By Michelle Jaffee
Tourette syndrome is more frequently underdiagnosed or diagnosed later in girls compared to boys, according to a new data analysis led by researchers at the University of Florida and Harvard Medical School with international collaborators.
Published Jan. 15 in the journal Neurology, the analysis used the Tourette Association of America International Consortium for Genetics data set to better understand sex differences and health outcomes for the neurodevelopmental disorder.
Researchers examined histories of 2,109 people with Tourette and 294 with persistent motor or vocal tic disorder (PMVT). The two conditions are similar, but people with Tourette have tics that are both motor and vocal — sudden, repetitive, involuntary movements or sounds — while people with PMVT have either motor or vocal tics, but not both types.
Drawing upon a large dataset of people who had volunteered to participate in genetic research on Tourette syndrome and other persistent tic disorders, researchers from UF’s McKnight Brain Institute and Massachusetts General Hospital co-led the multi-institution collaboration.
“We found that these disorders tend to be underdiagnosed in females, potentially leading to delays in appropriate treatment, which can include medication or behavioral therapies or both,” said Carol Mathews, M.D., chair of UF psychiatry and co-author of the study.
“While we’ve known for some time that males are three times more likely than females to have Tourette, PMVT — which is slightly less severe — has a different sex ratio,” Mathews said. “Males are only two times more likely to have PMVT. Yet females continue to be underdiagnosed with both Tourette and PMVT.”
The research team also examined rates of formal clinical diagnosis, severity of tics, and frequency of co-occurring neuropsychiatric disorders such as obsessive-compulsive disorder (OCD) and attention deficit hyperactivity disorder (ADHD).
“We hope this research will alert clinicians to be more aware of the possibility of a persistent tic disorder in both males and females, especially those who have OCD or ADHD,” said Mathews, who directs UF’s Center for OCD, Anxiety & Related Disorders.
Among other key findings:
- Girls with Tourette had lower tic severity and were less likely to have received a formal diagnosis prior to the study (61% compared to 77% for boys).
- On average, it took three years for girls to be diagnosed with Tourette, two years for boys.
- Average age at diagnosis was 13.3 years old for girls and 10.7 for boys.
- Symptom onset of Tourette was slightly later in girls — average of 6½ years old compared to 6 for boys. For PMVT, it was flipped — average of 8.9 years old for boys and 7.9 for girls.
Next steps include delving further into the reasons behind the sex differences as well as examining racial and ethnic differences to ensure results are generalizable.
“We don’t know what the reasons are for the sex differences in the rates of Tourette and PMVT,” Mathews said. “Many potential reasons — from genetic, to hormonal, to environmental — have been discussed, and this is an active area of research.”