Familial relationship between Gilles de la Tourette's syndrome, attention deficit disorder, learning disabilities, speech disorders, and stuttering.

Objective: This study examined the familial relationship between Gilles de la Tourette's syndrome (GTS) and attention deficit disorder (ADD), learning problems, speech disorders, and stuttering.

Method: This family study consisted of 338 first degree relatives of 85 GTS probands and 113 controls. All available relatives were personally assessed using structured interviews, and family history information was collected from all family members. Best-estimate diagnoses were assigned for GTS, ADD, learning problems, speech disorders, and stuttering. Analyses examined whether ADD, learning problems, speech disorders, and stuttering by themselves represent genetically variant expressions of GTS.

Results: There was no evidence that ADD, learning problems, speech disorders, or stuttering represent variant expressions of GTS. However, relatives with GTS were at increased risk for ADD regardless of the ADD diagnosis of the GTS proband.

Conclusions: ADD, learning problems, stuttering, and speech problems by themselves are not variant forms of GTS. However, GTS and ADD may be etiologically related in some persons. There may be two types of individuals with GTS and ADD: ones in whom ADD is independent of GTS, and others in whom ADD is secondary to occurrence of GTS.