Am J Psychiatry 1995; 152:1646-1651
Copyright © 1995 by American Psychiatric Association
Comorbid Tourette's disorder and bipolar disorder: an etiologic perspective
J Kerbeshian, L Burd and MG Klug
Department of Neuroscience, University of North Dakota School of Medicine, Grand Forks, USA.
OBJECTIVE: Using an epidemiologic approach, the authors attempt to
elucidate relationships between Tourette's disorder and bipolar disorder.
METHOD: Of 205 patients with Tourette's disorder in the North Dakota
Longitudinal Tourette Syndrome Surveillance Project, 15 had comorbid
bipolar disorder. A subset of the patients with Tourette's disorder had
been included in earlier population-based prevalence studies of Tourette's
disorder in children, adolescents, and adults. Minimal risk ratios were
calculated for the patients with Tourette's disorder plus bipolar disorder
by age group (children/adolescents and adults). This information was used
to estimate genetic risk indicators for comorbid Tourette's disorder and
bipolar disorder. RESULTS: The estimated risk of developing bipolar
disorder among the study group of children, adolescents, and adults with
Tourette's disorder was more than four times higher than the level expected
by chance, but this finding did not reach statistical significance. It was
indicative of trends, however. CONCLUSIONS: Comorbidity between Tourette's
disorder and bipolar disorder does not appear to be due to chance
co-occurrence of the two disorders. Although a genetic mechanism may play a
causal role, in the absence of family studies an explanatory model
involving the concept of canalization of basal-ganglia-mediated
dysfunctions is offered. In such a construct, Tourette's disorder would be
a likely accompaniment to other conditions, including bipolar disorder,
whose pathogenic determinants might channel through neural pathways
involving the basal ganglia. The presence of significant developmental
disabilities may further enhance factors culminating in comorbid Tourette's
disorder and bipolar disorder.
