The team studied the results of two sleep questionnaires completed by parents within the CHILD-SLEEP birth-cohort, a large study cohort based in southern Finland. For this specific study, the researchers obtained information from nearly 1700 parents who completed a baseline questionnaire, and reported on sleep habits of their children at 3,8, 18 and 24 months. These results were compared with a separate questionnaire on emotional and behavioural symptoms, which was completed by 950 parents at the child´s age of 24 months.