To evaluate a possible influence of medication, comparisons were performed between PD patients receiving levodopa, dopamine agonists, catechol‐O‐methyl transferase (COMT) inhibitor, and/or monoamine oxidase type B (MAO‐B) inhibitors versus patients who were treatment‐naïve in relation to the respective drugs. The gene discussed is MAOB; the disease is Parkinson disease.