There are two main isoforms of MAO: MAO-A, whose inhibition was found useful for many decades in the treatment of depression and anxiety disorders (Livingston and Livingston, 1996), and MAO-B, whose inhibition was found to be beneficial for treating neurodegenerative disorders, including Parkinson’s disease (Cohen, 1990). The gene discussed is MAOB; the disease is depressive symptom measurement.