What Is PTSD? A Fear Alarm That Stays On After the Danger Ends

Maybe it was months ago, or years. You know you’re safe now. Yet a car door slams, a smell drifts past, or a date comes around on the calendar, and your body reacts as if it’s happening all over again. If that sounds familiar, you’re not overreacting, and you’re not alone.

Your brain is built to learn fear quickly and to unlearn it with precision once danger has passed. That second step, called fear extinction, depends on the hippocampus and the front of your brain teaching the alarm center that a reminder is only a reminder. In a Harvard imaging study, people with post-traumatic stress disorder (PTSD) learned that safety lesson as well as trauma survivors without PTSD, but they had trouble recalling it the next day, with less activity in exactly those regions. The study was small, with 16 people with PTSD and 15 without, but it fits a larger body of imaging research.

The established treatments for PTSD work on that learning process. Trauma-focused therapies like prolonged exposure, cognitive processing therapy, and EMDR, plus SSRI antidepressants, are backed by systematic reviews, and the 2023 VA/DoD guideline gives the leading therapies its strongest recommendation. The results are real, and the science is well established.

But proven PTSD treatment only helps if you can reach it and stay with it, and at Siggy we don’t think the first honest conversation about trauma should be the hardest step in getting care.

This guide explains what PTSD is through the lens of how fear learning works: what’s happening in your brain, how the four symptom groups show up in daily life, who is most at risk, and what the 2023 VA/DoD and 2025 APA guidelines actually recommend. That view of PTSD as a stuck alarm, rather than a flaw in character, comes straight from the biology.

What This Page Covers

• What Is PTSD?
• What Happens in the Brain With PTSD?
• What Are the Symptoms of PTSD?
• Why Do Some People Develop PTSD and Others Don’t?
• How Is PTSD Diagnosed?
• What Treatments Work Best for PTSD?
• Why Are Benzodiazepines Not Recommended for PTSD?
• When Is PTSD an Emergency?
• How Siggy Fits Into PTSD Care
• Say the Hard Part Once, in Your Own Words

What Is PTSD?

PTSD is a mental health condition that can develop after you go through or witness a life-threatening event, such as combat, assault, abuse, a serious accident, or a disaster. Fear and stress after trauma are natural, and most people recover from those reactions over time, NIMH explains. When symptoms last longer than a month and get in the way of relationships or work, it may be PTSD.

It’s common. About 5 in 100 U.S. adults have PTSD in a given year, roughly 13 million people in 2020, according to the National Center for PTSD. Women are more likely than men to develop it.

Trauma itself is even more common. In the WHO’s global surveys across 24 countries, 70.4% of people reported at least one lifetime trauma. Most never develop PTSD. A 2018 trajectory review of 54 studies found that about 65.7% of people followed a resilient path after a potentially traumatic event, 20.8% struggled and then recovered, 10.6% had chronic symptoms, and 8.9% had symptoms that started later.

What Happens in the Brain With PTSD?

Think of your brain’s threat system as a smoke detector with a supervisor. The amygdala is the detector. The medial prefrontal cortex and hippocampus are the supervisors that check context and decide whether there’s actually a fire.

In PTSD, that balance shifts. A 2006 neuroimaging review found heightened amygdala responses in PTSD that tracked with symptom severity, along with a smaller, less responsive medial prefrontal cortex and reduced hippocampal volume and function. The Harvard extinction study found the same pattern in action: the brain regions that help you remember “this is safe now” were less active in people with PTSD.

These changes are measurable, and they help explain why willpower alone rarely shuts the alarm off. They also explain why the most effective therapies work by helping your brain relearn safety, rather than by teaching you to avoid reminders.

What Are the Symptoms of PTSD?

PTSD symptoms fall into four groups, and NIMH’s PTSD guide explains that an adult must have symptoms from every group for at least 1 month, severe enough to interfere with daily life. Here’s how they compare:

Symptom Group	What It Can Feel Like	Needed for Diagnosis
Re-experiencing	Flashbacks, nightmares, intrusive memories	At least 1
Avoidance	Steering clear of places, people, or thoughts	At least 1
Thinking and mood	Guilt, blame, numbness, lost interest	At least 2
Arousal and reactivity	Startling easily, irritability, poor sleep	At least 2

Symptoms usually begin within 3 months of the event, but they sometimes emerge later. The course varies: some people recover within 6 months, while others have symptoms for a year or longer.

What this looks like day to day is often quieter than the movie version. You might stop driving after a crash, keep the TV on so you never sit in silence, snap at people you love, or feel strangely numb at moments that used to bring joy. For more on what sets symptoms off, see our guide to PTSD triggers.

Why Do Some People Develop PTSD and Others Don’t?

The risk isn’t only about how bad the event was. A classic risk factor meta-analysis found that what happens during and after trauma, including its severity, a lack of social support, and additional life stress, had somewhat stronger effects than factors present beforehand.

The type of trauma matters too. The WHO surveys found that traumas involving interpersonal violence carried the highest PTSD risk, and that a history of prior trauma predicted both future trauma exposure and future PTSD. NIMH also lists childhood trauma, being hurt or seeing others hurt, feeling extreme fear or helplessness, and a personal or family history of mental illness as risk factors.

If early experiences are part of your story, our guide to childhood trauma and adult mental health explains how those years can shape stress responses later on.

How Is PTSD Diagnosed?

There’s no blood test or brain scan for PTSD. A clinician makes the diagnosis by asking about the event, your symptoms, how long they’ve lasted, and how they affect your life, often using structured questionnaires. Online self-screens can help you decide whether to ask, but a mental health professional determines whether symptoms meet the criteria, NIMH notes.

A good evaluation also looks for what tends to travel with PTSD. In a 2013 meta-analysis of 57 studies, 52% of people with current PTSD also had major depression. Substance use and anxiety disorders are common too, which is why treating only one piece rarely works.

Some people experience a broader pattern after prolonged or repeated trauma. The World Health Organization’s ICD-11 recognizes complex PTSD, which adds lasting problems with emotional regulation, self-image, and relationships to the core symptoms, as described in a 2022 Lancet review. Our post on complex PTSD vs. PTSD covers the differences.

What Treatments Work Best for PTSD?

Trauma-focused psychotherapy comes first. The 2023 VA/DoD guideline recommends specific manualized psychotherapies over medication, naming prolonged exposure, cognitive processing therapy, and eye movement desensitization and reprocessing (EMDR). It also supports secure video delivery when a therapy has been validated that way or other options aren’t available.

The 2025 APA guideline reaches a similar conclusion: cognitive processing therapy, prolonged exposure, and trauma-focused cognitive behavioral therapy (CBT) show the strongest evidence. Emerging options such as MDMA-assisted therapy and ketamine aren’t yet supported by sufficient evidence.

Medication can help, especially when depression or anxiety is part of the picture. The FDA has approved two SSRI antidepressants for PTSD, NIMH notes, and the VA/DoD guideline recommends paroxetine, sertraline, or venlafaxine. Venlafaxine isn’t FDA approved for PTSD, so it’s prescribed off-label. Here’s how the main options compare under the 2023 VA/DoD guideline:

Treatment	How It Works	Guideline Status
Prolonged exposure	Gradual, safe facing of memories and reminders	Recommended first line
Cognitive processing therapy	Reworks stuck beliefs about the trauma	Recommended first line
EMDR	Memory processing with guided eye movements	Recommended first line
Paroxetine, sertraline, venlafaxine	Antidepressants that ease core symptoms	Recommended medication options
Benzodiazepines	Short-term sedation	Recommended against

NIMH notes that psychotherapy for PTSD usually lasts 6 to 12 weeks but can take longer. Our guides to how PTSD is treated and EMDR therapy for PTSD go deeper on each approach.

Why Are Benzodiazepines Not Recommended for PTSD?

Benzodiazepines such as alprazolam (Xanax) and clonazepam (Klonopin) can quiet anxiety in the moment, so it’s understandable to expect them. But the VA/DoD guideline recommends against using them for PTSD, and a 2015 systematic review concluded they should be considered relatively contraindicated for people with PTSD or recent trauma, with evidence-based PTSD treatments favored instead.

If you already take one, don’t stop on your own. The FDA boxed warning cautions that stopping abruptly or lowering the dose too quickly can cause serious withdrawal reactions, including seizures. Ask your prescriber for a gradual tapering plan.

When Is PTSD an Emergency?

People with PTSD may also experience depression, substance use, or suicidal thoughts, NIMH notes. If you’re having thoughts of suicide, call or text 988 to reach the Suicide and Crisis Lifeline. Veterans can call 988 and press 1. If you or someone else is in immediate danger, call 911.

How Siggy Fits Into PTSD Care

Most people with PTSD carry more than one thing at once: the memories, the sleep they’ve lost, and often depression or anxiety on top. Telling that story to a new clinician can feel like reliving it, and many people dread having to retell their story every time they see someone new.

Siggy’s anonymous intake lets you describe what you’re dealing with in your own words, with no name, email, or account. Siggy’s licensed prescribers diagnose and treat the full range of mental health conditions, including PTSD and complex PTSD, and a prescriber makes every diagnosis and prescribing decision. Siggy’s AI therapy and daily check-ins support the work between visits, and a trauma-focused therapy specialist can be part of the plan. You’ll get a downloadable summary you can share with any clinician, so your story travels with you.

Siggy isn’t an emergency service. If you’re in crisis, call 911 or 988 first. This article is for education only and isn’t a substitute for personal medical advice. It reflects sources available as of October 2026.

Say the Hard Part Once, in Your Own Words

You don’t need to know whether what you’re feeling counts as PTSD before you reach out. Start your anonymous intake and describe the nightmares, the startle, or the numbness at your own pace, without giving your name or email. It’s free, a real doctor reviews anything clinical, and the summary you receive can help a trauma therapist or any clinician pick up where you left off.