Results
Table 1 presents weighted demographic sample characteristics. Of the students in grades 10 to 12, about 51% were male, 14% were current smokers (17% males and 11% females) and 37% were involved in heavy drinking in the past year. Overall, 78% of high school students experienced at least one injury in the past six months, an average of 2.3 injuries, with male students reported a greater number of injuries relative to female students.
Some variation was observed by injury type. The prevalence of having at least one violence-related injury (25% for males and 12% for females) and transport-related injury (26.3% for males, 11% for females 11%) in the past six months was higher for males than females. Conversely, past six month involvement in unintentional injuries was slightly higher for female students (77.6% vs. 74.8%). Almost one-in-four students had elevated depressive symptoms, with rates for female students (31%) nearly twice that of male students (16%).
Total Number of Injuries (AIC Score)
The crude incidence-rate ratio (IRR) from the negative binomial regression model (not shown) indicates that those with elevated depressive symptoms had 48% more injuries in the past six months (IRR 1.48, 95% CI: 132, 165). The multivariable analyses (Table 2) confirm a positive association between total injuries and elevated depressive symptoms.
Compared to those with minimal depressive symptoms, adolescents with elevated depressive symptoms (IRR 1.41, 95% CI: 1.26, 1.57, Model 1) had 41% more injuries in the past six months. Significant differences in the total number of injuries by covariates were observed: students in grade 10 had 24% (IRR 1.24, 95% CI: 1.11, 1.39) more injuries compared to those in grade 12, while there were positive associations between total number of injuries and being a current smoker (IRR 1.20, 95% CI: 1.04, 1.39), heavy drinking (IRR 1.25, 95% CI: 1.09, 1.42), marijuana use (frequent use: IRR 1.34, 95% CI: 1.18, 1.53; infrequent use: IRR 1.13, 95% CI: 1.01, 1.28, Model 2), sexual activity (multiple sex partners: IRR 1.54, 95% CI: 1.33, 1.78; single sex partner: IRR 1.19, 95% CI: 1.07, 1.32), skipping school 3 days or more (IRR 1.16, 95% CI: 1.01, 1.32) and participation in school team sports (IRR 1.22, 95% CI: 1.11, 1.34). Males had 16% more injuries in the past 6 months (IRR 1.16, 95% CI: 1.06, 1.26) compared to females.
Violence-related Injury
Crude logistic regression results indicate that elevated symptoms of depression were associated with increased odds of experiencing a violence-related injury (Odds Ratio [OR] 2.08, 95% CI: 1.60, 2.71). Multivariable logistic regression results are reported in Table 3 and show that having elevated depressive symptoms increased the odds of having experienced a violence-related injury in the past month (OR 2.21, 95% CI: 1.61, 3.03, Model 1). Also students who: were in grade 10, male, currently smoked, were involved in past year heavy drinking, frequently used marijuana in the past year, were sexually active, had multiple sex partners, and skipped school had an increased odds of reporting a violence-related injury in the past 6 months.
Transport-related Injury
Crude logistic regression results indicate that elevated symptoms of depression were associated with increased odds of experiencing a transport-related injury (OR 1.38. 95% CI: 1.05, 1.82). Multivariable logistic regression results for transport-related injury are reported in Table 4. Again, having elevated depressive symptoms (OR 1.53, 95% CI: 1.10, 2.13) was associated with having experienced a transport-related injury in the past 6 months. Increased odds of reporting transport-related were observed for: males, those who were sexually active, and those who skipped school 3 days or more. Higher academic performance was protective of transport-related injury.
Unintentional Injury
Crude logistic regression results indicate that elevated symptoms of depression were associated with increased odds of experiencing an unintentional injury (OR 1.59, 95% CI: 1.20, 2.11). The multivariable results for unintentional injury are presented in Table 5. As above, elevated depressive symptoms was associated with having experienced at least one unintentional injury in the past 6 months (OR 1.65, 95% CI: 1.20, 2.27). Positive significant associations were also found between unintentional injury and heavy drinking, marijuana use, being sexually active, and participation in school team sports.
Gender Stratification and Injury
Finally, given gender differences in the prevalence of depression, all models were re-run stratifying on gender. Table 6 presents gender-stratified results and reports only associations between elevated depressive symptoms and injury. In terms of total number of injuries, a positive association with having elevated depressive symptoms was similar for male and female students; however, across injury types gender differences were observed. While having elevated depressive symptoms was positively associated with being involved in a violence-related injury for both male (OR 2.10, 95% CI: 1.31, 3.35) and female (OR 2.43, 95% CI: 1.34, 3.38) students, it was associated with transport-related injuries for males only (OR 1.92, 95% CI: 1.22, 3.03), and unintentional injuries for females only (OR 1.81, 95% CI: 1.22, 2.68).