A randomised waitlist-controlled trial protocol for examining the efficacy of a nature-based intervention (angling) for military veterans and emergency service personnel with post-traumatic stress disorder (PTSD)

Background Post-traumatic stress disorder (PTSD) is a severely debilitating psychological condition that can affect one’s capacity to work and well-being. Nature-based interventions (NBI) offer a unique avenue for treatment without the typical barriers current psychotherapeutic treatments create for veterans and emergency service personnel (ESP). Data from a pilot study involving military veterans suggests angling as one such NBI, but large-scale robust experimental work is required to assess the causal impact of NBIs. We will therefore conduct a full-scale randomised controlled trial powered to provide definitive evidence of the efficacy of a nature-based, group angling intervention for military veterans and emergency service personnel with PTSD. Methods We will recruit 264 participants for a randomised waitlist-controlled trial of a 2-day, 1-night nature-based angling intervention. We will compare PTSD, anxiety, depression, and wellbeing outcomes between an active and control group. The primary outcome relates to the comparison of pre-intervention (2 weeks before the intervention), with post-intervention measures for the active and control groups taken at 2 and 4 weeks after the intervention. We will also assess if the changes in PTSD scores in the active group might be considered clinically significant and reliable by comparing baseline (2-week pre-intervention) and 2-week and 4-week post-intervention PTSD scores. Secondary outcomes include examining loneliness, expressed anger using baseline and 4-week post-intervention scores. Long-term efficacy will be assessed by 6- and 12-month follow-up surveys. Cost-effectiveness will also be assessed. Process analyses will include examining the contribution of mood change, nature restoration, peer support, and skill learning experiences to the outcomes during the intervention scores at the beginning and end of the intervention. Discussion This randomised controlled trial (RCT) will evaluate the efficacy of a nature-based intervention in reducing PTSD symptoms in military veterans and frontline workers such as emergency service personnel and contribute to the evidence base on the clinical impact of NBIs for mental health outcomes. Trial registration ISRCTN13593648. Registered on 19 June 2024