Nielsen PR, Benros ME, Dalsgaard S. JAACAP 2017 (March).  Volume 56, Issue 3, Pages 234–240.e1. DOI: http://dx.doi.org/10.1016/j.jaac.2016.12.010

This large Danish study of over 2000 children found that having a history of autoimmune disease increased the risk of developing Attention Deficit and Hyeperactivity Disorder (ADHD) by an incidence rate ratio of 1.24 (95% CI 1.10–1.40).  Having a maternal (but NOT a paternal) history of autoimmune disorder also increased the risk of ADHD by an incidence rate ratio 1.12, 95% CI 1.06–1.19),

http://www.jaacap.com/article/S0890-8567(16)31996-7/fulltext?elsca1=etoc&elsca2=email&elsca3=0890-8567_201703_56_3_&elsca4=Psychiatry%2FAddiction%20Medicine%7CPharmacology%7CPediatrics