If symptoms last less than three months, the condition is considered acute post-traumatic stress disorder. If symptoms last for at least three months, the disorder is called chronic post-traumatic stress disorder. Acute trauma is a single traumatic event, such as a car accident. Chronic trauma is prolonged or repeated traumatic incidents, such as combat or domestic abuse.
Complex trauma is a combination of acute and chronic trauma, which often occurs in childhood, that alters many aspects of development and of the sense of self. Philip Holcombe is an Army psychologist who serves as head of clinical recommendations at the Deployment Clinical Health Center of the Centers of Excellence in Defense for Psychological Health and Traumatic Brain Injuries. Less research has been done on trauma from a single incident than on chronic trauma, despite evidence that trauma from a single incident still causes complex and significant symptoms and even PTSD in some cases. For example, an isolated incident, such as a car accident, is considered an acute trauma, but ongoing events, such as domestic abuse, can be considered chronic trauma.
Studies show that children exposed to chronic trauma are at greater risk of suffering from mental health disorders, underperforming academically, and becoming juvenile offenders. People are incredibly resilient, and most people who suffer from acute or chronic trauma don't develop PTSD. Symptoms may appear immediately or after a delay, and treatment will vary depending on the individual needs and the person's response. Most people exposed to trauma, acute or chronic, are not diagnosed with a mental health condition such as PTSD.
Studies on mass shootings, a type of acute trauma, have identified risk factors for adverse psychological effects.