PTSD can develop after individuals experience events that involve actual or threatened serious injury, death, or sexual violence. Symptoms of PTSD can develop related to these experiences if individuals have experienced them directly, witnessed these events happening to others, learned about these events happening to loved ones, or had repeated exposure to the details of these types of events (i.e., first responders, police officers). Common types of traumas that are linked to PTSD symptoms include serious accidents, physical assault or abuse, military combat, natural disasters, terrorist incidents, and sexual assault or abuse.

Individuals with PTSD experience at least some of each of four different types of symptoms:
(1) Intrusive thoughts/feelings related to the trauma, including distressing memories of the trauma, distressing dreams related to the trauma, flashbacks in which the person feels that they are reliving the trauma, and intense physical and/or psychological reactions and distress to cues that are related to the trauma (situations, places, feelings, body sensations, etc.);
(2) Avoidance of things associated with the trauma, including efforts to avoid memories, thoughts and feelings about the trauma, as well as avoiding external reminders of the event (i.e., people, places, objects, talking about the event);
(3) Negative changes in cognition and mood related to the trauma, including difficulties remembering parts of the traumatic event, strong negative beliefs about self/others/the world, feelings of self-blame, negative emotion states (fear, horror, anger, guilt), decreased interest in important activities, feeling detached from others, and difficulties experiencing positive emotions (love, joy);
(4) Changes in physical reactivity/arousal related to the trauma, including increased irritability/anger, exaggerated startle response, hypervigilance, concentration problems, sleep problems, and self-destructive behaviors

Symptoms that persist in each of these categories for more than 1 month following a traumatic event may indicate a diagnosis of PTSD. In some people, symptoms of PTSD do not begin for 6 months or more following a traumatic event. The significant emotional, cognitive, and behavioral changes that can occur with PTSD are often very challenging to live with and can greatly impair functioning and quality of life.