Ross, S. M. (2015). Valerian root and lemon balm extracts: A   phytomedicine compound improves symptoms of hyperactivity, attention deficits,   and impulsivity in children. Holistic Nursing Practice, 29(6), 391–395. https://doi.org/10.1097/HNP.0000000000000118
Phytomedicine using a fixed combination of valerian   (Valeriana officinalis) root extract and lemon balm (Melissa officinalis)   aerial extract. 
The remedy was used to treat various hyperactivity levels,   attention deficits, and impulsiveness in children but not meeting the   criteria according to the DSM-IV for ADHD. Valerian has been shown to improve   sleep disturbances in adults and children. Lemon balm promotes relaxation,   restful sleep and increases attention. Both extracts are made up of over 100   chemicals and the main ingredient being its essential oil component. Children   ages 6 to 11 years were given two tablets of fixed combination phytomedicine   two times per day for seven weeks. The valerian root dosage was 640mg, and   the dosage of lemon balm was 320 mg. The study's results determined that the   children's symptoms were improved considerably, including parental reporting   of intolerable behavior at 58% before treatment and a decrease to 18% after   treatment. Distractibility, morning fatigue, and impulsiveness were symptoms   that were significantly improved. Valerian root may cause headache,   gastrointestinal upset, or insomnia. Lemon balm may cause gastrointestinal   issues, increased appetite, or dizziness (Ross, 2015).
I would be open-minded to phytomedicine usages such as   valerian root and lemon balm for ADHD in young children with precautions.   Many parents prefer the natural route for their children, and I think it is   up to the parents to choose the selected treatment. I would educate the   parents on the side effects and that there is no evidence of either   supplement's long-term effects. It is essential to provide all possible   interventions and complications. I would be open and honest with the family   if I were not educated on the specific type of remedy or disagreed with the   treatment. I would also be hesitant about the interactions with other   supplements and medications. Further research would be beneficial.