Abstract
There is increasing evidence to suggest that environmental factors are associated with ADHD, but results regarding prenatal maternal stress, unwanted pregnancy, breastfeeding, and ADHD in children are controversial and few prospective studies have been conducted. Using prospectively collected data from the Northern Finland Birth Cohort 1986 (n = 7,910) we studied potential risk factors for ADHD symptoms at 8 and 16 years of age, including prenatal maternal stress and unwanted pregnancy, and protective factors including the duration of breastfeeding. Prenatal stress was associated with an increased risk of ADHD symptoms at the age of 16 (OR = 1.95, 95% CI: 1.34-2.80) and an unwanted pregnancy correlated with hyperactivity symptoms in the offspring at the age of 8 (OR = 2.08, 95% CI: 1.55-2.77). We did not find an association between prenatal maternal stress and hyperactivity symptoms in the offspring at the age of 8 (OR = 0.87, 95% CI: 0.69-1.08) or with unwanted pregnancy and ADHD symptoms at the age of 16 (OR = 1.13, 95% CI: 0.57-2.02). In relation to breastfeeding, over three months of exclusive breastfeeding was associated with lower hyperactivity symptoms in the 8-year follow-up (OR = 0.65, 95% CI: 0.46-0.92) and there was evidence of same kind of relationship concerning non-exclusive breastfeeding, but the association was not statistically significant (OR = 0.76, 95% CI: 0.54-1.06). In 16-year follow-up, under six months of non-exclusive breastfeeding showed an association with ADHD symptoms (OR = 0.68, 95% CI: 0.48-0.95) while exclusive breastfeeding did not (OR = 1.00, 95% CI: 0.66-1.55). In conclusion, our findings suggest that prenatal maternal stress increases the risk of more severe forms of ADHD symptoms in the offspring and breastfeeding can protect against such symptoms at the ages of 8 and 16.