Post-traumatic stress disorder (PTSD) is a mental health condition that is triggered by a terrifying/traumatic event. Symptoms may include flashbacks, nightmares and severe anxiety, as well as uncontrollable thoughts about the event.
Many people who go through traumatic events have difficulty adjusting and coping for a while. But with time and taking care of oneself, such traumatic reactions usually get better. In some cases, though, the symptoms can get worse or last for months or even years. Sometimes they may completely shake up an individual's life. In a case such as this, one may have post-traumatic stress disorder.
Getting treatment as soon as possible after post-traumatic stress disorder symptoms develop may prevent long-term post-traumatic stress disorder.
Source: mayoclinic.org