Table 1 Eligibility criteria

Inclusion criteria

In school Grades 1–4 (age 6–10).

Clinical diagnosis of ADHD combined, predominantly inattentive or predominantly hyperactive-impulsive presentation according to the Diagnostic and Statistical Manual of Mental Disorders, fifth edition (DSM-5)

Written informed consent from parents/legal guardian

Exclusion criteria

IQ <70 as assessed with the Culture Fair Test (CFT) 1-R or the CFT 20-R [44, 45]

Parent-reported diagnosis of the following: serious physical illness or chronic diseases such as pulmonary diseases, heart diseases, diabetes, hypertension, and rheumatic diseases; neurological disorders including stroke, multiple sclerosis, and epilepsy; indicated psychiatric disorders including obsessive-compulsive disorder, chronic tic disorders, Tourette’s syndrome, and suicidal behaviour

Prior or current participation in neurofeedback training (NFT)/biofeedback training (BFT)

Other psychotherapeutic treatment or any kind of attention training, also in the course of an ergotherapeutic treatment, while participating in the study