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Aim  The aim of this study was to evaluate the impact of pre- and perinatal factors on the risk of developing attention-deficit–hyperactivity disorder (ADHD).

Method  We investigated the medical history of 237 children (206 male; 31 female) from Malmö, Sweden born between 1986 and 1996 and in whom a diagnosis of ADHD (Diagnostic and Statistical Manual of Mental Disorders-IIIR or IV) was subsequently made at the Department of Child and Adolescent Psychiatry, Lund University, and a reference group of 31 775 typically developing children from Malmö using data from the Swedish Medical Birth Register.

Results  The results of multiple logistic regression analysis revealed that ADHD was significantly associated with a young maternal age (odds ratio [OR] for 5y increase 0.87; 95% confidence interval [CI] 0.76–0.99), maternal smoking (OR 1.35; 95% CI 1.14–1.60), maternal birthplace in Sweden (OR 2.04; 95% CI 1.45–2.94), and preterm birth <32 weeks (OR 3.05; 95% CI 1.39–6.71), and a male predominance (OR 6.38; 95% CI 4.37–9.32). Apgar scores at 5 minutes below 7 were significantly associated with ADHD in the univariable analysis (OR 2.60; 95% CI 1.15–5.90). The population-attributable fraction of ADHD caused by the perinatal factors studied was estimated to be 2.8%.

Interpretation  The results indicate that the studied factors constitute weak risk factors for developing ADHD.