“…Early life risk factors for ADHD span the prenatal period (e.g., pregnancy complications), the perinatal period (e.g., low birth weight, delivery complications), and the early postnatal period (e.g., household poverty, psychosocial adversity) (Das Banerjee, Middleton, & Faraone, 2007;Froehlich et al, 2011;Russell, Ford, Rosenberg, & Kelly, 2014;Sciberras, Mulraney, Silva, & Coghill, 2017;Thapar, Cooper, Jefferies, & Stergiakouli, 2012). These risk factors are assumed to interact with genetic susceptibility and/or to initiate epigenetic processes that lead to disruptions to neural and cognitive development that underlie ADHD (Nigg, 2012a(Nigg, , 2012bThapar, Cooper, Eyre, & Langley, 2013). Virtually all studies that have investigated early life risk factors for ADHD have ignored variations in the age of ADHD symptom onset.…”