We aim to (1) determine whether a behavioural sleep intervention for children with attention-deficit/hyperactivity disorder (ADHD) leads to sustained benefits; and (2) examine the factors associated with treatment response.

This study was a randomised controlled trial of 244 children (5–13 years) with ADHD from Victoria, Australia. All participants had a moderate/severe sleep problem that met American Academy of Sleep Medicine criteria for an eligible sleep disorder by parent report. The two-session intervention covered sleep hygiene and standardised behavioural strategies. The control group received usual care. Parent- and teacher-reported outcomes at 12 months included sleep, ADHD severity, quality of life, daily functioning, behaviour, and parent mental health. Adjusted mixed effects regression analyses examined 12 month outcomes. Interaction analyses were used to determine moderators of intervention outcomes over time. The trial was registered with ISRCTN, http://www.controlled-trials.com (ISRCTN68819261).

Intervention children were less likely to have a moderate/severe sleep problem by parent report at 12 months compared to usual care children (28.4% v. 46.5%, p = 0.03). Children in the intervention group fared better than the usual care group in terms of parent-reported ADHD symptoms (Cohen's d: −0.3, p < 0.001), quality of life (d: 0.4, p < 0.001), daily functioning (d: −0.5, p < 0.001), and behaviour (d: −0.3, p = 0.005) 12 months later. The benefits of the intervention over time in terms of sleep were less for children not taking ADHD medication and children with parents experiencing depression.

A behavioural sleep intervention for ADHD is associated with small sustained improvements in child wellbeing. Children who are not taking ADHD medication or have parents with depression may require follow-up booster sleep sessions.