The ability to suppress emotions and thoughts varies considerably from one individual to another (Werman, 1983). He defines suppression as the “volitional elimination or diminution from consciousness, by any means, of undesirable thoughts, feelings, or bodily sensations” (p. 413). The study of thought suppression has grown into a significant area of scientific inquiry. What has compelled the interest of the scientific community is the realisation that “suppression is not simply an ineffective tactic of mental control; it is counterproductive, helping assure the very mental state one had hoped to avoid” (Wenzlaff & Wegner, 2000, p. 59).
Individuals often suppress emotional thoughts that arouse negative emotions as a way of regulating mood and reducing distress (Petrie, et al., 1998). According to Booth and Petrie, the suppression of emotions requires ongoing psychological effort to accommodate the disparity between what one is feeling and what one is experiencing. This effort indicates an increase in sympathetic nervous system activity which may have unhealthy consequences if becomes habitual. The constant suppression of emotions affects the neuroimmune network resulting in immunosuppression, leading to adverse health outcomes, says Booth (2005).
Wegner’s (1992) study on “Instructed thought suppression” found paradoxically that typically the instruction to suppress a thought induces a remarkable preoccupation with that thought, and that the resultant sensitivity to these thoughts heightens emotionality. Furthermore, Wegner recorded that during the suppression of emotional thoughts, intrusive recurrences are associated over time with electrodermal responses. The conclusion is that emotional thoughts that are suppressed cause stronger psychophysiological responses than those that are not suppressed. Subsequent research measuring the tendency to suppress unwanted thoughts (Wegner & Zanakos, 1994) augments prior findings that suppression may be a precursor of psychopathological reactions ranging from obsession to depression to anxiety. Wegner and Zanakos conclude that the tendency to dislike negative thoughts and to react to them with suppression is associated with depression severity, and they suggest that thought suppression is therefore a useful way of understanding how people may become depression-prone.
The emergence in recent decades of the discipline of psychoneuroimmunology has advanced knowledge of the relationship between psychosocial factors, the central nervous system, the immune system, and disease (Keller, Schleifer, Barlett, Shiflett, & Rameshwar, 2000). It is now known that psychological experiences such as stress and anxiety can influence immune function, which in turn may have an effect on disease development and progression (Azar, 1999).
The idea that emotions and physiology mutually influence one another suggests that the immune system as part of our physiology may be affected by the expression of emotion (Booth, 2005). The expression and non-expression of emotion has been studied in chronic illness and in the quality of life of people living with or recovering from illnesses (Lepore & Smyth, 2002). Research findings provide strong evidence that the health benefits of emotional disclosure may result partially from effects on immune function (Booth & Petrie, 2002). As our emotions change, “the structure of our bodies changes and we experience our lives differently” (Booth & Petrie, 2002, p. 159). In other words, physiological changes accompany expression and suppression of emotions.