Flashbacks, Nightmares and Triggers

A sound from the street, a date on the calendar, a news report, and the past suddenly feels close. Or you wake at 3 a.m. with your heart pounding and need a minute to work out where you are.

This article explains what clinicians mean by flashbacks, nightmares and triggers, what the VA's National Center for PTSD suggests doing in the moment, and what is known about treatments for nightmares. It does not ask you to think back over what happened to you.

What is a flashback?

A flashback is the sense that the event is happening again now. The VA puts it this way: "You may feel like you are going through the event again. This is called a flashback." The National Institute of Mental Health (NIMH) describes flashbacks as "reliving the traumatic event, including physical symptoms, such as a racing heart or sweating."

Flashbacks belong to a wider group that clinicians call reliving or re-experiencing. The VA says of this group: "Memories of the traumatic event can come back at any time. They can feel very real and scary." Nightmares are part of the same group.

Having flashbacks or nightmares does not by itself mean you have post-traumatic stress disorder (PTSD). PTSD symptoms: what clinicians look for explains how a diagnosis is made.

What is a trigger?

A trigger is a reminder that brings the memory back. The VA's definition: "You may see, hear or smell something that causes you to relive the event. This is called a trauma reminder, cue, or trigger. News reports, seeing an accident, or hearing fireworks are examples of trauma reminders."

Reminders are not only outside you. NIMH says: "Thoughts and feelings can trigger these symptoms, as can words, objects, or situations that are reminders of the event."

A date can be a reminder too. The VA says an anniversary may cue the memory of a traumatic event, and that "it is possible you may not even be aware that there is a connection between your distress and the anniversary of your traumatic event."

Why do reminders set off such strong reactions?

Official sources explain this only in part. Writing about anniversaries, the VA says: "Anniversary reactions may occur because of the way a traumatic experience is saved in memory. Memories of trauma contain information about the danger during the event." It adds: "Sometimes even parts of the memory that seem unrelated can start to signal danger in a way that is unhelpful."

Note the words "may" and "can." These are explanations written for the public, not settled science. The sources behind this article do not go further, so this article does not offer a more detailed mechanism or name parts of the brain.

What can you do during a flashback?

The VA's page on coping with traumatic stress reactions gives these steps:

• "Keep your eyes open. Look around you and notice where you are."
• "Talk to yourself. Remind yourself where you are, what year you're in, and that you are safe. The trauma happened in the past, and you are in the present."
• "Get up and move around. Have a drink of water and wash your hands."
• "Call someone you trust and tell them what is happening."
• "Tell your counselor or doctor about the flashback(s)."

Those are the VA's words, and they assume you are somewhere safe. If you are in danger where you are, call 911.

You may have seen named grounding methods online. The fact-checked sources for this article include no named method in an official guide for patients, so none is given here. The steps above are what the VA's public page describes.

What can you do after a nightmare?

The VA's advice is to place yourself back in the present. When you wake from a nightmare, it says, "remind yourself that you are reacting to a dream." It continues: "You may want to get up out of bed, regroup, and orient yourself to the here and now."

It also says: "Talk to your doctor about your nightmares. Certain medicines can be helpful." The next section explains why that is less simple than it sounds.

Nightmares often come with wider sleep trouble. The VA notes that "People with PTSD may avoid going to sleep." How trauma affects the body covers sleep.

What treatments have been studied for nightmares?

Several have, and expert bodies do not agree about them.

The American Academy of Sleep Medicine (AASM), in a 2018 position paper, recommends image rehearsal therapy for PTSD-associated nightmares and nightmare disorder. The paper describes it as a modified cognitive behavioral therapy technique in which the content of a nightmare is changed and the new version is rehearsed while awake. It is named here so you know what the term means; this article gives no steps for it. The AASM puts the medication prazosin in a lower tier of therapies that "may be used." It downgraded prazosin because of what it calls a contradictory study, which its reference list identifies as the 2018 trial in veterans described below. It also says that many patients respond very well and that prazosin "remains the first choice for pharmacologic therapy."

The 2023 guideline from the Departments of Veterans Affairs and Defense (VA/DoD) rates the same two options the other way round. It says: "We suggest prazosin for the treatment of nightmares associated with PTSD," a weak recommendation, and it describes its confidence in the quality of the evidence as low. It finds insufficient evidence to recommend for or against imagery rehearsal therapy for those nightmares. For PTSD as a whole, the same guideline suggests against prazosin. The American Psychological Association's 2025 guideline on treating PTSD lists both imagery rehearsal therapy and prazosin as having insufficient evidence to recommend for or against.

That 2018 trial, by Raskind and colleagues, found no benefit from prazosin. It was a randomized trial at 13 VA medical centers that assigned 304 veterans with chronic PTSD and frequent nightmares to prazosin or placebo, 152 each. At 10 weeks there were no significant differences between the groups in distressing dreams, sleep quality or overall change. It studied veterans only, and earlier randomized trials had been positive. The VA/DoD guideline, written five years later, says recent systematic reviews still found a benefit for nightmares when this trial was included.

Insufficient evidence means too little good research. It is not a finding that a treatment fails, and it is not an endorsement. Separately, the VA reports that cognitive behavioral therapy for insomnia "reduces how many nightmares people have and the distress related to upsetting dreams."

Whether any medication is right for you is a decision for you and a prescriber. Dr. Rabin is a psychologist and does not prescribe. She can coordinate with a prescriber. Medication, therapy or both for PTSD? has more.

When should you get help?

The VA says to talk to a doctor or mental health care provider if your symptoms last longer than a month, are very upsetting, or disrupt your daily life. It also says only a mental health provider can diagnose PTSD. If you are thinking about harming yourself, call or text 988, or call 911 in an emergency. Veterans, service members and people concerned about them can reach the Veterans Crisis Line by dialing 988 and then pressing 1, or by texting 838255.

For PTSD as a whole, the VA/DoD and American Psychological Association guidelines give their strongest recommendations to specific trauma-focused psychotherapies, such as cognitive processing therapy and prolonged exposure. Psychodynamic therapy has been studied much less for PTSD, and both guidelines list it as having insufficient evidence either way. Types of trauma therapy compares them.

Dr. Rabin offers trauma therapy in Brookline and by secure telehealth across Massachusetts. Her trauma page speaks of intrusive memories, flashbacks and nightmares. Her approach is psychodynamic, attachment-based, trauma-informed and mindfulness-based, and it builds trust and stability before approaching painful material. You decide what is discussed and when. A free consultation of about 15 minutes can be requested through the contact page.

Keep reading

• Do I Need Trauma Therapy?
• Types of Trauma Therapy and What the Research Says
• Do You Have to Talk About What Happened in Trauma Therapy?
• All trauma guides

Sources

• VA National Center for PTSD, PTSD Basics (page header: Last Updated October 2026)
• National Institute of Mental Health, Post-Traumatic Stress Disorder, NIH Publication No. 23-MH-8124 (revised 2023)
• VA National Center for PTSD, Trauma Reminders: Triggers (last updated September 25, 2026)
• VA National Center for PTSD, Trauma Reminders: Anniversaries (last updated September 25, 2026)
• VA National Center for PTSD, Coping with Traumatic Stress Reactions (last updated March 26, 2025)
• VA National Center for PTSD, Sleep Problems and PTSD (last updated September 25, 2026)
• Morgenthaler TI et al., Position Paper for the Treatment of Nightmare Disorder in Adults, full text. J Clin Sleep Med (2018)
• U.S. Department of Veterans Affairs and Department of Defense, VA/DoD Clinical Practice Guideline for Management of Posttraumatic Stress Disorder and Acute Stress Disorder (June 2023)
• Raskind MA, Peskind ER, Chow B et al., Trial of Prazosin for Post-Traumatic Stress Disorder in Military Veterans. N Engl J Med (2018)
• American Psychological Association, Clinical Practice Guideline for the Treatment of Posttraumatic Stress Disorder (PTSD) in Adults (2025)
• U.S. Department of Veterans Affairs, Veterans Crisis Line (accessed 2026)

Last reviewed October 2026. This guide is general information, not medical advice or a diagnosis. If you are in crisis or thinking about harming yourself, call or text 988, or call 911 in an emergency.