There are three main categories of PTSD symptoms, and all three must be present for the diagnosis of PTSD:

reexperiencing the trauma: examples include flashbacks, nightmares, intrusive memories and exaggerated emotional and physical reactions to triggers that remind the person of the trauma.

emotional numbing and avoidance: examples are feeling detached, losing interest and avoiding activities or places that remind you of the trauma.

increased arousal: symptoms like difficulty sleeping, irritability, hypervigilance and exaggerated startle response.