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.

Symptoms of acute stress disorder are very similar to those of PTSD, with some minor exceptions, and a diagnosis is given if symptoms are present between 3 days and 1 month following a traumatic event.

Many individuals develop emotional or behavior problems following other stressful live events that are not included in the diagnoses of PTSD and acute stress disorder. Examples of these types of stressors include marital problems, a relationship break-up or divorce, job-related difficulties or losing a job, illnesses that lead to increasing levels of disability, living in areas of high crime, etc.