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Brazilian Journal of Psychiatry

Print version ISSN 1516-4446On-line version ISSN 1809-452X

Rev. Bras. Psiquiatr. vol.37 no.4 São Paulo Oct./Dec. 2015 


Is “plausibility” a core feature of obsessions?

Pedro Morgado1 

1Life and Health Sciences Research Institute (ICVS), School of Health Sciences, Universidade do Minho, Braga, Portugal. Laboratório Associado ICVS/3B’s, Braga/Guimarães, Portugal. Hospital de Braga, Braga, Portugal. Clinical Academic Center-Braga (2CA), Braga, Portugal

Obsessions are unwanted, intrusive, recurrent, and persistent ideas, thoughts, images, or impulses that cause intense anxiety and are recognized as self-generated. The word obsession derives from the Latin word obsidere, which means being occupied, preoccupied, or taken into possession. In his General psychopathology, Karl Jaspers identified essential characteristics of obsessional symptoms, including a nonsensical and absurd quality, compelling force of thoughts, the belief that thoughts can influence events, need for order, and unacceptable impulses.1

Later, ego-dystonia and insight were identified as core features of obsessions, crucial for differential diagnosis between obsessive-compulsive disorder (OCD), obsessive-compulsive personality disorder (OCPD), and psychotic disorders.2 Ego-dystonia reflects the conflict (or disharmony) between an idea, a thought, an impulse, an image, or an act and the subject and/or the subject’s self-image. Insight is the extent of knowledge that one has about one’s own thoughts and acts.

During 2014, we followed 76 patients with OCD, four of whom had a comorbid psychotic disorder, in our obsessive-compulsive spectrum disorders clinic at Hospital de Braga (Braga, Portugal). We analyzed patient files, collected information on OCD severity, and categorized obsessions and compulsions by their “plausibility” or “bizarreness.” Apart any absurd quality, an obsession was considered plausible if there was a chance (even if remote) of it actually occurring; e.g., the obsession that someone will die if the patient does not say a specific word is absurd, but the feared consequence (the death of another) is possible, plausible, and understandable. An obsession was considered bizarre if it was implausible, not understandable, and not derived from ordinary life experiences; e.g., the obsession that one could be trapped inside a bottle if it were closed while one’s eyes were open is a bizarre thought that cannot happen.

Our analysis did not reveal statistically significant differences in age, gender, or OCD severity, as assessed by Yale-Brown Obsessive-Compulsive Scale (Y-BOCS), between patients with OCD without and with comorbid psychosis (Table 1). Interestingly, we found that the only patients with implausible and/or bizarre obsessions were those with comorbid psychosis. This observation pointed out “plausibility” as a putative core feature of typical OCD obsessions. Despite anecdotal case reports of bizarre obsessions in the context of OCD,3 increasing evidence on the high prevalence of obsessive-compulsive symptoms (OCS) and comorbid OCD in patients with schizophrenic disorders4 points to the possibility of an undiagnosed comorbid psychosis in those patients.

Table 1 Comparison between patients with obsessive-compulsive disorder with and without comorbid psychosis 

Characteristic OCD with comorbid psychosis (n=4) OCD without comorbid psychosis (n=72) Statistics
Age (years) 26.75±3.50 (23-31) 30.78±10.70 (18-62) U = 0.695
Female/male (n) 2/2 41/31 χ2(2, n=76) = 0.074, p = 0.785
Y-BOCS (total score) 26.75±5.25 (19-30) 25.40±5.70 (12-35) U = 0.451
Y-BOCS (obsession score) 13.00±2.58 (10-16) 13.33±3.15 (7-20) U = 0.866
Y-BOCS (compulsion score) 12.16±3.12 (9-16) 13.75±3.30 (5-17) U = 0.281
Implausible obsessions (yes/no) (4/0) (0/72) χ2(2, n=76) = 76.00, p < 0.001*

Data presented as mean ± standard deviation (range), unless otherwise specified. Categorical data were analyzed with the chi-square test, and non-normally distributed data were analyzed with the Mann–Whitney U test. Differences were considered significant if p < 0.05. OCD = obsessive-compulsive disorder; Y-BOCS = Yale-Brown Obsessive-Compulsive Scale.

More studies on this topic are needed, but taking this feature into account in the conceptualization of obsessions could help professionals in the differential diagnosis between OCD and psychosis, especially in the early stages of psychosis.


1. Jaspers K. General psychopathology. Manchester: Manchester University; 1963. [ Links ]

2. Denys D. Obsessionality & compulsivity: a phenomenology of obsessive-compulsive disorder. Philos Ethics Humanit Med. 2011;6:3. [ Links ]

3. O'Dwyer AM, Marks I. Obsessive-compulsive disorder and delusions revisited. Br J Psychiatry. 2000;176:281-4. [ Links ]

4. Achim AM, Maziade M, Raymond E, Olivier D, Merette C, Roy MA. How prevalent are anxiety disorders in schizophrenia? A meta-analysis and critical review on a significant association. Schizophr Bull. 2011;37:811-21. [ Links ]

Received: April 6, 2015; Accepted: June 18, 2015

Correspondence: E-mail:

Disclosure The author reports no conflicts of interest.

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