The Nature of Tic Disorders

Tics are defined, rather vaguely, in the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV; American Psychiatric Association, 1994) nosology as a recurrent, non-rhythmic series of movements (of a non-voluntary nature) in one or several muscle groups. Tics are usually divided into simple and complex tics of a motor, sensory, phonic or cognitive nature. In practice, simple tics have to be differentiated from behaviors such as routines, automatisms and stereotypes; from spasms of neurological or neurochemical origin, and from dystonias and torticollis of a possibly psychoneurological origin. Also, complex tics, which are complex if they involve sequences of several distinct muscle movements, can visibly resemble the ritualized compulsions of obsessive-compulsive disorder (OCD).