Adolescence is a critical developmental period in which lifelong health behaviors are shaped, and behaviors acquired during this stage significantly influence health outcomes in adulthood. Physical activity, healthy nutrition, adequate sleep, stress management, and positive social relationships are among the key determinants of adolescent health. However, current evidence indicates that physical inactivity, unhealthy dietary habits, sedentary lifestyles, and psychosocial problems remain highly prevalent among adolescents globally. In addition, insufficient access to health information and inadequate health information-seeking behaviors among adolescents have been reported to be associated with risky health behaviors. Therefore, the development of healthy lifestyle behaviors in adolescents is considered a public health priority.

Schools are recognized as strategic settings for health-promoting interventions targeting adolescents due to their significant social and educational influence on health behaviors. Recent systematic reviews and meta-analyses report that school-based and multi-component interventions have positive effects on adolescents' health behaviors and psychosocial well-being. The integration of behavioral and psychosocial components in school-based health education programs has been associated with more effective and sustainable improvements in adolescent health outcomes . In this process, school health nurses play a critical role in planning and implementing preventive and health-promoting interventions for adolescents . Moreover, it has been reported that healthy behaviors gained through school health nursing interventions may persist into adulthood . Additionally, a systematic review of health education interventions has shown that multi-component approaches-such as classroom education combined with school policies, parental involvement, and school-community collaboration-produce more significant effects on adolescent health outcomes.

In recent years, there has been increasing interest in complementary approaches supporting stress management and emotional well-being in school-based interventions. In this context, laughter yoga is described as a low-cost, feasible, and group-based method associated with reduced stress, improved psychological well-being, and enhanced social interaction. Experimental studies conducted with adolescents have also demonstrated that laughter yoga has positive effects on school burnout, hope, and educational stress. However, the literature indicates a limited number of studies examining the integration of laughter yoga into structured school-based health education programs and its effects on healthy lifestyle behaviors.

In line with the life-course health perspective, school-based interventions aimed at health promotion during childhood and adolescence are reported to be critical for the sustainability of healthy lifestyle behaviors. In this context, the PRECEDE-PROCEED Model is a theoretical framework widely used in the planning and implementation of health promotion programs, systematically assessing behavioral, environmental, and psychosocial factors influencing health behaviors. Studies based on the PRECEDE-PROCEED Model have demonstrated its effectiveness in improving health behaviors among adolescents. Furthermore, current evidence emphasizes that parental involvement in school-based health interventions strengthens the sustainability of behavior change, highlighting the need for further research in this area.

The literature indicates that no studies have examined the effects of a health education program based on the PRECEDE-PROCEED Model integrated with laughter yoga on adolescents' healthy lifestyle behaviors. This gap highlights an important research need for interventions that combine a theoretical behavior change framework with complementary practices that may enhance psychosocial well-being.

Study aim Accordingly, the aim of this study is to evaluate the effect of a health education program based on the PRECEDE-PROCEED Model and integrated with laughter yoga on healthy lifestyle behaviors of secondary school students.

Study hypotheses H1: Students who receive a health education program based on the PRECEDE-PROCEED Model and integrated with laughter yoga will have significantly higher healthy lifestyle behavior scores compared to the control group.

This study is a randomized controlled trial designed to evaluate the effects of a PRECEDE-PROCEED Model-based laughter yoga-supported education program on adolescent health-related behaviors among 8th-grade students in a public middle school in Ankara, Türkiye.

The study was conducted in a socioeconomically disadvantaged district to ensure contextual relevance. A single middle school was selected using simple random sampling, and all eligible 8th-grade students were invited to participate. Participants who met the inclusion criteria and provided parental consent were randomly assigned to intervention and control groups in a 1:1 ratio using computer-generated randomization performed by an independent researcher. Allocation concealment was maintained until assignment. Due to the nature of the intervention, blinding of participants and intervention providers was not possible; however, outcome assessors and data analysts were blinded to group allocation.

The intervention group received a structured 6-week program based on the PRECEDE-PROCEED Model, consisting of weekly health education sessions combined with laughter yoga practices. Health education sessions included interactive materials and visual resources, while laughter yoga sessions were delivered by a certified researcher and included breathing techniques, group exercises, and relaxation activities. Educational materials were also shared with families to support reinforcement outside the school environment. The control group continued with the standard school curriculum and did not receive any intervention during the study period.

Data were collected at three time points: baseline, immediately after the 6-week intervention, and at 3-month follow-up. The intervention's short-term and medium-term effects were evaluated through standardized measurement tools assessing behavioral and psychosocial outcomes. After completion of data collection, a single-session educational activity was offered to the control group for ethical reasons.

Statistical analyses were performed using appropriate parametric and non-parametric tests based on data distribution. Group differences and changes over time were analyzed using repeated-measures approaches, and effect sizes were calculated to determine the magnitude of intervention effects. Statistical significance was set at p < 0.05.

Inclusion Criteria:

• Voluntary participation of the student and parent/guardian
• Being enrolled as an 8th-grade student
• No hearing, visual, or cognitive impairment affecting participation in data collection

Exclusion Criteria:

• Presence of any medical condition contraindicating physical activity
• History of abdominal surgery within the past 3 months
• Diagnosis of diabetes, glaucoma, hypertension, epilepsy, hernia, or asthma