The longest military operations in our history began at the turn of this century.

U.S. military forces landed in Afghanistan October of 2001 and in Iraq in March of 2003. Service members from the Army, Navy, Air Force, and Marines engaged in combat operations until withdrawing from Iraq in December 2011 and from Afghanistan in August 2021. Both operations were in direct response to the terrorist attacks that destroyed the World Trade Center in New York City, damaged the Pentagon in Washington D.C., and crashed a commercial airliner in field in Pennsylvania on September 11th, 2001.

Here are some basic facts about the service persons involved in these two conflicts:

  • 3,000,000 military personnel deployed
  • 7,000 killed
  • 53,000 wounded
  • Between 4% and 17% of Iraq/Afghanistan veterans report post-traumatic stress disorder (PTSD)
    • That’s between 120,000 to 510,000 veterans with PTSD

Post-traumatic stress disorder (PTSD) is a serious mental health condition that occurs in response to a traumatic event or events. The disorder can develop in response to a single traumatic event that occurs once – a car accident, a major illness, a single instance of physical/sexual abuse – or it can develop in response to a series of events that occur over time. This second type of PTSD is called complex PTSD and most often develops in the following situations:

  • Victims of ongoing emotional or physical abuse
  • Victims of ongoing sexual abuse
  • Individuals who live in/grew up in war zones
  • Soldiers who spend time in combat and experience multiple, prolonged, traumatic combat-related events, including:
    • Being in combat itself
    • Watching comrades die
    • Deploying lethal force
    • Watching comrades sustain injury
    • Being injured/wounded
    • Experience prolonged shelling/attacks

This article will discuss a new study that examines two approaches to PTSD treatment among combat veterans.

Treatment for Post-Traumatic Stress Disorder Among Veterans: What Works Best?

The paper “Massed vs Intensive Outpatient Prolonged Exposure for Combat-Related Posttraumatic Stress Disorder: A Randomized Clinical Trial,” published in January 2023 in the Journal of the American Medical Association, examined the effect of two different types of an effective, evidence-based treatment for combat PTSD: massed prolonged exposure therapy (massed-PE) and intensive outpatient prolonged exposure therapy (IOP-PE).

Here’s how the researchers framed their primary research question:

Can an intensive outpatient format of prolonged exposure therapy result in larger PTSD reductions than massed outpatient format prolonged exposure therapy?

We’ll explain the difference tween massed outpatient PE therapy and intensive outpatient PE in a moment. First, however, we’ll list the symptoms of PTSD, so that we know and understand why effective treatment for complex PTSD is important, and, in some cases, both life-changing and life-saving.

Symptoms of PTSD

Clinicians divide PTSD symptoms into three primary types: reliving/re-experiencing the initial trauam, hyperarousal, and avoidance.

Reliving or re-experiencing the initial trauma.

Re-living/re-experiencing symptoms include:

  • Flashback
  • Nightmares
  • Unwanted and intrusive thoughts and/or images
  • Extreme emotional and/or physical responses to typical stimuli, including excessive fear, panic, chills, or sweating
  • Increased heart rate in response to memories
  • Hyperventilation in response to memories


An individual in a state of hyperarousal is always on guard and fearful of impending negative events. Hyperarousal symptoms may include:

  • Getting startled or frightened easily
  • Constantly feeling nervous, anxious, or irritable
  • Anger/tantrums
  • Problems with concentration
  • Insomnia


Individuals with avoidant symptoms will do almost anything they can to prevent experiencing anything related to their initial trauma. Avoidant symptoms may include:

  • Self-medication: excess use of substances
  • Spending significant energy avoiding places and people associated with the initial trauma
  • Never talking about the trauma
  • Withdrawing from friends and family
  • Declining interest in new activities
  • Declining participation in daily activities
  • Becoming emotionally distant from others
  • Feeling detached from personal feelings and emotions

In addition, people with PTSD many display the following symptoms:

  • Denial that the trauma occurred
  • Denial that the effect of trauma impacts their life
  • Prolonged, extreme sadness
  • Guilt or shame related to the initial trauma
  • Feelings of hopelessness
  • Suicidal ideation
  • Problems connecting to or discussing emotions
  • Paranoia
  • Difficulty connecting to people and forming new relationships
  • Various physical ailments/pains/somatic problems with no clear medical cause
  • Chronic tiredness/fatigue
  • Chronic pain

Those symptoms show us why it’s critical to find new and effective ways to treat PTSD. Those symptoms can be disruptive and debilitating. In some cases, PTSD can lead to the development of substance use disorder or additional mental health disorders. When this occurs, individuals are at increased risk of suicidal ideation, which can escalate to suicidal behavior, including suicide attempts.

Now let’s get back to that study.

Massed PE Therapy or Intensive Outpatient PE Therapy: Which Works Best for PTSD?

Evidence shows that prolonged exposure therapy can help reduce the most disruptive and uncomfortable symptoms associated with PTSD. Therapists and patients work together on repeated real and imagined exposure to thoughts, images, and places that may trigger symptoms. Slowly, over time, therapists work with patients to address the difficult emotions, memories, thoughts, or circumstances they work hard to avoid. The controlled, repeated exposure to these stimuli gradually reduces the power of those stimuli to trigger symptoms, while simultaneously helping patients build confidence and the belief that they can handle symptoms and situations that previously caused intense distress.

That process is the same for both massed-PE and IOP-PE.Let’s take a look at the differences between the two approaches to PE examined in the study we introduce above:

  • Massed-PE protocol: This contained all the standard elements of PE – real exposure, imaginary exposure, processing techniques – and was delivered in 15 sessions of 90 minutes each over a period of three weeks.
  • IOP-PE protocol: This contained all the standard elements of PE, with the addition of 8 adaptations created for combat veterans. The IOP-PE protocol was also delivered in 15 sessions of 90 minutes each over a period of three weeks.

Now let’s dive into the study, beginning with the characteristics of the study participants:

  • Total: 234 combat veterans
  • Average age: 39
  • Gender:
    • 78% male
    • 22% female
  • Race/ethnicity:
    • 26% African American
    • 25% Hispanic
    • 44% White/Caucasian
    • 3% other

Now for the results.

Treatment completion:

  • 70% of IOP-PE patients completed treatment
  • 77% of massed-PE patients completed treatment
Researchers identified no significant differences between treatment groups for treatment completion.

Symptom reduction:

  • IOP-PE group:
    • One month: Significant symptom reduction on self-reported and clinician-reported metrics
    • Six months: Symptom reduction remained stable on self-reported and clinician-reported metrics
  • Massed-PE group:
    • One month: Significant symptom reduction on self-reported and clinician-reported metrics
    • Six months: Symptom reduction decreased between the on month and six-month check-in for this group
Researchers identified no significant differences between treatment groups for reduction of PTSD symptoms at one month, but found superior reduction of symptoms at the six-month check-in for the IOP-PE group.

PTSD remission:

  • IOP-PE group:
    • One month: 48% of participants were in remission
    • Six months: 53% of participants maintained remission
  • Massed-PE group:
    • One month: 62% of participants were in remission
    • Six months: 53% of participants maintained remission
Researchers identified no significant differences between treatment groups for remission of PTSD according to clinical diagnostic criteria.

Those are promising results. Dr. Alan Peterson, a lead researcher on the study, describe the results in an interview in the online science journal Science Daily:

“We’re excited to see a more than 10-point increase in PTSD remission rates compared to a previous PE study we conducted, when we initiated the first ever clinical trials evaluating PTSD treatments in active-duty military populations.

That’s a major finding – but there’s more.

The Implications of This Research: Intensive Outpatient PE Makes a Difference

This study is important for several reasons.

First, it’s designed to help a demographic who needs our help: our combat veterans. Second, it shows that one of the standard therapies for PTSD, prolonged exposure therapy (PE), is effective for the complex PTSD experienced by combat veterans. Third, it shows that an augmented variation of PE can lead to long-term reductions in PTSD symptoms. Finally, it shows that both massed-PE and IOP-PE show lead to similar rates of remission at six months post-treatment.

Why does IOP-PE show less remission at one month, compared to six months?

Why does massed-PE show less symptom reductions at six months, compared to one month?

Those are questions researchers seek to answer in their next round of clinical trials for these two approaches to treatment for combat-related PTSD. For now, however, we can see these results as a net positive for combat veterans with PTSD: both approaches work, and show significant symptom reduction leading to full remission in over half of the study participants.

For combat veterans who may have experienced PTSD for years – without any relief or symptom reduction – these results offer real hope.

We’ll all Dr. Peterson to have the final word on this good news:

“With about two thirds of participants reporting clinically meaningful symptom improvement and more than half losing their PTSD diagnosis, this study provides important new evidence that combat-related PTSD can be effectively treated – in as little as three weeks.”