Post-traumatic stress disorder (PTSD) is a type of anxiety disorder, which can be caused by witnessing or being involved in a very traumatic, distressing or frightening event. PTSD affects people differently. Many people will relive the traumatic event through flashbacks and nightmares leaving them feeling on edge, and perhaps also experiencing guilt, shame or insomnia and, for many, becoming increasingly isolated.
It is common to experience some of the symptoms associated with PTSD after going through a traumatic event. Many people find that these will pass after a few weeks but if the symptoms you are experiencing last longer than a month, a diagnosis of PTSD might be given.