deletions | additions       diff --git a/Etiology.md b/Etiology.md  index 8ce8097..6bc910b 100644  --- a/Etiology.md  +++ b/Etiology.md 
...
A collaborative genetic study \cite{26646788} demonstrated an association of TS with 33 genes related to glycolysis or glutamine metabolism. None of the individual genes would have survived correction for multiple testing and the results were consistent with a combined effect of many genetic variants of small effect. These results narrow the hunt for genes that may contribute to the development of TS and they also suggest a new direction for future electrophysiological, imaging and pharmacological studies.  A collaborative genetic study \citep{25735483} demonstrated an association of TS with 33 genes related to glycolysis or glutamine metabolism. None of the individual genes would have survived correction for multiple testing and the results were consistent with a combined effect of many genetic variants of small effect. These results narrow the hunt for genes that may contribute to the development of TS and they also suggest a new direction for future electrophysiological, imaging and pharmacological studies.  \citet{25158072} reported a genome-wide association study (GWAS) from 1,310 people with OCD, 834 with Tourette syndrome, 579 with both OCD and a chronic tic disorder, and over 5,500 controls matched for ancestry. A significant polygenic component was identified for OCD without tics, but not for the combined patient group or other subgroups. Overall, this study is consistent with previous work but provided disappointingly few novel results.  An international study examined tic symptoms in the United States and the Netherlands \cite{25714449}. Three factors were identified: complex vocal tics and obscene behavior, body tics and head/neck tics. Heritability was considered moderate for the first and third factors, h2r=0.21 and 0.25 respectively. Heritability for narrower tic phenotypes is considerably lower than the heritability estimates for frequently comorbid conditions such as OCD and ADHD for which heritability estimates of up to 0.65 have been obtained.