Attention deficit/hyperactivity disorder (ADHD) and tic disorders (TD) commonly co-occur. Clarifying the psychiatric comorbidities, executive functions and social adjustment difficulties in children and adolescents of ADHD with and without TD is informative to understand the developmental psychopathology and to identify their specific clinical needs. This matched case-control study compared three groups (n = 40 each) of youths aged between 8 and 16 years: ADHD with co-occurring TD (ADHD + TD), ADHD without TD (ADHD − TD) and typically developing community controls. Both ADHD groups had more co-occurring oppositional defiant disorder than the control group, and the presence of TD was associated with more anxiety disorders. TD did not impose additional executive function impairments or social adjustment difficulties on ADHD. Interestingly, for youths with ADHD, the presence of TD was associated with less interpersonal difficulties at school, compared to those without TD. The potential various directions of effects from co-occurring TD should be carefully evaluated and investigated for youths with ADHD.
Attention-deficit/hyperactivity disorder (ADHD) is a common developmental neuropsychiatric disorder of childhood, with a world-wide pool prevalence of 5.29% (Polanczyk, de Lima, Horta, Biederman, & Rohde, 2007) and a prevalence rate of 7.5% in the Taiwanese child and adolescent population (Gau, Chong, Chen, & Cheng, 2005). ADHD is characterized by early-onset functionally impairing attention deficits, hyperactivity and impulsivity. Commonly occurring together with ADHD, tic disorder (TD) is also an early-onset neuropsychiatric condition, characterized by episodic motor or/and vocal tics. According to the presentation and course of symptoms, it is further classified into Tourette's disorder, chronic tic disorder, transient tic disorder and tic disorder, not otherwise specified. Tourette's disorder shows persistent motor tics and at least one kind of vocal tics persisting for more than one year, with a symptom-free period less than three consecutive months. Chronic tic disorder, a milder form of Tourette's disorder (Leckman et al., 1998), is defined by either motor and/or vocal tics lasting more than one year. Transient tic disorder is defined as having motor and/or vocal tics with a duration of at least four weeks but less than one year. The prevalence is around 5–23% for all tic disorders (Khalifa and von Knorring, 2003, Kurlan et al., 2001 and Wang and Kuo, 2003) and 0.6–3.8% for Tourette's disorder (Hornsey et al., 2001, Khalifa and von Knorring, 2003 and Wang and Kuo, 2003).
TD (including transient/chronic tic disorders and Tourette's disorder) does not add additional executive dysfunctions or social adjustment problems to youths with ADHD, yet the presence of TD is associated with higher co-occurrence of anxiety disorders and less interpersonal relationship difficulties at school. The finer differential patterns of comorbidity, executive functions and social adjustment between ADHD youths with and without TD may imply partially divergent developmental psychopathoplastic processes. In clinical practice and future research for ADHD and related conditions, the potential various directions of effects from co-occurring TD should be carefully evaluated and investigated.
