Clinical pharmacology of comorbid attention deficit hyperactivity disorder in Tourette syndrome

Attention deficit hyperactivity disorder (ADHD) is the most common comorbid condition in people with Tourette syndrome (TS), reported in 60-80% of TS clinical samples. The comorbidity between TS and ADHD appears to have a complex pathogenesis and genetic factors can be implicated. Even if the etiological relationship between TS and ADHD is unclear, it is clear that individuals with both TS and ADHD are at a much greater risk for a variety of poor outcomes. It has been largely reported that the presence of comorbid symptoms seems to have a more significant influence on the patient's quality of life than the presence of tics alone, and therefore it can be associated with a major need for pharmacological interventions. Nonpharmacological interventions, including psychotherapy, should be tried in patients with TS and comorbid ADHD before considering pharmacological treatment of ADHD symptoms. Available evidence suggests that the alpha 2-agonists should be the first-line treatment, followed by immediate release or sustained release psychostimulants as second choice, and atomoxetine as third-line treatment. Monitoring of emergence or worsening of tics is particularly recommended during a treatment course of psychostimulants.