ABSTRACT
OBJECTIVES: Contemporary empirical studies have suggested high rates of comorbid attention-deficit hyperactivity disorder(ADHD) or obsessive compulsive disorder(OCD) in children with tic disorders. Not infrequently, ADHD or OCD is as source of greater impairment than are the tic symptoms. The studies in the pathophysiology of tic disorder have implicated abnormalities of dopamine, serotonin and norepinephrine. The studies in pathophysiology of ADHD or OCD also have implicated abnormalities of dopamine, serotonin and norepinephrine. This study was purposed to examine the differences in tic severities and in the levels of plasma homovanillic acid(HVA) and 5-hydroxyin-doleacetic acid(5-HIAA) according to the presence of comorbid ADHD or OCD in patients with chronic tic disorders. METHODS: In fifty chronic tic patients, OCD or ADHD was also diagnosed. And then tic symptoms, obsessive-compulsive symptoms, and attention-deficit hyperactive symptoms were assessed using Yale global tic severity scale(YGTSS), Leyton obsessional inventory-child version(LOI-CV), and Conners parent rating scale. The plasma HVA and 5-HIAA levels were measured using high performance liquid chromatography with electrochemical detection method. RESULTS: Fifty-eight percent of the patients with chronic tic disorders had comorbid ADHD or OCD. But severities of tic did not differ regardless of the presence of comorbid ADHD or OCD. There was a significant positive correlation between tic severities and plasma HVA levels but none between tic severities and plasma 5-HIAA levels. There was a significant inverse correlation between resistance and interference scores and plasma 5-HIAA levels. Plasma HVA levels showed significant positive correlations with plasma 5-HIAA levels. CONCLUSION: These results showed that tic severities didn't vary according to the presence of comorbidities, and that tic severities were correlated with plasma HVA levels, not with plasma 5-HIAA levels. These results suggested that the pathophysiology of chronic tic disorder was strongly correlated with abnormalities of dopaminergic system.