Three-year cumulative incidence of diagnosed autism among boys aged 2–4 years, in birth cohorts. Three-year cumulative incidence of diagnosed autism among boys aged 2–4 years, in birth cohorts. Adapted from Hagberg and Jick.16 Promotional and commercial use of the material in print, digital or mobile device format is prohibited without the permission from the publisher Lippincott Williams & Wilkins. Please contact journalpermissions@lww.com for further information. Brent Taylor et al. BMJ Open 2013;3:e003219 ©2013 by British Medical Journal Publishing Group