The link between autoimmune diseases and obsessive-compulsive and tic disorders: A systematic review.

Immunological factors are increasingly recognized as being important in a range of neuropsychiatric disorders. We aimed to summarize the disperse and often conflicting literature on the potential association between autoimmune diseases (ADs) and obsessive-compulsive disorder (OCD) and tic disorders. We searched PubMed, EMBASE, and PsycINFO for original studies evaluating the relationship between ADs and OCD/tic disorders until July, 13th 2016. Seventy-four studies met inclusion criteria. Overall, the studies were of limited methodological quality. Rates of OCD were higher in rheumatic fever patients who were also affected by its neurological manifestation, Sydenham's chorea. The literature on other ADs was scarce and the findings inconclusive. Few studies examined the association between ADs and tic disorders. A handful of family studies reported elevated rates of ADs in first-degree relatives of individuals with OCD/tic disorders, and vice versa, potentially suggesting shared genetic and/or environmental mechanisms. In conclusion, at present, there is modest evidence for a possible association and familial co-aggregation between ADs and OCD/tic disorders. We offer some suggestions for future research.