Author Description

Background: Effective health promotion and disease prevention strategies are required to achieve societies where preventable diseases are effectively prevented. Physical activity, diet, alcohol consumption, and tobacco use are all determinants for high-prevalent diseases such as cardiovascular diseases, cancers, chronic respiratory diseases, and diabetes. The cumulative risk of multiple health risk behaviors exceeds the combined risk of each individual behavior. Because health behaviors are formed during childhood and adolescence and occur in clusters that overall affect health, interventions targeting multiple health behaviors in these populations may have a lasting impact on public health. Schools are important for health promotion and disease prevention in children and adolescents. Nevertheless, the literature indicates that school-based interventions that involve school staff to address health-risk behaviors tend to be short-term projects due to barriers that impede long-term implementation. Mobile phones can provide resources for adolescents to promote their health, such as health applications and short text messages that do not rely on school personnel. However, more research is required to better understand whether stand-alone mobile phone-delivered interventions that target multiple health behaviors are a viable way to encourage health-promoting behaviors in adolescents.??Aim: This thesis aims to gain knowledge about health behavior change among Swedish high school students, including the use and effects of an mHealth intervention (LIFE4YOUth) targeting four health behaviors (physical activity, diet, alcohol consumption, and cigarette smoking). The overall aim was addressed through four sub-studies, which specifically aimed to: identify and describe how high school students perceive health behavior change and how mobile phones are used in the process of change (Paper I), explore how high school students understand, interpret, and apply the content of LIFE4YO