Bradley M. Appelhans

Heart Rate Variability as an Index of Regulated Emotional Responding

The study of individual differences in emotional responding can provide considerable insight into interpersonal dynamics and the etiology of psychopathology. Heart rate variability (HRV) analysis is emerging as an objective measure of regulated emotional responding (generating emotional responses of appropriate timing and magnitude). This review provides a theoretical and empirical rationale for the use of HRV as an index of individual differences in regulated emotional responding. Two major theoretical frameworks that articulate the role of HRV in emotional responding are presented, and relevant empirical literature is reviewed. The case is made that HRV is an accessible research tool that can increase the understanding of emotion in social and psychopathological processes.

Neurobehavioral Inhibition of Reward-driven Feeding: Implications for Dieting and Obesity

Overview The development of effective weight loss interventions requires a thorough understanding of the motivational factors that drive and inhibit the overconsumption of food. Obesity was once believed to result purely from disruptions of homeostatic mechanisms controlling food intake. However, it is increasingly recognized that much of the excess caloric intake in obesity is driven by pleasure or the rewarding properties of readily available palatable food (1,2). It is important to note that the motivation underlying this reward-driven or “hedonic” feeding appears to have a different neurophysiological basis than homeostatic controls over energy balance, though the hedonic and homeostatic systems do interact (3). Recently, a surge of research has linked the appetitive motivation to consume palatable food to activation of the mesolimbic dopaminergic system, a neural pathway also implicated in drug addiction and addictive behaviors such as gambling (4). As a result of these findings, a view of obesity as a “disorder of appetitive motivation” has gained prominence among a growing number of obesity researchers. However, a model of hedonic feeding based purely on appetitive motivation has limitations, including an inability to explain instances of feeding behavior parsimoniously in both dieters and nondieters. The aim of this review is to summarize the strengths and weaknesses of the appetitive model, present the extant literature linking control of hedonic feeding to inhibitory processes localized in the prefrontal cortex (PFC), and delineate a theoretical model in which hedonic feeding is viewed as the product of an interaction between appetitive motivation and inhibitory control.

Inhibiting food reward: delay discounting, food reward sensitivity, and palatable food intake in overweight and obese women

Overeating is believed to result when the appetitive motivation to consume palatable food exceeds an individuals capacity for inhibitory control of eating. This hypothesis was supported in recent studies involving predominantly normal weight women, but has not been tested in obese populations. The current study tested the interaction between food reward sensitivity and inhibitory control in predicting palatable food intake among energy‐replete overweight and obese women (N = 62). Sensitivity to palatable food reward was measured with the Power of Food Scale. Inhibitory control was assessed with a computerized choice task that captures the tendency to discount large delayed rewards relative to smaller immediate rewards. Participants completed an eating in the absence of hunger protocol in which homeostatic energy needs were eliminated with a bland preload of plain oatmeal, followed by a bogus laboratory taste test of palatable and bland snacks. The interaction between food reward sensitivity and inhibitory control was a significant predictor of palatable food intake in regression analyses controlling for BMI and the amount of preload consumed. Probing this interaction indicated that higher food reward sensitivity predicted greater palatable food intake at low levels of inhibitory control, but was not associated with intake at high levels of inhibitory control. As expected, no associations were found in a similar regression analysis predicting intake of bland foods. Findings support a neurobehavioral model of eating behavior in which sensitivity to palatable food reward drives overeating only when accompanied by insufficient inhibitory control. Strengthening inhibitory control could enhance weight management programs.

Heart rate variability and pain: associations of two interrelated homeostatic processes.

Between-person variability in pain sensitivity remains poorly understood. Given a conceptualization of pain as a homeostatic emotion, we hypothesized inverse associations between measures of resting heart rate variability (HRV), an index of autonomic regulation of heart rate that has been linked to emotionality, and sensitivity to subsequently administered thermal pain. Resting electrocardiography was collected, and frequency-domain measures of HRV were derived through spectral analysis. Fifty-nine right-handed participants provided ratings of pain intensity and unpleasantness following exposure to 4 degrees C thermal pain stimulation, and indicated their thresholds for barely noticeable and moderate pain during three exposures to decreasing temperature. Greater low-frequency HRV was associated with lower ratings of 4 degrees C pain unpleasantness and higher thresholds for barely noticeable and moderate pain. High-frequency HRV was unrelated to measures of pain sensitivity. Findings suggest pain sensitivity is influenced by characteristics of a central homeostatic system also involved in emotion.

Association of Post‐Traumatic Stress Disorder and Obesity in a Nationally Representative Sample

Recent studies suggest a possible link between post‐traumatic stress disorder (PTSD) and obesity risk, which would have implications for the development of obesity‐related diseases in this population. The present study examined the association between PTSD and obesity and whether this association differed by sex in a representative sample of the US population. A secondary objective was to determine whether the association between PTSD and obesity was mediated by binge eating disorder (BED). Data were from the Collaborative Psychiatric Epidemiology Surveys (CPES), which comprises three nationally representative cross‐sectional surveys that were conducted between 2001 and 2003. Logistic regression analyses weighted to represent the general US adult population were performed. In the total sample of 20,013 participants, rates of obesity were 24.1% for persons without a lifetime history of PTSD and 32.6% among persons with PTSD in the past year. Adjusting for socio‐demographic characteristics, depression, substance and alcohol abuse/dependence, and psychotropic medication status, past year PTSD was associated with greater likelihood of obesity (odds ratio (OR) = 1.51; 95% confidence interval (CI) = 1.18, 1.95), with no differences by gender. BED did not statistically mediate the relationship between PTSD and obesity. The present study provides support for a link between PTSD and obesity. Findings further existing literature by indicating that the association is consistent across sexes and is not statistically mediated by BED.

A Call for an End to the Diet Debates

As the obesity epidemic persists, the time has come to end the pursuit of the “ideal” diet for weight loss and disease prevention. The dietary debate in the scientific community and reported in the media about the optimal macronutrient-focused weight loss diet sheds little light on the treatment of obesity and may mislead the public regarding proper weight management. Numerous randomized trials comparing diets differing in macronutrient compositions (eg, low-carbohydrate, lowfat, Mediterranean) have demonstrated differences in weight loss and metabolic risk factors that are small (ie, a mean difference of <1 kg) and inconsistent. In the past year alone, 4 meta-analyses of diet comparison studies have been published, each summarizing 13 to 24 trials.1-4 The only consistent finding among the trials is that adherence—the degree to which participants continued in the program or met program goals for diet and physical activity—was most strongly associated with weight loss and improvement in disease-related outcomes. The long history of trials showing very modest differences suggests that additional trials comparing diets varying in macronutrient content most likely will not produce findings that would significantly

Early parental loss and salivary cortisol in young adulthood: The moderating role of family environment

Early family life adversity has been linked with negative physical and psychological health consequences in adulthood, possibly due to alterations in neuroendocrine activity. Young adults from families characterized by parental loss (N = 45) and control participants (N = 43) completed self-report measures of prior abuse and family conflict, and performed a stressful speech task designed to elicit neuroendocrine responses. Higher reported abuse and conflict were associated with increased cortisol for the loss group, but were unrelated to cortisol in the control group. Results indicate alterations in neuroendocrine functioning associated with early parental loss, which are moderated by the quality of the family environment.

Depression severity, diet quality, and physical activity in women with obesity and depression.

Major depressive disorder (MDD) is prevalent in clinical weight-loss settings and predicts poor weight-loss outcomes. It is unknown whether the severity of depressive symptoms among those with MDD is associated with diet quality or physical activity levels. This knowledge is important for improving weight-loss treatment for these patients. It was hypothesized that more severe depression is associated with poorer diet quality and lower physical activity levels among individuals with obesity and MDD. Participants were 161 women with current MDD and obesity enrolled in the baseline phase of a weight-loss trial between 2007 and 2010. Depression severity was measured with the Beck Depression Inventory II. The Alternate Healthy Eating Index was applied to data from three 24-hour diet recalls to capture overall diet quality. Daily metabolic equivalents expended per day were calculated from three 24-hour physical activity recalls. Greater depression severity was associated with poorer overall diet quality (estimate=-0.26, standard error 0.11; P=0.02), but not with physical activity (estimate=0.07, standard error 0.05; P=0.18), in linear regression models controlling for income, education, depression-related appetite change, binge eating disorder, and other potential confounds. Associations with diet quality were primarily driven by greater intake of sugar (r=0.20; P<0.01), saturated fat (r=0.21; P<0.01), and sodium (r=0.22; P<0.01). More severe depression was associated with poorer overall diet quality, but not physical activity, among treatment-seeking women with MDD and obesity. Future studies should identify mechanisms linking depression to diet quality and determine whether diet quality improves with depression treatment.

Delay discounting and intake of ready-to-eat and away-from-home foods in overweight and obese women

A shift from home-prepared to away-from-home and ready-to-eat foods has occurred in recent decades, which has implications for obesity and health. This study tested whether delay discounting, a facet of impulsivity reflecting sensitivity to immediate reward, is associated with the frequency of consumption and typical amount consumed of home-prepared, away-from-home, and ready-to-eat foods among overweight and obese women. Seventy-eight participants completed a binary choice task assessing discounting of delayed monetary rewards. Nutrient analysis of weighed food records characterized dietary intake over seven consecutive days. Foods were categorized as home-prepared, away-from-home, or ready-to-eat by a registered dietitian from information provided by participants. Delay discounting was not associated with the frequency of consuming home-prepared, away-from-home, and ready-to-eat foods as reflected in the percentages of recorded foods or total energy intake from each category. However, once consuming away-from-home and ready-to-eat foods (but not home-prepared foods), impulsive women consumed more energy than less impulsive women. Exploratory analyses indicated that more impulsive women chose away-from-home foods with a higher energy density (kcal/g). Impulsivity was associated with the quantity of away-from-home and ready-to-eat foods consumed, but not the frequency of their consumption. Home food preparation may be critical to weight control for impulsive individuals.

Nicotine effects on affective response in depression-prone smokers

RationaleComorbidity between cigarette smoking and depression is thought to arise because depression-prone smokers self-administer nicotine to improve mood. Yet little evidence supports this view, and nicotine’s effect on positive affect deficiency in depression remains largely unstudied.ObjectivesWe hypothesized that (1) nicotine would dispel negative affect and enhance positive affect and (2) effects would be stronger for smokers vulnerable to depression, particularly during a depressed state.Materials and methodsRegular smokers (N = 165) were recruited from the community: 63 with no history of major depressive disorder (MDD), 61 with recurrent past but no current MDD, and 41 with both current and past MDD. During four sessions, participants smoked either a nicotinized (NIC+) or denicotinized (NIC−) cigarette double blind after experiencing a negative mood induction or while undergoing a positive mood induction. Positive and negative affects were measured at baseline and at two time points after smoking.ResultsPreviously depressed smokers showed a heightened positive mood response to positive mood induction when smoking a nicotinized cigarette. Nicotine also increased the degree to which positive mood induction dispelled negative mood in depression-vulnerable smokers. Finally, nicotine worsened the negative affect response to negative mood induction for all groups.ConclusionSelf-administering nicotine appears to improve depression-prone smokers’ emotional response to a pleasant stimulus.