Background Interpreting health information and acquiring health knowledge have become more important with the accumulation of scientific medical knowledge and ideals of patient autonomy. Health literacy and its tremendous success as a concept can be considered an admission that not all is well in the distribution of health knowledge. The internet makes health information much more easily accessible than ever, but it introduces its own problems, of which health disinformation is a major one. Objective The objective of this study was to determine whether objective and subjective health literacy are independent concepts and to test which of the two was associated more strongly with accurate judgments of the quality of a medical website and with behavioral intentions beneficial to health. Methods A survey on depression and its treatments was conducted online (n=362). The Newest Vital Sign was employed to measure objective, performance-based health literacy, and the eHealth Literacy Scale was used to measure subjective, perception-based health literacy. Correlations, comparisons of means, linear and binary logistic regression, and mediation models were used to determine the associations. Results Objective and subjective health literacy were weakly associated with one another (r=0.06, P=.24). High objective health literacy levels were associated with an inclination to behave in ways that are beneficial to one’s own or others’ health (Exp[B]=2.068, P=.004) and an ability to recognize low-quality online sources of health information (β=–.4698, P=.005). The recognition also improved participants’ choice of treatment (β=–.3345, P<.001). Objective health literacy helped people to recognize misinformation on health websites and improved their judgment on their treatment for depression. Conclusions Self-reported, perception-based health literacy should be treated as a separate concept from objective, performance-based health literacy. Only objective health literacy appears to have the potential to prevent people from becoming victims of health disinformation.

BACKGROUND Health knowledge held and health information processed have become more important than ever due to the accumulation of scientific medical knowledge and ideals of patient autonomy. Health literacy and its tremendous success as a concept can be considered an admission that not all is well in the distribution of health knowledge. The Internet makes health information much more easily available than ever, but it introduces its own problems, of which health disinformation is a major one OBJECTIVE To help determine whether objective and subjective health literacy are one or two concepts. To test which of the two is associated more strongly with an adequate judgment of the quality of a medical website and with behavioral intentions beneficial to health. METHODS A survey (n = 362) was conducted online on mental health, and specifically on depression and its treatments. Newest Vital Sign was employed as objective, performance-based measure; the eHealth Literacy Scale as subjective, perception-based. Correlation, comparison of means, linear and binary logistic regression, and mediation models were used to determine the associations RESULTS Objective and subjective health literacy were hardly associated (r = .06, P = .24). High objective health literacy went along with an inclination to behave in ways that are beneficial to one’s own or others’ health (Exp(B) = 2.068, P = .004), and it made people recognize a website of dubious quality for what it is (β = -0.4698, P = .0053). The recognition also improved participants’ preferences for treatment (β = -0.3345, P < .001). Objective health literacy helped people to recognize poor quality in health websites and improved their judgment on the treatment of depression CONCLUSIONS Self-reported and perception-based health literacy should be treated as a different concept from performance-based objective literacy. Only objective literacy appears to have the potential to prevent people from falling for health disinformation