal for MDDs than CTLs. Thus, although depressed individuals are able to use cognitive distraction to emotionally recover from stress, it may be associated with greater cognitive effort. Adding low-cost physiological measures such as RSA into assessments has the potential to offer new and important information about the effects of emotion regulation on mental and physiological health.

Aerobic exercise and strength training effects on cardiovascular sympathetic function in healthy adults: a randomized controlled trial

OBJECTIVE

Exercise has widely documented cardioprotective effects, but the mechanisms underlying these effects are not entirely known. Previously, we demonstrated that aerobic but not strength training lowered resting heart rate and increased cardiac vagal regulation, changes that were reversed by sedentary deconditioning. Here, we focus on the sympathetic nervous system and test whether aerobic training lowers levels of cardiovascular sympathetic activity in rest and that deconditioning would reverse this effect.

METHODS

We conducted a randomized controlled trial contrasting the effects of aerobic (A) versus strength (S) training on indices of cardiac (preejection period, or PEP) and vascular (low-frequency blood pressure variability, or LF BPV) sympathetic regulation in 149 young, healthy, and sedentary adults. Participants were studied before and after conditioning, as well as after 4 weeks of sedentary deconditioning.

RESULTS

As previously reported, aerobic capacity increased in response to conditioning and decreased after deconditioning in the aerobic, but not the strength, training group. Contrary to prediction, there was no differential effect of training on either PEP (A: mean [SD] -0.83 [7.8] milliseconds versus S: 1.47 [6.69] milliseconds) or LF BPV (A: mean [SD] -0.09 [0.93] ln mm Hg(2) versus S: 0.06 [0.79] ln mm Hg(2)) (both p values > .05).

CONCLUSIONS

These findings, from a large randomized controlled trial using an intent-to-treat design, show that moderate aerobic exercise training has no effect on resting state cardiovascular indices of PEP and LF BPV. These results indicate that in healthy, young adults, the cardioprotective effects of exercise training are unlikely to be mediated by changes in resting sympathetic activity.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT00358137.

The effects of exercise withdrawal on mood and inflammatory cytokine responses in humans

Mechanisms underlying the relationship between exercise and mood are not well understood. This study sought to investigate the role of pro- and anti-inflammatory cytokines and autonomic balance in determining the impact of exercise withdrawal on negative mood. Healthy men and women who regularly exercised (N = 26, mean age = 25.5 years, SD = 4.5 years) were randomised to exercise withdrawal or exercise maintenance for 2 weeks. Protocol adherence was monitored using accelerometers. Inflammatory markers from plasma (interleukin-6, IL-6; tumour necrosis factor-alpha; interleukin-10; and interleukin-1 receptor antagonist), heart-rate variability (HRV) and measures of mood (General Health Questionnaire-28 (GHQ) and the Profile of Mood States (POMS)) were assessed at study entry and at 2-week follow-up. Exercise withdrawal resulted in significant increases in negative mood over time on both the GHQ (p = 0.028) and the POMS (p = 0.005). Following the intervention, IL-6 concentration was lower in the exercise withdrawal than exercise maintenance condition (p = 0.05). No intervention effects were observed for other cytokines or HRV. The mood changes were significantly related to changes in IL-6 concentration (β = - 0.50, p = 0.011), indicating that reduction in IL-6 was related to increased negative mood. Our results are consistent with positive effects of exercise on mental health, but further research on inflammatory pathways is warranted.