Background: One potential mechanism that could drive differences in outcomes between those with versus without mental illness (MI) and cancer is health literacy (HL). There is limited data on how HL differs according to each condition, and their coexistence.
Methods: This cross-sectional study was conducted using data from the Australian National Health Survey 2017-2018 and HL Survey. We identified all participants aged ≥25 years and categorised them into four groups based on self-reported cancer and MI. Multivariable logistic regressions were performed to examine characteristics associated with MI, with stratification by cancer status. General linear models were used to assess the association between nine individual HL domain scores and cancer and MI.
Results: The study included a total of 15,196 people aged ≥25 years (n=2276, 15% with cancer; n=12,920, 85% without cancer). Of these, nearly one-third of people with cancer (n=690; 30%) and over one-quarter of those without cancer (n=3483; 27%) reported having a MI. Several characteristics were associated with higher odds of MI in both the cancer and non-cancer groups: being female, younger age, obese, current smoker, residing in major cities, having a lower socioeconomic status and physical activity, and a higher number of comorbidities. Odds ratios for these characteristics were generally higher for participants with cancer. MI had significant negative effects on seven individual HL domain scores, while cancer showed significant negative effect on one domain only. There were significant interaction effects between cancer and MI status on two domains that suggested effects were less than additive for subjects with both diagnoses.
Conclusion: Risk factors for MI appeared to be similar in both cancer and general population, although their magnitude differed. HL domains were more strongly associated with MI than cancer. Tailored information for those living with both MI and cancer may help improve outcomes of this vulnerable population.