Thesis (Ph.D.) - University of St Andrews, October 2008.

Thought suppression is the attempted removal of unwanted thoughts. A plethora of previous research suggests that thought suppression is ineffective and possibly even counterproductive. However, the psychological processes involved in suppression are still underspecified. The current thesis aimed to examine the processes involved in thought suppression and to provide alternative techniques that may be more effective in the management of unwanted thoughts. To that end, Chapters 2 and 3 of the current thesis investigated the two key phenomena in the thought suppression literature, the immediate enhancement and rebound effects. Results from Experiments 1-4 indicated that participants, for the most part, found it difficult to suppress their thoughts during a five minute suppression phase, and also tended to have the unwanted thought re-emerge in a five minute phase following suppression, providing evidence for both the immediate enhancement and rebound effects. Chapter 4 (Experiment 5) provided a model of the immediate enhancement and rebound effects in terms of derived stimulus relations. The findings suggested that thought suppression attempts are ineffective due to the large number of intended and unintended environmental reminders. Experiments 6(a) and 6(b) extended on Experiment 5 by demonstrating how those relations might affect overt behaviour. Finally, Chapter 5 aimed to compare thought suppression with alternative strategies for dealing with unwanted thoughts. Acceptance and Commitment Therapy (ACT) was designed to undermine the negative behavioural consequences of derived stimulus relations. Experiments 7, 8 and 9 compared thought suppression with two components of the ACT model (i.e., mindfulness and defusion). The findings indicated, across both self report and behavioural measures, that the ACT techniques provided useful alternatives to thought suppression. In conclusion, the current thesis provides a behavioural model of the counterproductive nature of thought suppression whilst providing favourable evidence of alternative methods in the management of unwanted thoughts.

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

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Intrusive cognitions are a natural occurrence within our stream of consciousness, however, when they become repetitive, negative, distressing, and difficult to control, they may warrant clinical concern. Thought suppression is a common control strategy used to manage intrusive thoughts even though research suggests it may actually exacerbate the problem. Conversely, acceptance-based interventions have gained recent attention as an alternative strategy for managing distressing internal experiences. Only preliminary research has focused on the psycho- and neurophysiological bases of intrusive cognitions, and their relationship to cognitive control strategies. Evidence suggests that the anterior cingulate cortex (ACC) may be a brain region critically involved in this process. The present investigation compared the subjective, behavioral, and physiological effects of a thought suppression and acceptance strategy in a sample of university students with high or low obsessive-compulsive (OC) characteristics who were exposed to an emotion-evoking film clip. Participants were instructed either to suppress or accept any intrusive cognitions during a rest period after the film clip, while monitoring for the number of intrusions. Next, psychophysiological signals and reaction times were measured while participants performed a variant of the Stroop task. The commission of errors during a forced choice task generates an error-related negativity (ERN), which is believed to index activity in the ACC. Results showed that self-reported intrusions during the rest interval were greater for the acceptance group and the high-OC group. Correlations suggested that participants who reported more effort at suppression also indicated more distress about their thoughts, whereas those who reported more acceptance indicated less distress. During Stroop task errors, the ERN was apparent as a maximal frontal negativity, and was larger for the suppression group than the acceptance group at a frontal scalp site (Fz), but not a central scalp site (Cz). Correlations between self-reported intrusions at rest and ERN amplitude indicated that participants who reported fewer intrusions demonstrated enhanced ERNs, a marker for increased ACC activity. These findings may be interpreted as supporting the hypothesis that thought suppression is associated with increased ACC activity and greater self-reported discomfort with the intrusions.

Thesis (Ph.D.)--University of Central Florida, 2008. / Adviser: Stacey Tantleff Dunn. Includes bibliographical references (p. 122-137).

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Findings from numerous laboratory studies on thought suppression suggest that engaging in deliberate thought suppression may lead to the ironic effects of becoming preoccupied by the very same thoughts one wishes to avoid. Based on the results of these laboratory studies, a sophisticated model of thought suppression (i.e., Ironic Process Theory) has been developed. It has been argued that Ironic Process Theory can inform our understanding of the processes involved in the development and maintenance of clinical disorders such as PTSD. Unfortunately, to date, several important issues that are relevant to the successful application of this model specifically to PTSD have not been explored in detail. One such issue has to do with whether different types of thought suppression strategies that use different types of distracters lead to different levels of preoccupation. The current investigation examined whether the use of minor worries as distracters would lead to greater levels of preoccupation than the use of positive thoughts (Study 1). Eighty-one female undergraduates were assigned to one of three experimental conditions (suppress-worry, suppress-positive, control). Those in the suppression groups were asked to distract themselves from target thoughts using minor worries vs. positive thoughts whereas the participants in the control condition were asked to think about anything they liked. This was followed by instructions to think about anything for all three groups. Results indicated that although the two suppression groups differed on later preoccupation with previously suppressed thoughts, they did not do so in a significant manner. Study 1 also examined the potential mediating role of mental load when mental load is measured. No support for the mediational role of mental load was found. Study 2 further investigated the mediational role of mental load, this time through experimental manipulation. Forty female undergraduates were assigned to one of four experimental conditions (suppress-worry/no load, suppress-worry/load, suppress-positive/no load, suppress-positive/load). The same instructions used in Study 1 were given with the addition of a 10-digit number-recall task for those in the load condition. No support for the mediational role of mental load was found. Results are discussed in relation to theory and practice. / Ph. D.

This program of research was designed to examine the role of thought suppression in the retrieval of autobiographical memories (ABMs). The principal theory proposed here is that thought suppression is an important mechanism in explaining certain ABM retrieval patterns relevant to trauma and self-harm. Study 1 examined the role of thought suppression as a correlate of ABM retrieval in a nonclinical student sample, and showed that higher levels of thought suppression were significantly correlated with the faster recall of negative episodic ABMs as well as the recall of fewer personal semantic memories. Study 2 used a suppression manipulation procedure designed to examine whether this was a causal relationship, and revealed that induced thought suppression directly led to a significant enhancement in the retrieval of negative episodic ABMs as well as significantly fewer overgeneral first responses to negative cues. Furthermore, the induced thought suppression also resulted in the recall of significantly fewer personal semantic memories. Together these results support the theory that thought suppression is an important factor in ABM recall. The enhanced recall of negative memories could be particularly important in individuals who are self-harming, suicidal and/or suffering from PTSD, as enhanced negative recall has previously been observed in these populations. In order to further examine how thought suppression affects ABM retrieval and whether the enhanced negative recall observed in Study 2 was a result of mood-congruent recall, Study 3 used a similar suppression manipulation paradigm to examine the effects of induced thought suppression on mood. The results suggested that the enhanced negative ABM recall was unlikely to have been a by-product of the suppression manipulation resulting in a more negative mood state. Finally, Study 4 examined the role of thought suppression and ABM recall in a clinical sample of self-harming adolescents (who also reported high levels of post-traumatic stress symptoms). The results showed that levels of thought suppression were significantly higher in the self-harmers than the control group, indicating that thought suppression is an important coping mechanism in self-harmers. Furthermore, in terms of the autobiographical memory retrieval, it was found that the self-harmers were significantly faster in their retrieval of negative episodic ABMs and recalled fewer personal semantic memories than the control group. Multiple regression analysis of the data revealed that thought suppression remained as the most important predictor of variability in negative episodic ABM retrieval and personal semantic memory retrieval, even when variability explained by symptoms of depression and PTSD was considered. This program of research extends current theories of ABM retrieval by identifying thought suppression as a cognitive mechanism that directly affects the retrieval of both episodic as well as personal semantic ABMs. The theoretical importance and clinical relevance of this program of research are discussed.

The present research assessed whether levels of depression, anxiety and worry, obsessive-compulsive distress, and psychopathy were differentially related to distinct thought suppression profiles. As a means to achieving this goal, the Profiles of Everyday Thought Suppression (PETS) scale was constructed to measure the frequencies with which various target thoughts are suppressed. The PETS scale demonstrated good internal consistency and test-retest reliability, and scores were positively correlated with the general tendency to experience intrusions, the general tendency to suppress thoughts, neuroticism, and health complaints. Although the proportions of time people suppress thoughts was positively associated with the frequencies with which the thoughts are experienced, the strength of the associations differed across thought contents, suggesting that not all frequently experienced thoughts are invariably subject to suppression attempts. The frequency with which thoughts are generally suppressed was positively associated with overall levels of subclinical psychopathology experienced during the past month. When comparing across the various thought categories, results from multiple analytic strategies converged to suggest that specific subclinical psychopathological states are associated with particular sets of thoughts that are frequently suppressed. / Psychology