Obsessive compulsive disorder (OCD) is a severe and disabling neuropsychiatric condition marked by phenotypic heterogeneity. One way researchers have attempted to overcome this heterogeneity is by identifying dimensions of the disorder based on symptom presentation, which includes groups of obsessions and compulsions that tend to cluster together (1
). Using data from the Yale-Brown Obsessive Compulsive Symptom Checklist (YBOCS-SC; 2
), studies have consistently identified three to six symptom dimensions (3
), including one that has often been termed the “pure obsessional” subtype. Baer (4
) was the first to describe this factor, and found it to be composed of aggressive, sexual, and religious obsessions but no compulsions.
Pinto et al. (5
) developed a more nuanced view of this symptom dimension by dividing those items categorized as “aggressive obsessions” into two categories that represented fears of unintentional harm versus impulsive harm. These two types of aggressive obsessions were associated with different OCD symptom dimensions, with unintentional harm contributing to a Doubt/Checking dimension, and impulsive harm contributing to a dimension termed Taboo Thoughts (sexual, religious, and impulsive aggressive obsessions). This distinction is clinically useful as these domains have been associated with differential treatment responses (7
). However, like the study by Baer, the Taboo Thoughts dimension did not include any compulsions.
The current DSM-IV-TR criteria for OCD assumes a functional relationship between obsessions and compulsions, since compulsions are performed in response to an obsession, but contradictorily allows a diagnosis of OCD to be made if a patient has either obsessions or compulsions (9
). In the DSM-IV field trial, 96% of adults with OCD had both obsessions and compulsions when evaluated by trained raters using the YBOCS-SC, with only 2% having “predominantly obsessions” (10
), which indicates that the pure obsessional type may be less common than indicated by studies of symptoms dimensions. It is possible that this symptom dimension has numerous associated compulsions, but it is not clear exactly which compulsions are factorially associated to “pure obsessions” since prior factor analytic studies tended to omit the many common symptoms categorized as “miscellaneous” in the YBOCS-SC (11
It has been suggested that pure obsessional patients may be experiencing primarily mental rituals. Abramowitz et al. (12
) conducted a category-based cluster analysis, where aggressive, sexual, and religious obsessions were included in a symptom dimension termed Unacceptable Thoughts; mental rituals were the most prominent compulsion associated with that symptom dimension. However, these findings may have been somewhat confounded by the failure to separate the two types of aggressive obsessions described by Pinto et al. (5
). Another notable study was an item-level analysis by Katerberg et al. (13
) using a large sample of participants from sites in the US, Netherlands, and South Africa (N=1,224). A Taboo dimension emerged that included no compulsions, but mental rituals were associated with a dimension termed Rituals and Superstition. The authors note that the heterogeneity of the sample, differential application of the YBOCS-SC items across sites, and lack of inter-rater reliability data may have lead to substantial measurement error; which accounts for why the unusual resulting factor structure may not be the best representation of patients actually seen in clinical practice.
Another ritual that may be connected to the pure obessional profile is compulsive reassurance-seeking. Reassurance-seeking has been recognized as a common behavior among those with OCD (14
), but little research has focused on what types of obsessions are most closely related to this compulsion. Reassurance can be sought from others, or can take the form of a mental ritual as self-reassurance.
Thus prior work has left us unable to answer the clinically and phenomenologically important question: are there specific types of compulsions typically experienced by people previously categorized as pure obsessional? We hypothesize that OCD patients typically considered pure obsessional – those with impulsive aggressive, sexual, and religious obsessions – engage in mental rituals and demands for reassurance. We arrive at this hypothesis because both reassurance-seeking and mental compulsions are fairly common (10
), and the unobservable nature of mental compulsions may cause them to be missed or mistakenly classified as an obsession (12
). The current study examines this issue by factor analyzing a broader set of symptoms than prior studies in a well-characterized clinical sample.