Post-traumatic stress disorder is a very common mental illness, with three million Americans having some form of this psychiatric condition. In the 1952 DSM-I, PTSD was named “gross stress reaction.” It has many of the symptoms that fit the present-day description of this condition. In 1980, the diagnosis changed to “Post-Traumatic Stress Disorder” in the DSM-III. The criteria is used to diagnose those who suffer from symptoms such as intrusive memories, avoidance, negative changes in thinking or mood and changes in physical or emotional reactions.