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A population-based adult twin study of tics, ADHD and OCD found that the co-occurrence of tics and OCD can be partly explained by shared etiological influences \cite{26919823}. The same is true to some extent for tics and ADHD. Another report concluded that social disinhibition in TS is heritable \cite{27371487}. More research examining sub-dimensions of these phenotypes may clarify the situation.   Another potentially useful approach to TS genetic research was illustrated by \cite{27708560}. This group \citet{27708560}, who  sequenced candidate genes suggested by previous research in order to identify potential functional variants linked to TS. ### Epigenetics