Davids et al (2013) used a study method called genome wide complex trait analysis , which allows simultaneous comparison of genetic variation across the entire genome , rather than the usual method of testing genes one at a time. The genetic datasets of 1500 participants with OCD were compared against 5500 non OCD controls ( the study also compared the data sets of 1500 tourettes syndrome sufferers with 5200 non tourettes controls ). The results showed that both OCD and tourettes syndrome had a genetic basis , though more so in tourettes syndrome , and that although there were some shared genetic characteristics , the two disorders had distinct genetic architectures . This suggests the two are separate disorders , though with some overlap
