Most serving and ex-serving personnel did not experience PTSD between 2004–16.

Among those who did meet levels of probable disorder, more worsened or experienced persistent symptoms than improved.

The PTSD classes of serving and ex-serving personnel were similar but more ex-serving personnel had higher levels of symptoms and fewer recovered.

A chronic symptom trajectory, rather than an improving trajectory, was related to low rank and deployment exposures.

New onset PTSD was related to adversities in childhood, deployment exposures and lack of social support.

Whilst most military personnel do not develop Post-Traumatic Stress Disorder (PTSD), ex-serving personnel exhibit higher levels compared to those in service. The heterogeneity of symptom development for serving and ex-serving personnel has not yet been examined in the UK Armed Forces (UK AF). Latent class growth modelling was employed to estimate the trajectories of PTSD symptoms from three waves of data from the PTSD Checklist (PCL-C) from a UK AF sample (N = 7357). Regression mixture models were conducted to investigate covariates of class membership. Five trajectory classes were identified. Most of the sample reported no-low symptoms (71.3%). Of those reporting probable PTSD during the 12 year-period, 4.6% showed improvements, 4.9% worsened, and 1.8% displayed chronic symptoms. A class with subthreshold elevated symptoms (18.2%) was also identified. Trajectories of serving and ex-serving personnel did not differ, but more ex-serving personnel were symptomatic and those with chronic symptoms worsened over time. Chronic disorder was associated with lower rank, experiencing violent combat, and proximity to wounding/death on deployment. Worsening symptoms were associated with childhood stress/violence, lower rank, not being in a relationship, inconsistent post-deployment social support, proximity to wounding/death, and voluntary, or medical discharge. The present study found most UKAF personnel did not report PTSD symptoms between 2004 and 16 but, among those experiencing probable PTSD, more participants reported deteriorating/persistent symptoms than who improved. PTSD-onset was related to adversities across childhood and deployment, and lack of social support. Findings underscore the importance of addressing the through-life contributors of PTSD in order to prevent ingrained disorder.

Cohort study

Post-traumatic stress disorder

Longitudinal data

Latent class

Trajectories

Armed forces

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