Longitudinal Impact of Stressors in Adults With Tourette Syndrome

Tourette syndrome (TS) is a widely prevalent neurodevelopmental disorder with limited treatment options,(1,2) substantial impact on quality of life in children(3-7) and adults,(4,8-10) and two-fold increased risk of premature death.(11,12) Tics are the defining feature of TS, and as a result, TS is often narrowly perceived in terms of tics alone. Tics themselves tend to wane in late adolescence, with distressing tics persisting in only one-third of TS patients.(13) Because tics generally diminish with age, the plight of adults with TS is often neglected. Over half of TS adults suffer from anxiety and depression,(10,14) and a similar percentage experience symptoms of attention deficit hyperactivity disorder (ADHD) and obsessive-compulsive disorder (OCD), findings recently corroborated in our own clinical population.(10) Many TS adults struggle to form meaningful relationships with peers, and one-third feel inadequately supported by their families.(13) The burden of TS in adulthood extends beyond mental and social health. In a national registry cohort study, individuals with TS had a mortality rate ratio of 1.8 relative to healthy controls, even after controlling for comorbid psychiatric diagnoses.(11) The causes of more frequent premature death in TS populations are unclear, with many mechanisms implicated, including suicide,(15) traumatic accidents,(12) substance abuse,(16) metabolic disorders,(12,17) and complications from pharmacotherapy.(18,19)

Environmental stressors are also postulated to impact the course of TS.(20) An environmental stressor is any external condition or event that poses a threat to an individual's well-being.(21) Such stressors are known to alter brain development(22-24) and increase risk of adulthood psychopathology.(25,26) A single study has explored the role of environmental stressors in TS, finding that selected stressors predicted two-year tic and psychiatric symptom severity in a pediatric cohort (n=37 patients).(27) No similar investigations have been undertaken in TS adults. The Investigators hypothesize that environmental stressors are risk factors for more severe adult TS phenotype. The Investigators propose a two-year, longitudinal pilot study of TS adults (>18) to determine impact of lifetime environmental stress exposure on tic severity, psychiatric comorbidity severity, and health-related quality of life (HRQOL).

Aim 1. Determine influence of lifetime environmental stressors on tic severity in TS adults. Hypothesis: Number of lifetime stressors at baseline assessment is associated with greater tic severity at two year follow-up. Seventy adults with TS will be recruited from the Vanderbilt TS Clinic to complete a baseline assessment, consisting of validated clinical rating scales for tic severity (Yale Global Tic Severity Scale), common psychiatric comorbidities, and lifetime environmental stressors (Stress and Adversity Inventory for Adults, STRAIN). Because acute and chronic stressors exert differential physiologic and clinical-level effects,(28-31) the STRAIN assesses these separately. The Investigators will use multivariable linear regression to examine the influence of acute and chronic lifetime stressor count at baseline on tic severity at two years, controlling for baseline tic severity and psychiatric comorbidities, as well as anti-tic medications at follow-up. Results will clarify the impact of environmental stressors on tic severity in TS adults.

Aim 2. Determine influence of lifetime environmental stressors on depression in TS adults.

Hypothesis: Number of lifetime stressors at baseline assessment is associated with more depressive symptoms at two-year follow-up. Depression is the psychiatric symptom that most impacts adult functioning and QOL.(10) As part of baseline and follow-up assessments, Aim 1 participants will complete standardized, semi-structured psychiatric interviews (Mini International Neuropsychiatric Interview, MINI) and validated self-report depression scales (NeuroQOL-Depression). The statistical approach from Aim 1 will be adopted to examine the influence of acute and chronic lifetime stressor count at baseline on depression symptom severity at two years, again controlling for select confounds. Findings will delineate the effects of acute and chronic environmental stressors on depression in adults with TS.

Aim 3. Determine influence of positive childhood experiences on health-related quality of life (HRQOL) in TS adults. Hypothesis: Greater number of positive childhood experiences is associated with better HRQOL in TS adults at two-year follow-up. Positive childhood experiences partially mitigate the negative effects of adverse childhood experiences.(32) At baseline and follow-up visits, Aim 1 participants will report number and type of positive childhood experiences. They will also complete a validated HRQOL measure specific to TS: the Gilles de la Tourette-Quality of Life Scale (GTS-QOL). The Investigators will use multivariable regression modeling to examine the influence of positive childhood experiences on future HRQOL, controlling for environmental stressors and baseline HRQOL. Results will elucidate the potentially moderating role of positive childhood experiences on HRQOL in TS adults.