Gain-Framed Health Messaging, Medical Trust, and Pre-Exposure Prophylaxis (PrEP) Self-Efficacy: An Experimental Study

<b>Background:</b> Despite the clinical efficacy of pre-exposure prophylaxis (PrEP) in preventing HIV, uptake remains suboptimal among men who have sex with men (MSM) in the United Kingdom (UK). Sustaining progress in the PrEP cascade requires more than biomedical availability; it demands effective, psychologically informed interventions that address persistent barriers. Psychological factors, such as medical mistrust, low PrEP self-efficacy, and identity-related processes, continue to undermine engagement. This study tested whether narrative persuasion and message framing could influence these barriers. <b>Method:</b> A sample of 253 MSM was recruited to participate in an online experiment and completed baseline measures of identity resilience before being randomly allocated to either the gain-framed (<i>N</i> = 122) or loss-framed (<i>N</i> = 124) narrative condition and then completing post-manipulation measures of medical mistrust and PrEP self-efficacy. After excluding 7 cases due to ineligibility, data from 246 participants were analysed using mediation analysis. <b>Results:</b> Participants in the gain-framed condition reported lower medical mistrust than those in the loss-framed condition. Medical mistrust was, in turn, associated with lower PrEP self-efficacy. Identity resilience was associated with lower medical mistrust and higher PrEP self-efficacy. <b>Discussion:</b> These findings provide novel causal evidence that gain-framed health narratives can reduce mistrust and indirectly enhance PrEP self-efficacy. Identity resilience also emerges as a key psychological factor influencing trust and behavioural confidence. <b>Conclusions:</b> Interventions to improve and sustain PrEP uptake should combine gain-framed, narrative-based messaging with strategies to bolster identity resilience. Such approaches may address psychosocial barriers more effectively and promote equitable PrEP uptake among MSM.