The study aims to explore, using indirect ecological measures of exposure, the role of viral infections in the development of anorexia nervosa (AN).

The cohort of participants consisted of all female subjects born in the Veneto region in the period between 1970 and 1984, and residing in the urban and suburban area of Padua (27 682 female subjects in an area of 424 km2). The main outcome measure was the diagnosis of AN resulting from the Public Mental Health Database, the Register of Hospital Admissions, and the Register of the Eating Disorders Unit (n=402, 1.4%). The number of cases of rubella, chickenpox, influenza and measles was ascertained for each month for the 15-year period.

Exposures during the sixth month of pregnancy to the peaks of chickenpox [odds ratio (OR) 1.6, 95% confidence interval (CI) 1.2–2.0] and rubella infections (OR 1.5, 95% CI 1.1–2.0) were significantly associated with an increased risk of developing AN, even after controlling for socio-economic status, urbanization and month of birth. We found weak evidence of a season-of-birth bias.

In utero exposure to viral infection could be a risk factor for developing AN. We need further epidemiological and serological studies to confirm this hypothesis.