Paradoxical effects of thought suppression: a meta-analysis of controlled studies.

Research has shown that attempts to suppress a thought can cause an increase in the frequency of the thought. These paradoxical effects of thought suppression play a key role in cognitive-behavioral models of several emotional disorders. Laboratory studies of this phenomenon, however, have yielded mixed results; and narrative summaries of the literature have not been able to draw firm conclusions about the effects of thought suppression. We used meta-analysis to quantitatively examine the magnitude of thought suppression effects across controlled studies. Moreover, we explored whether the variability in effect sizes could be explained by methodological differences within and between studies. Results indicated a small to moderate rebound effect of thought suppression that varied in magnitude depending on the nature of the target thought and the method by which thought frequency was measured. Participants with clinical diagnoses did not show larger rebound effects than nonclinical or analogue participants, however, only a few studies included clinical samples. Findings are discussed in terms of implications for the ironic process theory of thought suppression, and avenues for future research on this phenomenon.