However, biological studies have shown that "changes in the brain caused by an infection may predispose a person to developing OCD." Another possible cause of OCD is an imbalance or low levels of serotonin. (Causes of Obsessive-Compulsive Disorder, p. 365). There are several ways to treat OCD, one psychological way is cognitive behavioral therapy (CBT). (As stated by Gellatly and Molloy (2014), the goal of CBT is to change or reduce a person's maladaptive behavior. The behavioral method may include “testing irrational thoughts and gradual exposure to feared situations.” (Cognitive Behavioral Therapy p.6) For example, an individual with obsessive compulsive disorder may try to avoid his obsession, then the psychologist may expose him to his obsession cognitive method is used to alter his maladaptive behaviors to change his way of thinking. Methods might be keeping a diary and writing down your inappropriate thoughts and behaviors, when they occur and how often). According to Gellatly and Molloy (2014) an effective CBT for individuals with OCD is exposure and response prevention (ERP). The basis of this therapy is to expose them to their fear, that is, to the thoughts and images that produce their anxiety, in other words their obsession, the therapy gradually exposes them to their obsession, starting first with a situation