Some people will say that they have a large number of mental disorders, but they usually have less than they think.

For example, the most common mental disorder is anxiety disorder. However, there are four types of anxiety disorders: post-traumatic stress disorder (PTSD), obsessive-compulsive disorder (OCD), generalized anxiety disorder (GAD) and phobia. Thus even if you feel that you have all four you still have an anxiety disorder. Furthermore, there are sub-sets of the four such as Complex-PTSD or Combat-PTSD. Again, those sub-sets are still one mental disorder--anxiety disorder.