Tourette disorder (TD) is an often-disabling developmental neuropsychiatric syndrome characterized by persistent motor and vocal tics. Onset is typically in early childhood, and estimates of the worldwide prevalence are between 0.3% and 1% (Centers for Disease Control and Prevention, 2009; Robertson, 2008; Scharf et al., 2015). The vast majority of children and adults who present for medical attention have other impairing co-occurring psychiatric disorders, including obsessive-compulsive disorder (OCD) (do Rosário and Miguel Filho, 1997; Ghanizadeh and Mosallaei, 2009; Hounie et al., 2006), attention-deficit/hyperactivity disorder (ADHD) (Burd et al., 2005; Leckman, 2003; Roessner et al., 2007), and mood and anxiety disorders (Cavanna et al., 2009; Hirschtritt et al., 2015). Rates of OCD-like conditions, such as trichotillomania and pathologic skin picking (Lochner et al., 2005), are likewise elevated.
