Tourette syndrome (TS), also known in the literature as Tourette’s disorder, is a childhood-onset neuropsychiatric disorder that represents one end of a clinical spectrum of developmental tic disorders.1 Tics are recurrent, often sudden, non-rhythmic movements or vocalizations that occur in bursts, and wax and wane over time and body location.
Currently, tic disorders are defined in DSM-5 as distinct categorical entities, including provisional tic disorder (formerly transient tic disorder), persistent (chronic) motor or vocal tic disorder, and Tourette’s disorder.2 Provisional tic disorder is characterized by the presence of motor and/or vocal tics for a period of less than 1 year. Once tics have persisted for more than a year (regardless of whether some have stopped and new ones have begun), persistent (chronic) motor or vocal tic disorder is the appropriate diagnosis. If an individual has a history of only motor, or only vocal tics that have been present for more than 1 year, they would meet criteria for a persistent (chronic) motor tic disorder, or persistent (chronic) vocal tic disorder, respectively.
Based on DSM-5 criteria, Tourette’s disorder is diagnosed when an individual has had two or more motor tics, and at least one vocal tic, over the course of at least 1 year. For diagnostic purposes, it is important to note that motor and vocal tics do not both have to be present for a year, nor do they need to occur simultaneously. Furthermore, DSM-5 criteria specifies that tics may wax and wane in frequency. Individuals may have tic-free periods of weeks to months and many individuals with mild tics do not necessarily notice their presence. Lastly, tic onset must occur prior to age 18, and must not have arisen secondary to, or solely from, an independent medical cause such as encephalitis, exposure to cocaine, or other inherited or degenerative basal ganglia disorders. Tics that onset after age 18 or that fail to meet criteria for either provisional tic disorder, persistent motor or vocal tic disorder, or Tourette’s disorder, are classified as unspecified tic disorder.
While these diagnostic categories are still used both clinically and for research, emerging evidence from multiple types of research studies (clinical, neuroimaging, and genetic) suggest that the diagnostic boundaries between tic disorder categories are likely artificial, and that the group of developmental tic disorders may best be viewed as existing along a continuous phenotypic and developmental spectrum, akin to the unification of Autism Spectrum Disorders in DSM-5 from the prior categories autism, Asperger’s disorder, and pervasive developmental disorder not otherwise specified (PDD-NOS).1,3
Approximately 85% of individuals with TS presenting for clinical evaluation have one or more co-occurring psychiatric conditions.4,5 Although obsessive-compulsive disorder (OCD) and attention-deficit hyperactivity disorder (ADHD) are the two neuropsychiatric conditions most frequently associated with TS, and are thought to have overlapping pathophysiologic mechanisms with TS and related tic disorders,6 almost all major psychiatric ...