We are pleased to share our latest paper in Occupational and Environmental Medicine, reporting findings from the fourth phase of the King’s Centre for Military Health Research Health and Wellbeing Cohort Study.
This is a major piece of work.
The KCMHR Health and Wellbeing Cohort Study has followed UK Armed Forces personnel for more than 20 years. It began in the context of the Iraq and Afghanistan conflicts and has become one of the most important sources of evidence on the health and wellbeing of UK serving and ex-serving personnel.
Our new paper focuses on adverse mental health outcomes and alcohol misuse among personnel who served during this period. It reports findings from Phase 4 of the study, conducted in 2022 and 2023, and builds on earlier phases conducted in 2004–2006, 2007–2009 and 2014–2016.
Why did we do this?
The Iraq and Afghanistan conflicts shaped a generation of UK Armed Forces personnel.
Many of those who served during this period have now left the military, moved into civilian life, built families and careers, and continued to live with the long-term consequences of their service. For others, military service has continued, but against a changing Defence, social and healthcare landscape.
Understanding how this cohort is doing matters.
It matters for Defence. It matters for the NHS. It matters for veterans’ services, military charities, families, researchers, policymakers and, most importantly, for the serving and ex-serving personnel who continue to give their time to take part in this long-running study.
Without long-term cohort research, we are left with snapshots. Snapshots can be useful, but they cannot tell us enough about how health and wellbeing change over time, or how the effects of deployment, service, transition and civilian life can unfold many years later.
What did we do?
For Phase 4, we followed up participants who had taken part in the previous phase of the study in 2014–2016 and had agreed to be contacted again.
In total, 4,104 serving and ex-serving UK Armed Forces personnel completed the survey.
The study examined several key outcomes, including:
- common mental disorders, such as symptoms of anxiety and depression
- probable post-traumatic stress disorder
- complex PTSD
- alcohol misuse
This phase also allowed us to look at how patterns of mental health and alcohol misuse have changed since the previous phase of the cohort.
What did we find?
The majority of participants did not report adverse mental health outcomes or alcohol misuse. That is important. Military service should not be framed only through the lens of harm, and most people in the cohort were not reporting these outcomes.
However, a substantial minority did report difficulties.
Common mental disorders were the most frequently reported outcome, affecting 27.8% of the sample. Probable PTSD was reported by 9.4%, and alcohol misuse by 8.4%.
One of the most striking findings was that most participants who met criteria for probable PTSD also met criteria for complex PTSD. In this study, 72.7% of PTSD cases met the criteria for complex PTSD.
That matters because complex PTSD can involve difficulties beyond core PTSD symptoms, including problems with emotional regulation, relationships and sense of self. This has implications for how people are identified, supported and treated.
We also found that ex-serving Regular personnel had a higher prevalence of probable PTSD and complex PTSD than serving Regular personnel. Among Regular personnel, those whose last deployment to Iraq or Afghanistan was in a combat role also had higher levels of probable PTSD and complex PTSD.
Why does this matter?
The findings show an enduring impact of combat deployment on PTSD among some UK Armed Forces personnel who served during the Iraq and Afghanistan era.
This does not mean that everyone who deployed has poor mental health. That would be inaccurate and unhelpful. The majority remain well.
But the findings do show that a meaningful minority continue to experience mental health difficulties many years after deployment. For some, these difficulties may persist, recur or become more visible during transition out of service.
This has clear implications.
We need continued investment in prevention, early identification and treatment. We need support that recognises the needs of both serving and ex-serving personnel. We need to keep alcohol misuse on the agenda, even where rates appear relatively stable. We also need to understand complex PTSD better in military and veteran populations, including what it means for treatment pathways and long-term support.
A long-term contribution
The strength of this work lies not only in the findings, but in the cohort itself.
Longitudinal research is difficult. It takes time, infrastructure, funding, persistence and trust. It depends on participants continuing to share their experiences over many years. It also depends on a research team able to maintain continuity while adapting to new questions, new measures and new policy priorities.
The KCMHR Health and Wellbeing Cohort Study has done exactly that.
Across four phases, it has provided some of the clearest evidence available on the health and wellbeing of UK Armed Forces personnel who served during the Iraq and Afghanistan conflicts. Phase 4 extends that evidence into the longer-term period after these conflicts, when many personnel have transitioned out of service and when the needs of this cohort may be changing.
What next?
The message from this paper is balanced but important.
Most personnel remain well. However, the long-term mental health needs of those who served during the Iraq and Afghanistan era have not disappeared.
This cohort should not become a forgotten generation.
Research, policy and support services need to continue paying attention to the longer-term effects of military service, combat deployment, transition and alcohol misuse. The evidence from this study can help inform that work.
Read the paper
Sharp ML, Jones M, Franchini S, Leal R, Hull L, Molloy N, Burdett H, Leightley D, Simms A, Stone J, Greenberg N, Murphy D, MacManus D, Wessely S, Stevelink SAM, Fear NT. Adverse mental health outcomes and alcohol misuse among UK Armed Forces personnel: fourth phase of a 20-year cohort study of military personnel who served during the Iraq and Afghanistan conflicts. Occupational and Environmental Medicine. 2026;83(2):70–77. DOI: 10.1136/oemed-2025-110647