ADHD is really common in people with tics: at least 50% of children with tics also have ADHD . What about the other side? I mean, how common are tics in children with ADHD? Until recently, I would have said, “well, more common than in kids without ADHD.” That’s true, but recently I have begun to wonder whether that answer dramatically understates the situation.
Here are the best data we have . Law and Schachar  carried out a careful, randomized controlled trial of methylphenidate for ADHD, lasting 1 year, in 91 children with tics (age 8). They also monitored carefully for tics. Children who at the begining of the study had “a severe motor or vocal tic disorder or Tourette’s disorder,” or who had been treated for tics, were not allowed to participate. Still, mild to moderate tics were observed in 30% of children at the start of the study (27 of 91). During the next year, 12 of the children without tics at the start of the study developed “clinically significant tics for the first time (i.e., moderate or worse).” Importantly, this rate was essentially the same in children on or off methylphenidate—in other words, ADHD is the risk factor, not the stimulant. This study shows that by the end of the study, more than 43% of children with ADHD had tics. We can say “more than” for at least two reasons: first, children with “severe” chronic tics or a history of treatment for tics were excluded from participation, and second, children who developed mild tics for the first time during the year of follow-up are not counted here.
Spencer and colleagues  reported on a large sample of boys with ADHD. 34% had a tic disorder at the start of the study, and 20% of the remaining boys developed tics at follow-up, so that by the end of the study half of the boys (64 of 128) had a current or past tic disorder. (In boys without ADHD, only 10 of 110 had a tic disorder by the end of the study.) The positive news was that tic disorders remitted faster than ADHD did. These diagnoses were based on DSM-III-R, which required impairment in a life role or marked distress to diagnose a tic disorder. Presumably rates would have been even higher if less bothersome tics were counted.
These careful studies suggest that most children with ADHD have tics at some point in their life.
- Cavana AE, Servo S, Monaco F, Robertson MM: The behavioral spectrum of Gilles de la Tourette syndrome. J Neuropsychiatry Clin Neurosci 2009; 21:13-23. PubMed PMID: 19359447 DOI: 10.1176/jnp.2009.21.1.13
- Black KJ, Black ER, Greene DJ, Schlaggar BL: Provisional Tic Disorder: What to tell parents when their child first starts ticcing [version 1; referees: 3 approved]. F1000Res 2016; 5:696. PubMed PMID: 27158458 PubMedCentral PMCID: PMC4850871 DOI: 10.12688/f1000research.8428.1
- Law SF, Schachar RJ: Do typical clinical doses of methylphenidate cause tics in children treated for attention-deficit hyperactivity disorder? J Am Acad Child Adolesc Psychiatry. 1999; 38(8):944-951. PubMed PMID: 10434485 DOI: 10.1097/00004583-199908000-00009
- Spencer T, Biederman M, Coffey B, Geller D, Wilens T, Faraone S: The 4-year course of tic disorders in boys with attention-deficit/hyperactivity disorder. Arch Gen Psychiatry. 1999; 56(9):842-847. PubMed PMID: 12884890