Cognitive processing in obsessive-compulsive disorder: Alternate models and the role of subtypes

This study investigated whether inconsistencies in approaches to cognition in obsessive-compulsive disorder (OCD), summarized as the content versus form models, could be reconciled by the recognition of two recently hypothesized OCD subtypes—Harm Avoidance and Incompleteness—potentially requiring different explanatory frameworks.

A task designed to access cognitive processes predicted by both models was completed by four groups of participants: Harm Avoidance OCD, Incompleteness OCD, nonclinical, and clinical controls. A double-string lexical decision task with semantic priming was employed, with emotional valence and semantic relatedness as manipulated variables. Facilitated lexical decisions for threat words were anticipated in the Harm Avoidance OCD group (i.e., content model). The Incompleteness OCD group alone was expected to display limited semantic priming, irrespective of the emotional valence of stimuli (i.e., form model).

No support was found for the hypotheses. The Harm Avoidance OCD group, like all other groups, exhibited longer lexical decisions for threat words. Although the Incompleteness OCD group displayed less semantic priming than nonclinical controls, so too did the other clinical groups. Unexpectedly, analyses revealed that individuals high in Incompleteness OCD displayed: (1) longer lexical decisions overall than all other groups, (2) longer lexical decisions for dirty than danger-threat words, (3) the longest latencies for nonwords relative to all other lexical stimuli, (4) the greatest increase in decision latencies when nonword primes preceded nonword targets. The Harm Avoidance OCD group, alone among the clinical groups, displayed facilitated decisions for primed danger words.

The findings, though unexpected, were congruent with general predictions. The unique and selective priming of danger words in the Harm Avoidance OCD group implicate threat-congruent processing. The delayed lexical decisions and sensitivity to ambiguous stimuli evidenced in the Incompleteness OCD group are also meaningful: (1) Indecisiveness and doubt may represent an enduring cognitive style, not a symptom-specific response, (2) Intolerance of uncertainty and set-shifting deficits occur at a basic level of processing, and (3) Incompleteness OCD may represent the extreme expression of obsessional personality traits. Thus, characteristics attributed to OCD and thought to distinguish it from other anxiety disorders may be true of only those high in Incompleteness. Clinical, methodological, and theoretical implications are discussed.