deletions | additions       diff --git a/Etiology.md b/Etiology.md  index 0ac4416..a89b65a 100644  --- a/Etiology.md  +++ b/Etiology.md 
...
### Genetics  A review of genetics of TS appeared [in Frontiers in Neuroscience this July](http://journal.frontiersin.org/article/10.3389/fnins.2016.00351).  Covariation of tics, ADHD and OCD in a population-based adult twin study; co-occurrence of tics and OCD can be partly explained by shared etiological influences (and to some extent tics and ADHD); need more research examining sub-dimensions of these phenotypes \cite{26919823}.  ### Epigenetics