A technique for influencing the human brain can be applied to treat PTSD through stimulating the brain with a beat in, for example, the theta (θ) frequency to influence the brain to relax. Alternatively, the human brain can be stimulated with a beat in the alpha (α) frequency to stimulate active thinking. Over a series of treatments the brain of an individual suffering from PTSD can be influenced to operate at a normal frequency. Advantageously, as the frequency is adjusted, the symptoms of PTSD recur less often until the individual ceases to experience the symptoms or has at least experienced a decreased recurrence of the symptoms.