PARIS (FRONTLINE MEDICAL NEWS) – One of the most unexpected and intriguing new developments in the field of schizophrenia has to be the discovery that the risk of the disease is significantly increased in men who were diagnosed with inguinal hernia before they were 13 years old.

“I think this is interesting because inguinal hernia in boys has to do with fibroblasts producing abnormal collagen structure,” according to Kristina Melkersson, MD, PhD, who presented her study findings at the annual congress of the European College of Neuropsychopharmacology.

“We don’t know the mechanism behind the relationship between early inguinal hernia and schizophrenia, but there is some connection. It suggests a common biological basis for development of the two disorders,” Dr. Melkersson , a psychiatrist at the Karolinska Institute in Stockholm, said in an interview.

She first detected a signal for a potential relationship in an earlier, small interview study in which she noticed that men with schizophrenia were more likely to have a history of inguinal hernia surgery than did men in the general population. This prompted her to try to confirm this preliminary observation in a large Swedish registry-based cohort study.

Among the nearly 1.3 million Swedes born during 1987-1999, there were 20,705 who were diagnosed with inguinal hernia before age 13 years. During a median 9.9 years of follow-up starting at age 13 years, 1,294 of these individuals were diagnosed with schizophrenia or schizoaffective disorder at a mean age of 21.4 years.

Among men, a history of inguinal hernia diagnosed before age 13 years was associated with a 56% increase in subsequent risk of schizophrenia or schizoaffective disorder, compared with men without such a history.

Women with a history of having inguinal hernia before age 13 years were at 16% increased risk; however, this modest increase in risk was not statistically significant, possibly because of small numbers. Inguinal hernia is 25 times more common in men than women.

Dr. Melkersson reported having no financial conflicts of interest regarding her study, which was supported by a grant from the Swedish Society of Medicine.