Health literacy refers to the ability of individuals to obtain and understand health risk information using critical thinking about ways in which to prevent disease. According to our studies, there are four components of health literacy: media, science, numeracy, and risk. Critical thinking skills and attitude support these components of health literacy. There are also four steps of critical thinking: clarification, examining the credibility of information, inference, and decision-making. I conducted several surveys among lay people, cancer patients, and the residents who lived both near to and far away from the site of the Fukushima nuclear plant disaster. My results suggested that educational experiences affected critical thinking attitude, which significantly contributed to science, media, risk, and health literacy; this, in turn, improved psychological adaptation to disease or life satisfaction. I will integrate the topics of three speakers and argue the implications of psychological studies for preventive practices in health settings.