In summary, initial treatment with MAO-B inhibitors provides a mild effect on motor symptoms in patients with early PD, delays the need for levodopa, reduces the incidence of motor fluctuations and may furthermore turn out advantageous from a strategic perspective, since it enables physicians to counteract emerging symptoms of early PD without already utilizing the strongest symptomatic options at the very beginning. The gene discussed is MAOB; the disease is Parkinson disease.