The Committee on Research of the American Neuropsychiatric Association published a systematic review on the neurobiology of the premonitory urge in TS \citep{28121259}. Conceição and colleagues proposed a computational model that attempts to link urge and tic phenomenology with functional anatomical evidence implicating somatosensory cortex and insula \citep{29017141}. An important re-analysis of data from the two large randomized, controlled trials of CBIT found no evidence that reduction in premonitory urge severity mediated improvement in tics \citep{29029679}.
Other
Autism spectrum rating scale scores are elevated in TS \citep{28647013a}. This is mostly but not entirely explained by elevations in the RRB (restricted interests and repetitive behaviors) subscale, which may be indicating tics rather than other stereotypic movements. The presence of OCD was associated with higher scores on the social cognition and RRB subscales.
In a sample of 811 TS subjects recruited for a genetics study, hair pulling (3.8%) and skin picking (13.0%) disorders by DSM-5 were relatively common \citep{29098466}.
Review of screening instruments and rating scales for tic disorders \citep{28071825}, and comments \citep{28436544,28436554}.
A study of 45 children with TS supported the typical antecedent–behavior–consequence behavioral psychology model \citep{27044052}. Specifically, consequences of tics, "such as receiving accommodations or attention from others," explained significantly more variance in tic severity than did the child's level of separation anxiety, though the latter was also a significant factor. This study provides supportive evidence for the approach taken by "CBIT-Jr," a behavior therapy designed for younger children with TS \citep{RN9681}.
Data from 122 adults with TS: "change in symptoms, and treatment response were not associated with neuropsychological performance on tests of inhibitory control, intellectual ability, or motor function, regardless of type of treatment. The finding that significant change in symptom severity of TS/CTD patients is not associated with impairment or change in inhibitory control regardless of treatment type suggests that inhibitory control [as measured by these tests] may not be a clinically relevant facet of these disorders in adults" \citep{27864156}. Sample size or the healthy control group may explain different results from \citet{28039814}.
Etiology
A national database study of parental psychopathology \citep{28335873}.
Genetics
Large mixed genetic sample yielded two heritable collections of symptoms that cross diagnostic boundaries, here named symmetry (including some other O-C symptoms) and disinhibition (including complex verbal tics) \citep{27809572}.
Whole exome sequencing from over 500 trios
\citep{Willsey2017}. Whole exome sequencing in a 3-generation family with TS,
PNKD gene, iPSCs and neuronal cells
\citep{28894297}. News release
here.
Epigenetics
Environmental risk factors