The aim of this study was to utilize a subset population initially reported in Knowles and Bull (2003) to investigate the impact of perceived stress on individual psychological and physiological well-being. Of the original 129 participants participating in the 2003 study, 64 also completed the modified version of the Standard Shift-work Index (SSI) and two other questionnaires: the Perceived Stress Scale (PSS) and the General Health Questionnaire (GHQ). It was hypothesized that an analysis of the responses to these scales would indicate that age, disengagement, and perceived stress would be adversely related to well-being. Furthermore, it was also hypothesized that perceived stress would be a more influential covariate of well-being when compared to the covariates of age and disengagement coping. Analysis of the data provided partial support for the hypotheses that age, disengagement coping, and perceived stress were adversely related to a variety of psychological and physiological symptoms. In addition, results also indicate that the covariate of perceived stress accounted for a majority of the significant findings. Overall these findings provide evidence that, while age and disengagement coping moderate well-being, levels of perceived stress may play a more influential role.
Use of the term "stress" has become common and popular in today's society and, although many people claim to know what stress is, a review of the academic literature indicates that its definition is as diverse as the perspectives from which it is studied (Twain, 1999). Based on a review of the scientific literature, Twain (1999) suggests that stress may be derived from three distinct factors, including: (1) any environmental stimuli/us or event/s, (2) an internal/ subjective response, or (3) the body's reaction to an internal or external demand. It is also important to note that a stressor can be either positive or negative, for example a good stressor may be childbirth, while a bad stressor may be dealing with a lack of sleep. However, it is suggested that any stress initiated by psychological and/or physiological factors causes a state of disharmony in an individual's homeostasis. This state of disharmony, it is argued, subsequently leads to either an increased susceptibility to illness or an exacerbation of current symptoms.
While there are many methods to assess stress, this study utilized the Perceived Stress Scale (PSS) (Cohen, Kamarck, & Mermelstein, 1983). The PSS consists of 14 five-point Likert scale responses that assess an individual's global perceived stress, defined as, "the degree to which situations in one's life is stressful" (Johnston, Wright, & Weinman, 1995, p. 23). This particular assessment tool was selected due to three main factors: (1) its diverse use in the stress-based literature, (2) its high internal consistency and validity (Johnson, Wright, & Weinman, 1995), and (3) its focus on assessing global stress rather than specific states of stress caused by particular stressors that may influence an individual's feeling of stress (e.g., job related, family related, dealing with shift-work).
Shiftwork itself can be seen as a stressor (both psychological and physiological) and consequently, contribute to both psychological and physiological problems. Due to this, shiftwork studies have tended not to assess stress directly, instead assuming that it is indirectly accounted for in the measures being taken. For example, in the shiftwork literature, one popular research tool is the Standard Shiftwork Index (SSI) designed by Barton, Spelten, Totterdell, Smith, Folkard, and Costa (1995).
As indicated previously (Knowles & Bull, 2003) the SSI assesses both psychological and physiological well-being as well as various moderating/mediating factors such as personality and coping strategies (Barton, et al., 1995; Barton, Folkard, Smith, Spelten, & Totterdell, 1992). However, although the SSI measures specific aspects of stress indirectly (i.e., emotional/physical workload, emotional stress and time pressures at work) and the possible consequences of stress (i.e., chronic fatigue, psychological distress), it fails to specifically assess levels of perceived stress, despite the vast range of evidence indicating that perceived levels of stress are directly related to individual well-being (Cohen & Williamson, 1991).
While there have been several studies published in the shift-work literature assessing the impact of stress on individual well-being, they have tended to be a relatively small focal point of research. In a large study of 344 blue-collar workers investigating the impact of work, stress and psychosomatic complaint, Frese and Semmer (1986) found that both psychological and environmental stress were correlated with psychosomatic complaints, irritation/strains, and reports of ill health within a two-year period. Based on these findings, the authors concluded that stress might add to the impact of shift-work on an individual's psychological and physiological …