Contrasting Tourette'S Syndrome and TIC Disorders with OCD

The notion of the OCD spectrum has been influential since Hollander (1993) proposed that the unifying factor for several impulsive and compulsive disorders was a difficulty to inhibit or delay involuntary repetitive movement. However, fromthe outset there were difficulties in specifying what exactly defined this continuum. Initially, the continuum ranged from risk avoidance to risk seeking, but in a later publication by Hollander and Benzaquen (1997), the spectrum was viewed as a continuum with overestimation of harm on the compulsive end and underestimation of harm on the impulsive end. The dimension was explicitly conceived within a biological framework of hyper-frontality versus hypo-frontality linked to increased—decreased serotonergic sensitivity. Subsequently, the risk end of the dimension has been labeled variously pleasure seeking, stimulation, and tension reduction. The dizzying array of psychiatric problems now subsumed under the OCD spectrum umbrella suggests that the explanatory power of the spectrum has been gained at the expense of predictive power. However, in order to evaluate the spectrum construct here, I consider it should predict that Tourette's syndrome (TS), chronic motor tic (CMT), and OCD can be classified in different degrees along the same neurobiological, cognitive, and behavioral dimensions. Furthermore, differences in symptomatology should be adequately accounted for by variations along these dimensions.