There are many scientific studies and controlled studies on using Neurofeedback as a treatment method for various mental disorders. Neurofeedback has been highly successful in the treatment of epilepsy, sleep disorders as well as ADHD and ADD. It has been successfully applied in clinical settings for more than 30 years, particularly in the treatment of ADHD and ADD. Neurofeedback is an evidence-based treatment with proven efficacy as demonstrated in a recent meta-analysis and in this recent review.
A course of Neurofeedback sessions can have the same effect as ongoing intake of psychostimulant medications like Ritalin, for example. The benefit of Neurofeedback, however, is that ongoing treatment is rarely needed after the course length and medications can be avoided altogether.