Illness perceptions and behavioural responses as mechanisms of change in problem-solving treatment for Veterans with...

Persistent 'medically unexplained' physical symptoms and syndromes (PPS), an umbrella term for symptom-based conditions with poorly understood pathophysiology and aetiology, disproportionately impact Gulf War Veterans. Behavioural interventions are efficacious and recommended as first-line treatments for PPS, but the mechanisms by which these interventions work remain unknown. This study sought to identify mechanisms of change that make problem-solving treatment (PST) efficacious for Veterans living with Gulf War Illness (GWI), a common form of PPS among Veterans who served in Operations Desert Shield/Storm.

Veterans with GWI were randomized to receive either PST or an active control intervention. Analyses focused on the 135 Veterans who were randomized to the PST condition. Outcomes of interest included disability, depressive symptoms, and physical symptoms. Threatening and protective illness perceptions as well as maladaptive and adaptive behavioural responses to illness were analysed as mechanisms of change (i.e., mediators) of these outcomes over time in single-arm mediation models.

All three outcomes were mediated by reduced threatening illness perceptions (p-values .032-.047) and reduced maladaptive behavioural responses (all-or-nothing and limiting responses; p-values .004-.007). Changes in protective illness perceptions and adaptive behavioural responses to illness were not significant mediators of PST outcomes.

Consistent with the cognitive behavioural model of PPS and the Common-Sense Model of Self-Regulation, changes in negative illness perceptions and behavioural responses may act as mechanisms of change in PST for GWI.