context is the key

I wonder if the behavioral effects of ADHD are actually involved in the adaptive advantage, or it is just a side effect of the genetic variation.

Disorder cannot be beneficial. Uncorrected, it becoming disease. Treatment here unusual: remove from the body any substances or drugs, which not intended to be there and let the nature correct all harm, done by our negligence and obscurity. Not mentioning any drugs with their countless side effects and alcohol, think about every day food: cofe, tea, sugar, colas, milk, honey, chocolate... Here is vast field for research, but I am afraid genetic studies in this case would be useless.