Tourette syndrome (TS) is a neurodevelopmental disorder characterised by both motor and vocal tics. The syndrome’s etiology of the syndrome is not fully understood, although it is known that it has a hereditary component. This study aimed to examine prenatal, perinatal and parental risk factors for TS. Another aim was to validate TS diagnoses in the Finnish Hospital Discharge Register (FHDR).

The study identified all children born between 1991-2010 diagnosed with TS or other tic disorders in the FHDR before 2010. The study was based on nested case-control design, and each case was matched to four controls identified from the Finnish Population Register Center (FPRC). Data were collected from FHDR, Finnish Medical Birth Register (FMBR) and FPRC. Conditional logistic regression analyses were used to used to examine the association between the exposures and TS.

Prenatal maternal smoking was associated with TS when comorbid with Attention deficit/hyperactivity disorder (ADHD). Nulliparity was associated with TS, and increasing parity was associated with decreasing risk for TS/CT (Chronic Tic Disorder). The birth weight of 4000-4499g was associated with a decreased risk for TS. Any maternal and paternal psychiatric diagnoses were associated with an increased risk for TS. However, the association between maternal psychiatric disorders, and TS/CT was stronger than the association between paternal psychiatric disorders and TS/CT, and all maternal-specific diagnostic categories were associated with TS/CT. The validity of the register-based diagnoses in the FHDR was good.

This study identified risk factors associated with TS including nulliparity, parental psychiatric disorders and prenatal maternal smoking when TS is comorbid with ADHD. Further research is needed to elucidate the mechanism of the found associations.