“…Nevertheless, this assumption has been questioned based on findings that community participants only experience a limited number of intrusions with content similar to that of clinical obsessions (Rassin, Cougle, & Muris, 2007;. However, the vast majority of studies, beginning with the pioneering work by Rachman and de Silva (1978), indicate the opposite: that is, that unwanted intrusive cognitions with the same contents as clinical obsessions are experienced by 80-90% of non-clinical participants (e.g., Belloch, Morillo, Lucero, Cabedo, & Carrió, 2004;Edwards & Dickerson, 1987;Freeston, Ladouceur, Thibodeau, & Gagnon, 1991;Niler & Beck, 1989;Parkinson & Rachman, 1981;Purdon & Clark, 1993, 1994a, 1994b. Since cognitive-behavioral therapy (CBT) models of obsessions propose that clinical obsessions have their origins in normal obsession-like intrusive thoughts, evidence of qualitative differences between non-clinical and clinical intrusive thoughts would constitute a serious challenge to the internal validity of CBT models.…”