There is considerable evidence documenting associations between tobacco smoking, including initiation, maintenance, and relapse of addiction, with diminished cardiovascular responses to acute psychological stress. However, less is known about how smokers respond to repeated stress across time. The current study examined patterns of cardiovascular reactivity and adaptation to recurrent stress among abstinent smokers, smokers who continued to smoke at their normal rate, and non-smokers. Smokers were randomly assigned to one of two conditions; ad libitum (n = 42), or 24h abstinence (n = 61); and non-smokers (n = 43) provided comparative referencing. Across the two laboratory sessions, participants (n = 149) were asked to complete a modified version of the trier social stress test (TSST), while monitoring systolic and diastolic blood pressure, and heart rate activity. Results showed that while non-smokers had elevated cardiovascular reactivity to begin with, they showed a greater capacity to habituate to recurrent stress across sessions. The data also suggest that smokers displayed attenuated cardiovascular reactivity to acute psychological stress and showed little habituation to repeated stress. In adjusted models, smokers exhibited less systolic blood pressure tolerance to stress. This poorer response profile in smokers may be a potential mechanism that leads to further cardiotoxic effects on health. Key words: Smoking, cardiovascular reactivity, habituation, stress

Diminished cardiovascular reactivity is a proposed marker of motivational dysregulation and is related to a range of adverse behavioural and health outcomes. Social participation represents the frequency an individual engages in social activities, is a form of motivated behaviour, and has been recently linked to lower cardiovascular responses to acute psychological stress. With recent work emphasizing the importance of assessing adaptation of the cardiovascular response to recurrent stress, the aim of the current study is to build on previous work by examining the relationship between social participation and cardiovascular stress response adaptation. Analyses were conducted using a general linear model and previously obtained data from the Pittsburgh Cold Study 3 (PCS 3). Two hundred and thirteen participants (M = 30.13; SD = 10.85) completed a social participation measure and had their systolic and diastolic blood pressure (SBP, DBP) and heart rate (HR) monitored across two separate standardized stress testing sessions. In line with previous research, lower social participation was related to lower cardiovascular responses to stress. Findings also indicate that higher levels of social participation were associated with greater blood pressure habituation to recurrent stress. Given that cardiovascular habituation to recurrent stress signifies good health, the implications of these findings are discussed. Key words: social participation, cardiovascular reactivity, cardiovascular habituation, blood pressure, Pittsburgh Cold Study.