Turning order into chaos through repetition and addition of elementary acts in obsessive-compulsive disorder (OCD).

A concept and methodology derived from an animal model provided the framework for a study of rituals in obsessive compulsive disorder (OCD) patients and yielded objective and observable criteria applicable for compulsive rituals across patients. The employed ethological approach should be able to reveal and identify a common structure underlying OCD rituals, pointing to shared psychopathology. Eleven OCD rituals performed by patients in their own home were videotaped and compared with the behaviour of healthy individuals instructed to perform the same rituals. The videotaped rituals were deconstructed into visits to specific locations or objects (ritual space), and to the acts performed at each location/object (ritual basic components). Quantitative analyses revealed that compulsiveness emanates from the expansion of repeats for some acts and visits, and from the addition of superfluous act types. Best discrimination between OCD and control rituals (90.9% success) was provided by the parameter "maximum of act repeats in a ritual" (R(2)=0.77). It is suggested that the identified properties of compulsive behaviour are consistent with a recent hypothesis that ritualized behaviour shifts the individual's attention from a normal focus on structured actions to a pathological attraction onto the processing of basic acts, a shift that invariably overtaxes memory. Characteristics and mechanisms of compulsive rituals may prove useful in objective assessment of psychiatric disorders, behavioural therapy, and OCD nosology.