Comorbidities

A survey in children with tic disorders led to a predictive model for "behavioral problems" (based on the CBCL) \citep{36732748}.
\citet{Sadeh2023} examined the presence of depressive symptoms in a cohort of 85 children and adolescents with chronic tic disorders (CTD), aged 6-18 years, with the Child Depression Inventory. In total, 21% had depressive symptoms and the presence of depressive symptoms was correlated with the presence of comorbid OCD and/or ADHD. Furthermore, symptoms of depression moderated the correlation between tic-related impairment and tic severity. Therefore, the authors suggest that it is important to screen and treat depression in children with CTD. 
The presence of depression and anxiety were assessed in several other studies. \citet{Isaacs2023} examined a population of 120 adult patients with CTD with several scales as part of routine care. Symptoms of anxiety were more common than depressive symptoms. Anxiety, depressive and OCD symptom severity were significantly associated to each other, but not to tic severity. In a systematic review and meta-analysis including twelve studies from 1997-2022,  the prevalence of anxiety and depression was found to be 36.4 % and 53.5 % respectively \citep{Abbasi2023}.
Impulsivity and attention were compared in 14 patients with TS, 16 patients with OCD and 28 healthy controls \citep{Koenn2023}. Both patients with OCD and patients with TS showed significant deficits in attention via self-assessment. The severity of tics was correlated strongly positively with attentional impulsivity. The authors conclude that a detailed interpretation of the various tools for measuring impulsive behavior is necessary.
Topic of sleep problems in TS was explored by \cite{Colreavy2023}. Interestingly enough, they found that sleep patterns in children with TS were more impacted by the pandemic than in typically developing children. \cite{Keenan2024} adopted naturalistic, longitudinal approach to examine sleep in children with TS. Importantly, TS children were compared to healthy controls. In addition to clinical assessment, authors attributed variety of scales and measured sleep-wake cycle with wrist actigraphy. As a result, it has been demonstrated that children with TS spent significantly more time in bed, have increased sleep onset latency, reduced sleep efficiency, lower subjective sleep quality, whereas sleep time was comparable. In contrast to clinical observations, self-reported tic severity was not related to increased sleep onset latency. In addition, 83.33% of children with TS fulfilled the diagnostic criteria for a sleep disorder highligting importance for screening for sleep difficulties in clinical routine. 
 
Kurvits et al. \cite{Kurvits2023} investigated investigated the prevalence of prevalence of compulsive sexual behaviors and paraphilic interests in patients with tics. In contrast to previous reports, these comorbidities were found with the same rate as in general population. There was also no association with use of antipsychotics. ADHD was risk factor for paraphilic interests and compulsive sexual behaviors in TS.  
 
TS Study Group from Denmark \cite{Andersen2023} published results of longitudinal study in which correlates of subtance use of pediatric patients with TS. Presence of ADHD and lower socioeconomic status of the guardian predicted higher risk for tobacco smoking, while coexisting OCD was a protective factor. The same group \cite{Tygesen2023} compared fine motor skills in children with TS, their healthy siblings and matched healthy controls. No difference between these three groups were found.
Interesting comorbidity was investigated by researchers from Italy \cite{Prato_2023}
Background: Tourette Syndrome (TS) is a childhood-onset neurodevelopmental disorder with a worldwide prevalence of about 0.3-1% of the population. During the pandemic caused by SARS-CoV-2 infection, the impact on the mental health of children and adolescents was very important. The persistence of symptoms in the post-acute phase of the disease has been termed Long COVID. The neuropsychiatric symptoms seem to be the most common impairment in children and adolescents with long COVID.
Objectives: Considering the impact of pandemic on mental health, in this study we analyzed the long-term effects of SARS-CoV-2 infection in children and adolescents affected by TS.
Methods: We conducted an online questionnaire covering socio-demographic and clinical data among 158 patients affected by TS or chronic tic disorders (CTD), of which 78 participants reported a positive SARS-CoV-2 infection. Data were collected to investigate tic severity and both the comorbidities, as well as lockdown-related changes to daily life activities and, in case of infection of SARS-CoV-2, possible symptoms of acute infection and long COVID. Markers of systemic inflammation including C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), ferritin, iron, electrolytes, white blood cell counts, platelet cell counts levels, markers of liver, kidney and thyroid function were analyzed. First, all patients were screened with the Schedule for affective disorders and Schizophrenia for School age children-present and lifetime (Kiddie-SADS-PL) to rule out primary psychiatric disorders considered as criteria of exclusion. Then, all patients were clinically assessed at baseline (T0), and after three months (T1) through the administration of Yale Global Tic Severity Rating Scale (YGTSS), Multidimensional Anxiety Scale for Children (MASC), Child Depression Inventory (CDI) and Child Behavior Checklist (CBCL).
Results: Among the cohort of TS patients that contracted SARS-CoV-2 infection, 84.6% (n = 66) experienced any acute symptoms, and long COVID symptoms occurred in 38.5% (n = 30). A worsening of clinical symptoms of tics and eventually associated comorbidities occurred in 34.6% (n = 27) of TS patients that contracted SARS-CoV-2 infection. TS patients with or without SARS-CoV-2 infection showed an increase in the severity of tics and also behavioral, depressive and anxious symptoms. Instead, this increase was more evident in patients who contracted the infection than in patients who did not contract it.
Conclusions: SARS-CoV-2 infection may have a role in the increase of tics and associated comorbidities in TS patients. Despite of these preliminary results, further investigations are necessary to improve knowledge about the acute and long-term impact of SARS-CoV-2 in TS patients.