Use of Electronic Cigarettes among Secondary School Students and their Association with Depressive Symptoms: Findings from a National Secondary School Survey in Thailand

Objective: to describe: 1) the prevalence of electronic cigarette use among Thai secondary school students, stratified by grade levels and sex; 2) the extent that depressive symptoms were associated with former and current use of electronic cigarette.Material and Methods: We conducted a cross-sectional study from secondary school students in Thailand in years 7, 9, and 11 of the 12-years educational system. We randomly sampled 113 schools in 21 provinces and Bangkok, randomly sampled classrooms in the school, and invited all students present in the sampled classrooms to participate in the study. All data were collected using self-administered questionnaires. We measured depressive symptoms using the Patient Health Questionnaire-2 (PHQ-2) instrument, and measured electronic cigarette use with adapted versions of existing instruments. Data analyses included descriptive statistics and logistic regression analyses with adjustment for sampling weights.Results: A total of 23,659 students responded and provided adequately completed questionnaires. Approximately 12.3% of the participants reported a lifetime history of using electronic cigarette. Electronic cigarette use was more common among males and older students. There seemed to be a threshold in the association between the level of depressive symptoms and ever vs. never use of electronic cigarette, and the association was strongest at a PHQ-2 score of 6 vs. 0 (adjusted odd ratio (OR)=1.72; 95% confidence interval (CI)=0.98, 3.03). A similar association was found between current vs. former or never use of electronic cigarette and having a PHQ-2 score of 6 vs. 0 (adjusted OR=1.84; 95% CI=0.96, 3.52).Conclusion: We found associations  between depressive symptoms and electronic cigarette use. However, limitations with regard to the lack of temporality, measurement issues, and lack of generalizability should be considered as caveats in the interpretation of the study findings.