Blunted cardiac stress reactors exhibit relatively high levels of behavioural impulsivity

Highlights

• Blunted cardiac stress responders exhibited greater motor impulsivity.

• Blunted cardiac stress responders exhibited lower inhibitory control.

• Greater impulsivity may be a link to maladaptive health and behavioural correlates.

Abstract

Blunted physiological reactions to acute psychological stress are associated with a range of adverse health and behavioural outcomes. This study examined whether extreme stress reactors differ in their behavioural impulsivity. Individuals showing blunted (N = 23) and exaggerated (N = 23) cardiovascular reactions to stress were selected by screening a healthy student population (N = 276). Behavioural impulsivity was measured via inhibitory control and motor impulsivity tasks. Blunted reactors exhibited greater impulsivity than exaggerated reactors on both stop-signal, F(1,41) = 4.99, p = 0.03, η_p² = 0.108, and circle drawing, F(1,43) = 4.00, p = 0.05, η _p ² = 0.085, tasks. Individuals showing blunted cardiovascular stress reactions are characterized by greater impulsivity which may contribute to their increased susceptibility to outcomes such as obesity and addiction.

Introduction

Individuals differ markedly in their biological reactions to standard psychological stress exposures [10]. In addition to long-standing and comprehensive evidence to show that those who exhibit exaggerated cardiovascular reactions to acute psychological stress are at increased risk of developing various manifestations of cardiovascular disease [11], there is accumulating support to suggest that attenuated cardiovascular stress reactions are associated with a range of adverse health and behavioural outcomes [54]. These adverse outcomes include obesity [14], [56], [62] and substance abuse addictions, such as tobacco [26], [32], [34], [59], [61], [64], alcohol [7], [21], [25], [47], [50], [63] and/or other non-prescription drugs [47], [50], [67]. Attenuated biological reactions to stress also appear to be a feature of those who meet the criteria for exercise dependence [37], gambling addiction [51], and disordered eating [33], [40].

A conceptual model has been proposed whereby modified frontolimbic function of the brain leads to reduced physiological stress reactivity, altered cognition, and unstable affect regulation which then leads to impulsive behaviours, with consequences for adverse health behaviours and addiction risk [46]. The association between impulsivity and cardiovascular stress reactivity in non-clinical populations is somewhat unclear. Two studies reported a negative association, higher impulsivity was related to lower cardiac reactivity [1], [49]. Of these studies, one study used a self-reported impulsivity measure [1], while the other examined the relationship in young children and measured pre-ejection period (PEP), a less commonly reported cardiovascular index, as opposed to the more common measure of heart rate, making comparability difficult (HR; [49]). One study reported a positive association between cardiovascular reactivity and an aspect of impulsivity, temporal discounting [24]. Finally, no clear association was observed by others [48], however, selection of groups was made from extreme impulsivity questionnaire scores rather than cardiovascular reactivity. In one of the few studies to have included behavioural as well as self-report measures of impulsivity, pre-adolescent children high in impulsivity had diminished cardiac responses to a mental arithmetic task [6]. To our knowledge, no study in a young adult population has examined the relationship between cardiovascular stress reactivity and impulsivity using behavioural measures of impulsivity.

Given that impulsivity is associated with the unhealthy outcomes linked to attenuated biological stress reactivity, we re-examined its relationship with cardiovascular stress reactivity. However, instead of the predominantly used self-report measures, we administered two behavioural tests of impulsivity to our participants, selected as unambiguously exaggerated or blunted cardiac reactors following the stress testing of a substantial young adult sample. We considered that pre-selecting on the basis of stress reactivity and using behavioural measures would afford a more powerful test of the hypothesis that blunted stress reactors would be characterized by greater impulsivity. The examination of a young adult sample is particularly important given that impulsivity during this stage provides exaggerated risks to health development and may signify deficits in brain maturation [58].