Someone with obsessive–compulsive disorder has intrusive (unwanted) thoughts called obsessions. An unwanted thought is an obsession that will happen many times and is a thought that the person does not want to have. It is normal to have obsessions, but what changes is how people react to the thoughts. People who do not have OCD are able to ignore bad thoughts and move on, and/or such thoughts do not cause them much distress or anxiety. People who have OCD find it very hard to try and ignore these thoughts. However, just because someone has intrusive (unwanted) thoughts does not always mean they have OCD, but it could mean they have something else. Other brain-based disorders that could result in intrusive thoughts include include Bipolar disorder, Depression, Body dysmorphic disorder, and sometimes Attention-deficit hyperactivity disorder (ADHD). 