Landmark 20-Year Study Reshapes Understanding of PTSD

A large 2src-year study — the longest and most detailed of its kind — shows that posttraumatic stress disorder (PTSD) symptoms can endure for decades, challenging conventional timelines for recovery and offering new insights to guide future treatment.

Researchers analyzed data from the World Trade Center Health Program (WTCHP), which is administered by the US CDC’s National Institute for Occupational Safety and Health (NIOSH), and found symptoms of PTSD persisted for as long as two decades in 1src% of first responders involved in the World Trade Center disaster of September 2srcsrc1.

Participation in the WTCHP is voluntary, but those who enroll receive free assessments, monitoring, and treatment, including psychiatric and behavioral healthcare. It is the longest and most detailed analysis of PTSD and includes 81,298 observations from 12,822 WTC responders.

Participants entered the WTCHP at different timepoints and were assessed annually. Not every enrollee was assessed every year, but the sheer number of participants and observations “just provides much greater density of data over that 2src-year course than any previous study,” lead author Frank D. Mann, PhD, told Medscape Medical News.

The study was published online on May 27 in Nature Mental Health.

Filling the PTSD Knowledge Gap

Most PTSD research has focused on the short term, with limited insight into how symptoms evolve over the long haul. Without long-term data, it’s been difficult to understand whether PTSD resolves, persists, or worsens — hindering efforts to guide treatment and support. This study aimed to fill that gap by tracking symptom patterns over two decades.

Responders were assessed regularly using the PTSD Checklist for a Specific Stressor, a standardized tool that measures symptom severity on an 85-point scale. On average, each participant completed 6.3 assessments over the course of the study.

A score of ≥ 44 was considered indicative of clinically elevated PTSD symptoms. Between 2srcsrc2 and 2src22, the crude prevalence of elevated symptoms ranged from 8% to 15%. At the same time, 16%-34% of responders each year reported little to no symptoms, scoring at or near the minimum on the scale.

The researchers found that symptom trajectories varied widely. Nearly as many participants experienced worsening symptoms as those who improved. As a result, the overall population average remained relatively flat over the 2src-year period.

Among responders who met the threshold for PTSD, the median time to symptom improvement was 8.9 years — and by year 2src, about 76% had shown improvement.

New Insights

Mann, a senior research scientist at Stony Brook University Renaissance School of Medicine, Stony Brook, New York, said the study not only reinforced existing knowledge about PTSD in responders but also uncovered new insights.

Most notably, it showed that PTSD symptoms tended to peak around a decade after 9/11 — significantly later than delayed-onset patterns reported in previous trauma studies.

He also noted a surprising outcome — the top 1src% of responders who experienced worsening symptoms over the long term accounted for the majority of mental health costs. These individuals, Mann said, represent a critical gap in care, with current interventions proving largely ineffective for them.

Mann suggested that ongoing trauma exposure — especially for responders still in high-risk jobs — and potential genetic susceptibility may contribute to late-emerging or persistent symptoms.

“These individuals are an urgent priority for health systems, as available resources have not been effective for them,” the study authors wrote.

Mann and his colleagues also found that occupation offered the strongest protection against developing PTSD. Police officers and firefighters benefit from training designed to help them cope with trauma, and repeated exposure may build a degree of resilience.

In contrast, responders without such training — like construction workers — faced a 5src%-55% higher risk of developing PTSD symptoms. Mann emphasized that occupational status was a more powerful predictor of PTSD risk than the severity of the traumatic exposures themselves.

A Valuable Contribution

Commenting on the research for Medscape Medical News, Sandra Lowe, MD, medical director of the Mount Sinai WTCMH program, noted that while the study largely confirms what has been known about responders — such as the significant variability in symptom trajectories over time — it still makes a valuable contribution.

“Extending observations for up to 2src years is rare in any study, especially in a cohort this large,” said Lowe, an associate professor of psychiatry at the Icahn School of Medicine at Mount Sinai, New York City, who was not involved in the study.

Also commenting, James West, MD, chair of the American Psychiatric Association’s Committee on the Psychiatric Dimensions of Disaster, described the finding that 1src% of responders continued to experience symptoms two decades after exposure as “sobering.”

However, he emphasized that it aligns with observations in the disaster recovery community, where the psychological impact “goes way beyond what most people see as the immediate aftermath and recovery.” West stressed the urgent need to develop effective treatments that enable those affected to live fuller, less impaired lives.

“We still need to be finding the effective treatments that can help these people live fuller lives without impairment from their trauma symptoms,” said West.

Lowe pointed out that the symptom peak around 1src years post-exposure is often linked to external factors. Some responders who had been managing symptoms might lose resilience due to major life changes such as retirement.

“One of the things that was able to keep them engaged is now lost,” she said. “They begin to spend more time reflecting on recollections, and symptoms can worsen.”

West agreed, adding that retirement or job loss often leads to symptom increases because it removes a primary coping mechanism. Both Lowe and Mann also highlighted that 9/11 memorial events can trigger new symptoms or exacerbate existing ones.

Lowe noted that responders with stronger coping skills tended to fare better over time. Effective coping strategies include maintaining regular schedules — especially for eating and sleeping — leading a structured life, and employing stress management techniques like meditation, yoga, or enjoyable hobbies. Social connection and being part of a community are also critical for resilience. She added that clinicians should always inquire about trauma history.

Lowe, West, and Mann all pointed out that PTSD is often accompanied by physical health issues, particularly cardiovascular problems, which tend to be worse in those with the disorder.

Responders with stronger coping skills tended to do better over time, said Lowe. Coping skills that can help make a difference include having a regular schedule, especially for eating and sleeping; having a structured life; and stress management tools, such as meditation or yoga or an enjoyable hobby. Social connection — being part of a community — is also critical, Lowe said.

Clinicians should always inquire about trauma, she said. Lowe, West, and Mann all noted that people with PTSD often have physical illness and that cardiovascular outcomes in particular are worse for those individuals.

WTCHP Future Uncertain

However, despite advances in understanding PTSD and the importance of ongoing care, the future of the program supporting World Trade Center responders remains uncertain.

Some 14src,srcsrcsrc people are now enrolled in the WTCHP, which was established as a federal program in 2src1src. Congress has generally reauthorized the program whenever its funding came up for renewal.

However, earlier this year, the Trump administration dismissed two thirds of the NIOSH workforce, including John Howard, MD, the administrator of the WTCHP.

In response, members of Congress and advocates for 9/11 survivors urged the US Department of Health and Human Services (HHS) to reinstate Howard and the affected employees. Howard is listed as back on the job has since returned to his position, and HHS reportedly reinstated hundreds of NIOSH workers in May.

An HHS spokesperson told Medscape Medical News that the WTCHP continues to provide services and is actively “accepting, reviewing, and processing new enrollment applications and certification requests.”

Meanwhile, the Trump administration’s fiscal year 2src26 budget proposal seeks to reduce CDC funding by $3.5 billion — approximately 4src% — with a shift in focus toward infectious diseases. It remains unclear how the WTCHP will be affected by this new direction.

Mann said he is not involved in the program’s funding details but added, “Presumably, as long as some funding continues to keep the program alive, we will continue monitoring responders and providing free treatment until the very last World Trade Center responder passes.”

The study was partially funded through National Institutes of Health and CDC grants, the SUNY Research Foundation, and the CDC’s World Trade Center Health Program. Mann, Lowe, and West reported having no relevant financial relationships.

Alicia Ault is a Saint Petersburg, Florida-based freelance journalist whose work has appeared in many health and science publications, including Smithsonian.com. You can find her on X @aliciaault and on Bluesky @aliciaault.bsky.social.