Relationships between neuropsychological variables and factor-analysed symptom dimensions in obsessive compulsive disorder.

Despite mounting evidence for the distinctiveness of symptom dimensions in obsessive-compulsive disorder, neuropsychological studies have been few, focused on small samples, and relying on classification of participants based on mutually exclusive symptom categories, resulting in lack of concordance across neuropsychological and imaging studies. Neuropsychological assessment was undertaken with 150 individuals with DSM IV OCD, and neuropsychological variables were analysed in relation to symptom dimension scores derived from factor analysis. Five dimensions were derived from principal components analysis with varimax rotation - contamination/washing, doubts/checking, symmetry/ordering, forbidden thoughts, and hoarding. After controlling for severity of depression and OCD, antipsychotic and benzodiazepine use, and all other symptom dimensions, washing was associated with poorer attention/working memory, visuo-spatial construction and better planning time; checking was related to poorer alternation learning; symmetry linked with poorer verbal fluency; forbidden thoughts with better visuospatial scanning and working memory; hoarding with poorer immediate verbal recall and better visuospatial working memory. The neuropsychological associations are explained in the context of existing neuroimaging evidence, and the clinical picture of each symptom dimension. The use of factor-analysed symptom dimensions and a large sample of individuals with OCD are strengths of the study.