This meta-analysis of individual participant data found that behavioural treatments are effective for reducing symptoms of Attention Deficit and Hyperactivity Disorder (ADHD), especially in those with severe symptoms and conduct disorder.

Groenman, A. P., Hornstra, R., Hoekstra, P. J., Steenhuis, L., Aghebati, A., Boyer, B. E., … & van den Hoofdakker, B. J. (2021). An individual participant data meta-analysis: behavioral treatments for children and adolescents with attention-deficit/hyperactivity disorder. Journal of the American Academy of Child & Adolescent Psychiatry.

https://www.jaacap.org/article/S0890-8567(21)00233-1/fulltext?dgcid=raven_jbs_aip_email