ILLNESS perceptions preceded increases in functional health literacy difficulties among patients with inflammatory bowel disease (IBD) in a multicentre longitudinal study of 455 patients across nine Italian specialised centres.
The prospective study collected data at baseline, 6 months, and 12 months to examine the longitudinal and reciprocal relationship between perceived functional health literacy and illness perceptions. The analysis specifically distinguished within person changes from stable differences between individuals.
Perceived functional health literacy was assessed using the Single Item Literacy Screener, which measured self-reported difficulty understanding written health information. Illness perceptions were assessed using the Brief Illness Perception Questionnaire. Researchers analysed temporal associations using a Bayesian Random Intercept Cross Lagged Panel Model.
The study addressed an evidence gap identified in previous cross-sectional research, which had suggested an association between functional health literacy and illness perceptions but had not established their temporal direction or separated between person and within person effects.
Worsening illness perceptions were temporally associated with subsequent increases in perceived functional health literacy difficulties. The posterior mean was 0.18, with a 95% credible interval of 0.07–0.28.
The reverse association was not supported by the data. Increases in perceived functional health literacy difficulties did not credibly predict subsequent changes in illness perceptions, with a posterior mean of 0.25 and a 95% credible interval of -0.04–0.53.
Older age, male gender, and Crohn’s disease were stable predictors of both constructs. Perceived functional health literacy also showed strong persistence over time, with β=0.63, whereas illness perceptions demonstrated greater variability and mean reversion, with β=−0.27.
The findings indicate that the relationship between functional health literacy and illness perceptions was asymmetric and driven by within person changes. In particular, deterioration in illness perceptions was followed by greater perceived difficulty understanding written health information, while the reverse temporal pathway was not credible.
The study authors highlighted the potential importance of integrated psychological support in IBD care. The findings suggest that clinicians may need to consider patients’ perceptions of their illness alongside their ability to understand written health information when supporting self-care.
The longitudinal findings provide further insight into how functional health literacy and illness perceptions may change over time in patients with IBD. However, the study identified temporal associations rather than establishing a causal relationship between the two constructs.
Mercuri C et al. Illness perceptions and perceived functional health literacy in inflammatory bowel disease: a multicentre longitudinal study. Sci Rep. 2026;DOI:10.1038/s41598-026-71376-7.
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