Complex post-traumatic stress disorder (CPTSD) is closely related to post-traumatic stress disorder (PTSD). However, it usually develops because of trauma repeated over months or years rather than a single event. Some may forget traumatic events (even if they've experienced them once), relive them in an intrusive way, remember traumatic material in a different chronological order, or other distressing experiences called dissociation. Researchers are still trying to figure out exactly how traumatic stress affects the brain and causes conditions such as CPTSD.
First recognized as a condition affecting war veterans, post-traumatic stress disorder (PTSD) can be caused by a series of traumatic events, such as a car accident, a natural disaster, a near-death experience, or other isolated acts of violence or abuse.