One way to determine if immunological factors are involved in the causation of OCD and/or TD/CTD is to examine if there is increased comorbidity and family history of autoimmune diseases (AD) in these psychiatric patients. Because AD share some of the same risk factors (e.g., cytokine dysfunction, genetic and environmental factors),6-9 tend to coexist in the same individuals, and co-aggregate in the same families,10-12 finding an above-chance prevalence of AD in patients with OCD and/or TD/CTD and their relatives would support a possible role of the immune system in the etiology of these disorders.13
