Evidence-based 24-h movement behaviour (24-HMB) guidelines have been developed to integrate recommendations for the time spent on physical activity, sedentary behaviour, and sleep. For children and adolescents, these are a maximum of two hours of recreational screen time (as part of sedentary behaviour), a minimum of 60 min per day of moderate to vigorous physical activity (MVPA), and an age-appropriate sleep duration (9–11 h for 5 to 13-year-olds; 8–10 h for 14 to 17-year-olds). The effects of adhering to the 24-HMB recommendations have not been fully examined in children and adolescents with attention deficit/hyperactive disorder (ADHD). This study examined potential associations between meeting the 24-HMB guidelines and indicators of cognitive and social difficulties in children and adolescents with ADHD. Cross-sectional data on 3470 children and adolescents with ADHD aged between 6 and 17 years was
extracted from the National Survey for Children’s Health (NSCH 2020). Meeting 24-HMB guidelines was associated with reduced likelihood of cognitive and social difficulties in children and adolescents with ADHD. These findings highlight the importance of adhering to healthy lifestyle behaviours as outlined in the 24-HMB recommendations with regard to cognitive and social difficulties in children and adolescents with ADHD.