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What is posttraumatic stress disorder (PTSD)?

Reviewed by Susan Radzilowski, MSW, LMSW, ACSW

An exhausted medical worker sits and puts her hand to her head

Posttraumatic stress disorder (PTSD) is a mental health disorder that can develop after you witness or experience trauma. Trauma is an emotional response to a terrifying or disturbing event, relationship, or circumstance that threatens or harms your physical, mental, or emotional health and safety. Traumatic events are surprisingly common: In a global survey of nearly 70,000 adults, more than 70% of respondents reported having experienced one.1

Trauma has existed throughout history, but it wasn’t until 1980 that the American Psychological Association (APA) added the term “PTSD” to the third edition of its diagnostic manual, known as the DSM. The APA made this change partly in response to veterans returning from the Vietnam War with a history of trauma—but the new diagnosis covered trauma of all kinds, not just the kind experienced on the battlefield.

Anyone who has experienced trauma can be diagnosed with PTSD, even if they’ve never served in the military or experienced warfare. Research suggests that approximately 6% of people in the US will have PTSD at some point—but not everyone who experiences or witnesses trauma will develop it.2

What causes PTSD?

As the term “posttraumatic” indicates, PTSD develops after someone experiences or witnesses trauma. This sets the disorder apart from other mental health conditions that don’t need an identifiable cause for a diagnosis.

Symptoms of PTSD

To be diagnosed with PTSD following trauma, you must have the following four symptoms for at least a month, and they must affect your ability to function.

  1. Intrusive memories: With PTSD, you unwillingly remember or reexperience your trauma in distressing memories, flashbacks, or nightmares.
  2. Avoidance: With PTSD, you try hard to avoid “triggers”—situations, people, places, thoughts, or memories associated with your trauma.
  3. Cognition/mood changes: PTSD changes the way you think and feel. You may struggle to remember things, even information that isn’t related to your trauma. And you may experience feelings of hopelessness, numbness, or detachment.
  4. Arousal/reactivity: With PTSD, you often feel constantly on guard. This state is called “hypervigilance,” and it can cause insomnia, irritability, anxiety, rapid heartbeat, and muscle tension. You may also respond to stress with irritability, intense guilt and shame, or angry outbursts.

How do PTSD triggers work?

If you have PTSD, certain triggers—sights, smells, sounds, or situations—may remind you of your trauma and cause overwhelming physical or emotional responses (like rapid heartbeat, difficulty breathing, or flashbacks). Your triggers will depend on the trauma you experienced; for example, if you were seriously injured in a car accident, driving may trigger PTSD symptoms.

PTSD triggers don’t have to last forever. Many people learn how to overcome their triggers with professional treatment. Types of therapy that have proven effective for treating PTSD include cognitive behavioral therapy (CBT), exposure therapy, and eye movement desensitization and reprocessing (EMDR). Learn more under “PTSD treatment,” below.

How do you know if you have PTSD?

The only way to be certain you have PTSD is to receive a diagnosis from a mental health professional.

Reactions to trauma

We don’t all respond in the same way after experiencing trauma. Different reactions include:

  • Normal stress response: After an isolated stressor or traumatic event, you may experience symptoms related to the body’s “fight-or-flight” response—like anxiety, increased heart rate, or muscle tension. These effects typically fade shortly after the situation resolves.
  • Acute stress disorder: The symptoms of acute stress disorder (ASD) are similar to PTSD’s—but unlike PTSD, ASD symptoms last for less than a month. If your symptoms continue, your diagnosis may be changed to posttraumatic stress disorder. While some people with ASD develop PTSD, many cases of ASD resolve on their own. (Note that ASD isn’t a type of PTSD, but a separate disorder.)
  • Uncomplicated PTSD: With uncomplicated PTSD, you don’t struggle with additional mental health disorders at the same time. Because of this, your treatment focuses only on addressing your trauma-related symptoms.
  • Comorbid PTSD: Some people with PTSD already struggle with a preexisting mental health disorder, such as anxiety or depression. Others develop a co-occurring mental health condition after they experience trauma. Some of the mental health disorders that happen most frequently alongside PTSD are major depression, anxiety, and substance use disorders.
  • Complex PTSD: Some traumas are single events that affect us dramatically, like a car accident or a natural disaster. Other traumas take place over time, like an abusive relationship or a yearlong deployment to a war zone. If you’ve been through long-term trauma or multiple traumas, you may be diagnosed with complex PTSD.

“Big-T” trauma and “little-t” trauma

Many people wonder, “What counts as trauma?” We often reserve the word for extreme danger or acts of violence. But trauma is all about our response, not the specific events or circumstances themselves. More ordinary situations can still “count” as trauma.

It may be helpful to think about this wider definition in terms of “big-T” and “little-t” trauma. Big-T trauma covers extreme, terrifying, life-altering events and circumstances we already associate with the word “trauma,” such as:

“Little-t” trauma refers to distressing circumstances that are not life-threatening but can still produce a trauma response, like:

Multiple “little-t” traumas can end up affecting our mental health as much as one “big-T” trauma—and multiple “little-t” traumas over the course of a lifetime may result in PTSD.

Experiencing vs. witnessing trauma

It makes sense that if you directly experience trauma, you may develop PTSD. But even simply witnessing trauma can cause PTSD.

Trauma is our response to danger and threats, real or perceived. Even if you were completely safe from the trauma you witnessed, your body may still have reacted to a perceived threat.

First responders, who are tasked with responding to catastrophic events involving severe injury or death, may develop PTSD after witnessing trauma. Children who witness a parent’s violence toward another family member may develop PTSD, even if those children weren’t subject to physical abuse themselves. Even televised national disasters, such as 9/11 or a school shooting, can trigger a trauma response.

What if I don’t remember my trauma?

Trauma affects our cognition, which means you may struggle with memory problems after a traumatic event. You may block your memory of the trauma itself, or you may not even remember having gone through a trauma in the first place.

It’s okay if your memories of a traumatic event are fuzzy or unclear, or if you don’t remember the trauma at all. A therapist can help you unlock those memories safely so you can process them and integrate them into your sense of self.

PTSD treatment

PTSD is treatable, and many people with PTSD benefit greatly from treatment. Below are some of the many options for treating PTSD:

  • Cognitive behavioral therapy (CBT) can help you identify and replace unhelpful thought patterns that fuel your emotions and behaviors. For example, people with PTSD often overestimate the likelihood of bad events happening, and CBT can help counter and address these patterns of thinking.
  • Prolonged exposure therapy allows trauma survivors to relive their trauma in a safe, controlled environment. By confronting your memories and emotions head-on, you can gradually separate fear and anxiety from your traumatic experience and learn how to move forward.
  • Eye movement desensitization and reprocessing (EMDR) therapy allows you to process traumatic memories you may have been blocking. It engages your eyes in a similar way to REM sleep, allowing you to access traumatic memories in a way that helps you make new connections. It can be particularly helpful in recovering memories after trauma.
  • Medication may be prescribed, typically alongside other forms of treatment. Certain antidepressants may help ease some PTSD symptoms.
  • Group therapy with people who’ve survived the same kind of trauma can be a source of support.
  • Animal assistance from a service animal, therapy animal, or emotional support animal may help ease PTSD symptoms.

When should you seek professional help?

Therapy is a great treatment option for PTSD—and you can start going to therapy whenever you want, for whatever reason. It’s a good idea to look for help if you’re struggling with symptoms in the weeks or months after a traumatic event.

If you’re wondering if you have PTSD, you don’t have to figure out whether you meet a certain threshold of trauma or stress on your own. Instead, you can find a therapist with the skills and experience to help you process your memories and emotions—no matter what diagnosis you may or may not receive.

Find a local trauma-informed therapist near you in our provider directory.

Get help now

If you’re in crisis, help is available immediately:

About the author

The editorial team at works with the world’s leading clinical experts to bring you accessible, insightful information about mental health topics and trends.

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