Using random forest to identify correlates of depression symptoms among adolescents.

PURPOSE: Adolescent depression is a significant public health concern, and studying its multifaceted factors using traditional methods possess challenges. This study employs random forest (RF) algorithms to determine factors predicting adolescent depression scores. METHODS: This study utilized self-reported survey data from 56,008 Canadian students (grades 7-12) attending 182 schools during the 2021/22 academic year. RF algorithms were applied to identify the correlates of (i) depression scores (CESD-R-10) and (ii) presence of clinically relevant depression (CESD-R-10 ≥ 10). RESULTS: RF achieved a 71% explained variance, accurately predicting depression scores within a 3.40 unit margin. The top 10 correlates identified by RF included other measures of mental health (anxiety symptoms, flourishing, emotional dysregulation), home life (excessive parental expectations, happy home life, ability to talk to family), school connectedness, sleep duration, and gender. In predicting clinically relevant depression, the algorithm showed 84% accuracy, 0.89 sensitivity, and 0.79 AUROC, aligning closely with the correlates identified for depression score. CONCLUSION: This study highlights RF's utility in identifying important correlates of adolescent depressive symptoms. RF's natural hierarchy offers an advantage over traditional methods. The findings underscore the importance and additional potential of sleep health promotion and school belonging initiatives in preventing adolescent depression.

Factors associated with prospective changes in weight control intentions among adolescents.

INTRODUCTION: The present study examined predictors of negative changes in weight control intentions from before to during the COVID-19 pandemic among adolescents. METHODS: Participants were Canadian secondary school students enrolled in the COMPASS study and had completed self-report surveys before (T1; 2018/2019 and/or 2019/2020 school year) and during (T2; 2020/2021 and/or 2021/2022) the COVID-19 pandemic (N = 11,869, Mage ± SD = 13.79 years old ± 1.15, 52.89% girls, 45.30% boys, 1.81% gender diverse). Demographic, interpersonal, behavioral, and psychological predictors of weight control intention change from T1 (stay the same weight, not doing anything about weight) to T2 (lose weight, gain weight) were tested using multilevel logistic regressions. RESULTS: Over one-third (37.0%) of adolescents who reported wanting to stay the same weight at T1 changed their intention to lose or gain weight at T2, as did 28.5% of adolescents who reported not wanting to do anything about their weight at T1. Changing weight control intention from "not doing anything about weight" at T1 to weight gain/loss at T2 was associated with resistance training, emotion dysregulation, bullying, social media use, and gender. Changing weight control intention from "stay the same weight" at T1 to weight gain/loss at T2 was associated with gender, perceived financial comfort, social media use, and flourishing. CONCLUSIONS: Results highlight the prevalence of maladaptive weight control intention changes among adolescents, and elucidate related behavioral, interpersonal, demographic, and psychological factors. Findings can inform targeted intervention and prevention strategies to disrupt maladaptive changes in weight control intentions among high-risk subgroups.

The intersection of internalizing symptoms and alcohol use during the COVID-19 pandemic: A prospective cohort study.

Given the well-established relationship between alcohol and internalizing symptoms, potential increases in depression and anxiety during the COVID-19 pandemic may lead to increases in alcohol consumption and binge drinking. This study examines this association from before to during two phases of the pandemic in a cohort of Canadian youth. We used linked data from a sub-sample of 1901 secondary school students who participated in three consecutive school years of the Cannabis use, Obesity, Mental health, Physical activity, Alcohol use, Smoking, and Sedentary behaviour (COMPASS) study between 2018/19 and 2020/21. Separate multilevel logistic regression models examined the association between depression and anxiety symptoms with odds of escalation and reduction (vs. maintenance) and initiation (vs. abstinence) of alcohol consumption. Results show that depression and anxiety symptoms significantly increased over the three years, and these changes were moderated by changes in alcohol consumption and binge drinking. Students with increased depression symptoms were less likely to reduce their alcohol consumption in the early pandemic (Adjust odds ratio [AOR] 0.94, 95% CI:0.90-0.98), more likely to initiate alcohol consumption in the ongoing pandemic period (AOR 1.03, 95% CI: 1.01-1.05), and more likely to initiate binge drinking in both periods. The depression-alcohol use association was stronger among females than males. This study demonstrates a modest association between internalizing symptoms and alcohol use, particularly for depression symptoms and in females. The identified depression-alcohol use association suggests that preventing or treating depression might be beneficial for adolescent alcohol use and vice versa.

Patterns of enteric infections in a population-wide cohort study of sequelae, British Columbia, Canada.

We assessed patterns of enteric infections caused by 14 pathogens, in a longitudinal cohort study of sequelae in British Columbia (BC) Canada, 2005-2014. Our population cohort of 5.8 million individuals was followed for an average of 7.5 years/person; during this time, 40 523 individuals experienced 42 308 incident laboratory-confirmed, provincially reported enteric infections (96.4 incident infections per 100 000 person-years). Most individuals (38 882/40 523; 96%) had only one, but 4% had multiple concurrent infections or more than one infection across the study. Among individuals with more than one infection, the pathogens and combinations occurring most frequently per individual matched the pathogens occurring most frequently in the BC population. An additional 298 557 new fee-for-service physician visits and hospitalisations for enteric infections, that did not coincide with a reported enteric infection, also occurred, and some may be potentially unreported enteric infections. Our findings demonstrate that sequelae risk analyses should explore the possible impacts of multiple infections, and that estimating risk for individuals who may have had a potentially unreported enteric infection is warranted.

Cannabis Use, Screen Time, and Internalizing Symptoms among Canadian Youth: Testing Mediation Pathways.

Background: Existing research suggests positive correlations between screen time sedentary behaviors (STSB) and substance use, including cannabis use, among youth. However, little research has examined what factors mediate these relationships.Methods: This study examined mediating pathways among STSB, internalizing symptoms (IS), and cannabis use in a linked longitudinal sample of 28 269 Canadian youth who participated in the COMPASS study over a two-year period (2017/18 to 2018/19). Structural equation modeling examined two main hypotheses cross-sectionally and over time: 1) if IS mediated associations between STSB and cannabis use frequency, and 2) if STSB mediated associations between IS and cannabis use frequency. Results: Results demonstrated significant partial mediation effects for both hypotheses. For example, indirect effects indicated that IS mediated the association between STSB and cannabis use both cross sectionally (95% CI: 0.021, 0.029) and longitudinally (95% CI: 0.006, 0.010). STSB also mediated associations between IS and cannabis use cross sectionally (95% CI: 0.015, 0.023) and longitudinally (95% CI: 0.010, 0.014). This study demonstrated that the associations between STSB, internalizing symptoms and cannabis use are complex, involving mediation in both directions.Discussion: These findings can be used to inform public health initiatives that aim to take a comprehensive approach to addressing negative health behaviors and outcomes, as it is clear that the multi-directional relationships between STSB and mental health may in-turn impact other health behaviors. Future research should continue to examine mediating factors between STSB and substance use among youth, including exploration of associations with other substances.Supplemental data for this article is available online at https://doi.org/10.1080/10826084.2021.1922455 .

The role of school characteristics in pre-legalization cannabis use change among Canadian youth: implications for policy and harm reduction.

Reducing youth cannabis use in Canada is a public health priority with schools of interest as a potential modifier of behavior and as a venue for prevention programming. This work aimed to provide a basis for future policy and programming by evaluating pre-legalization cannabis use change patterns in schools and the impact of school characteristics on these patterns. Average rates of cannabis use behavior change (initiation, escalation, reduction, cessation) were collected from 88 high schools located in Ontario and Alberta, Canada participating in the COMPASS prospective cohort study. There was little variability in cannabis use behaviors between schools with intra-class correlation coefficients lowest for cessation (0.02) and escalation (0.02) followed by initiation (0.03) and reduction (0.05). Modest differences were found based on school province, urbanicity and student-peer use. Cannabis ease of access rates had no significant effect. Fewer than half the schools reported offering school drug use prevention programs; these were not significantly associated with student cannabis use behaviors. In conclusion, current school-based cannabis prevention efforts do not appear sufficiently effective. Comprehensive implementation of universal prevention programs may reduce cannabis harms. Some factors (urbanicity, peer use rates) may indicate which schools to prioritize.

An Examination of Bidirectional Associations Between Alcohol Use and Internalizing Symptoms Among Adolescents During the COVID-19 Pandemic.

PURPOSE: This study explores the bidirectional association between internalizing symptoms and alcohol use over three years of the COVID-19 pandemic to examine whether alcohol consumption is associated with higher internalizing symptoms in the next year and vice versa. METHODS: We used linked data from a sample of 2,136 secondary school students who participated in three consecutive waves (2019-2020 [T1], 2020-2021 [T2], and 2021-2022 [T3]) of the Cannabis use, Obesity, Mental health, Physical activity, Alcohol use, Smoking, and Sedentary behaviour study during the pandemic. A random-intercept cross-lagged panel model was used to characterize reciprocal linear relations between internalizing symptoms and alcohol use. RESULTS: The findings suggest that students who reported higher levels of alcohol use at T1 experienced increased levels of depression and anxiety in the subsequent year (T2). However, this association was not observed from T2 to T3. Throughout the three-year period, depression and anxiety were not associated with later alcohol use. In males, alcohol use at T1 was a predictor of higher internalizing symptoms at T2 but not from T2 to T3. DISCUSSION: These results suggest time-sensitive impacts and notable gender differences in the relationship between internalizing symptoms and alcohol use over the pandemic. Given the complexity of impacts, ongoing evaluation of the impact of the pandemic on youth health behaviours is necessary to elucidate these unfolding relationships, especially as the pandemic continues to affect various psychosocial risk factors.

Inequitable Changes in School Connectedness During the Ongoing COVID-19 Pandemic in a Cohort of Canadian Adolescents.

BACKGROUND: We examined whether subgroups of adolescents experienced disparate changes in school connectedness-a robust predictor of multiple health outcomes-from before the COVID-19 pandemic to the first full school year following pandemic onset. METHODS: We used 2 waves of prospective survey data from 7178 students attending 41 Canadian secondary schools that participated during the 2019-2020 (T1; pre-COVID-19 onset) and 2020-2021 (T2; ongoing pandemic) school years. Fixed effects analyses tested differences in school connectedness changes by gender, race, bullying victimization, socioeconomic position, and school learning mode. RESULTS: Relatively greater declines in school connectedness were reported by students that identified as females, were bullied, perceived their family to be less financially comfortable than their classmates, and attended schools in lower income areas. Marginally greater school connectedness declines resulted among students attending schools that were fully online at T2 than those at schools using a blended model. CONCLUSION: Results point to disparate school connectedness declines during the pandemic, which may exacerbate pre-existing health inequities by gender and socioeconomic position, and among bullied youth. IMPLICATIONS FOR SCHOOL HEALTH POLICY, PRACTICE, AND EQUITY: Effective strategies to improve school climates for equity denied groups are critical for pandemic recovery and preparedness for future related events.

Adolescents' Depression and Anxiety Symptoms During the COVID-19 Pandemic: Longitudinal Evidence From COMPASS.

PURPOSE: There is concern over the potentially detrimental impact of the COVID-19 pandemic on adolescents' mental health. We examined changes in depression and anxiety symptoms from before (2018-19) to the early (2019-20) and ongoing pandemic (2020-21) responses among Canadian adolescents in the context of a natural experiment. METHODS: We used linked survey data from 5,368 Canadian secondary school students who participated in three consecutive waves of the cannabis use, obesity, mental health, physical activity, alcohol use, smoking, and sedentary behaviour study during the 2018-19, 2019-20, and 2020-21 school year. Separate fixed effects models examined whether changes in depression (Center for Epidemiologic Studies Depression Scale Revised-10) and anxiety (General Anxiety Disorder-7) symptoms differed between two cohorts. The cohorts differed in the timing of their second data collection wave; one cohort participated before the pandemic and the other cohort participated in the early pandemic (spring 2020). RESULTS: Depression and anxiety symptoms increased during the early and ongoing pandemic periods in the overall sample and both cohorts. The two cohorts experienced similar elevations in their symptoms. Females and younger respondents presented greater elevations over time. The proportion of adolescents with significant depressive (29.4%) and moderate-to-severe anxiety (17.6%) symptoms at baseline increased by 1.5 times, reaching 44.8% and 29.8% in the ongoing pandemic period, respectively. DISCUSSION: Findings suggest that internalizing symptoms have consistently increased since before the onset of COVID-19, particularly in the ongoing pandemic period; however, we found no evidence of the increase being due to the pandemic in the early COVID-19 period when comparing the two cohorts. Ongoing evaluation of adolescents' mental health is necessary to capture potentially dynamic impacts over time.

The association between single and dual use of cannabis and alcohol and driving under the influence and riding with an impaired driver in a large sample of Canadian adolescents.

OBJECTIVE: Dual use of cannabis and alcohol has increased in adolescents, but limited research has examined how it relates to impaired driving or riding with an impaired driver (IDR) compared to single substance use. This study aimed to examine the odds of alcohol- and/or cannabis-IDR among adolescents based on their use of alcohol and/or cannabis, and whether associations differed by gender and age. METHODS: Cross-sectional survey data were used from a sample of 69,621 students attending 182 Canadian secondary schools in the 2021/22 school year. Multilevel logistic regression estimated the odds of exclusive alcohol-IDR, exclusive cannabis-IDR, and both alcohol and cannabis IDR (alcohol-cannabis-IDR). Substance use interactions with gender and age were tested. RESULTS: Overall, 14.7% of participants reported IDR; 7.5% reported exclusive alcohol-IDR, 3.2% reported exclusive cannabis-IDR, 4.0% reported alcohol-cannabis-IDR, and 7.4% were unsure if they had experienced IDR. The prevalence of IDR varied across substance use groups, 8.0% among nonuse, 21.9% among alcohol-only use, 35.9% among cannabis-only use, and 49.6% among dual use groups. Gender diverse, older, and students with lower socioeconomic status exhibited a higher likelihood of reporting alcohol-cannabis-IDR. Dual use was significantly associated with 9.5 times higher odds of alcohol-cannabis-IDR compared to alcohol-only use, and 3.0 times higher odds compared to cannabis-only use. Dual use was also associated with an increased likelihood of either alcohol- or cannabis-IDR. CONCLUSIONS: This study highlights that all students, regardless of substance use, are at risk of IDR, but students engaged in dual use of alcohol and cannabis face an elevated risk compared to both peers who do not use substances and those who use only a single substance. These findings emphasize the importance of targeted interventions that address the risks associated with IDR.

Evaluating the One-Year Impact of School e-Cigarette Use Interventions among Current Youth e-Cigarette Users in the COMPASS Study, 2017/18-2018/19.

There is a lack of evidence for the impact of school-based e-cigarette interventions among current e-cigarette users. This natural experimental evaluation study evaluated the one-year impact of various school-based e-cigarette prevention/cessation programs among a sample of current youth e-cigarette users. The COMPASS study sample included n = 3586 current e-cigarette users from n = 90 schools with data collected between 2017 and 2019. Student e-cigarette use patterns were categorized as "escalated", "maintained", and "reduced" based on the change in past 30-day e-cigarette use between baseline and follow-up. Intervention schools added e-cigarette use "prevention", "cessation", or "protection" programs, while control schools did not make any changes. Logistic regression models identified how each category of added programs was associated with e-cigarette use patterns. About one quarter of schools added an e-cigarette use prevention/cessation program over one year. Student e-cigarette use patterns between control and intervention groups differed in proportion ranging from a decrease of 3.35% to an increase of 5.80%. Regression models did not identify any significant differences in the odds of escalating or reducing e-cigarette use in intervention relative to control schools. While many schools implemented new e-cigarette programs over one year, none of the interventions led to significant changes in e-cigarette escalation or reduction among current youth e-cigarette users. Additional studies are needed to evaluate the impact of e-cigarette interventions among current e-cigarette users.

Dynamic Changes in Drinking Behaviour among Subpopulations of Youth during the COVID-19 Pandemic: A Prospective Cohort Study.

OBJECTIVE: Youth drinking is highly heterogenous, and subpopulations representing different alcohol use patterns may have responded differently to the COVID-19 pandemic. This study examined changing patterns of alcohol use in subpopulations of the youth population over the first two years of the pandemic. METHOD: We used linked survey data from 5367 Canadian secondary school students who participated in three consecutive waves of the COMPASS study between 2018/19 and 2020/21. Latent transition analysis (LTA) was used to identify patterns of alcohol use based on the frequency of drinking and frequency of binge drinking and to estimate the probability of transitioning between identified patterns. RESULTS: LTA identified five patterns of alcohol use each representing a unique subpopulation: abstainer, occasional drinker-no binging, occasional binge drinker, monthly binge drinker, weekly binge drinker. Probability of being engaged in binge drinking for a subpopulation of occasional drinkers pre-pandemic was 61%, which reduced to 43% during the early-pandemic period. A lower proportion of occasional binge drinkers reported moving to monthly or weekly binge drinking. Female occasional drinkers were more likely to move to binge drinking patterns during the pandemic than males. CONCLUSIONS: Less frequent drinking and younger students were more likely to reduce their drinking and binge drinking than more established drinkers during the COVID-19 pandemic. Understanding of heterogenous patterns of alcohol drinking and different responses to public health crises may inform future preventive programs tailored to target subpopulations more effectively.

Reciprocal associations between positive emotions and resilience predict flourishing among adolescents. / Les associations réciproques entre émotions positives et résilience prédisent l'épanouissement chez les adolescents.

INTRODUCTION: The broaden and build theory of positive emotions maintains that positive emotions serve to broaden individuals' thoughts and behaviours, resulting in the accrual of resources (e.g. resilience) that catalyze upward spirals of well-being. However, there is a relative dearth of research examining the upward spiral hypothesis in the context of adolescence. METHODS: Adolescents (n = 4064) in participating Canadian high schools were surveyed annually for three years as part of the COMPASS study. Reciprocal associations between positive emotions and resilience were examined as predictors of flourishing. RESULTS: Adolescents who experienced positive emotions more frequently than usual reported higher levels of resilience one year later. Similarly, adolescents who had higher levels of resilience than usual reported more positive emotions the following year. Higher than usual levels of resilience and positive emotions positively predicted flourishing. CONCLUSION: Positive emotions result in a cascade of beneficial outcomes including increased resilience and enhanced well-being, catalyzing an upward spiral towards flourishing. Opportunities to enhance positive emotions early on in adolescence may help build resources that can set students on the path towards increased well-being.

High-resolution examination of changes in drinking during the COVID-19 pandemic: Nine-wave findings from a longitudinal observational cohort study of community adults.

Few multi-wave longitudinal studies have examined changes in drinking across extended periods of the coronavirus 2019 (COVID-19) pandemic. Using multiple indicators over three years, the current study examined: a) overall drinking changes; b) sex, income, age, and pre-COVID drinking level as moderators of changes; and c) the clinical significance of the observed changes. Using a longitudinal observational cohort design with nonclinical adults from the general community (N = 1395), assessments were collected over nine waves, two pre-COVID (April 2019 and October 2019) and seven intra-COVID (April 2020-April 2022). Drinking was measured as percent drinking days, percent heavy drinking days, and the Alcohol Use Disorders Identification Test (AUDIT) score. Clinically significant changes were defined based on the World Health Organization risk levels. All indicators exhibited significant changes from pre-pandemic to intra-pandemic periods, with drinking changes comprising early pandemic increases followed by subsequent decreases and AUDIT scores consistently declining. Pre-pandemic drinking level substantially moderated all changes. Heavier drinkers exhibited larger decreases compared to other drinking groups. In terms of clinically important changes, ∼10% of pre-pandemic abstinent or low-risk drinkers transitioned to medium- or high-risk status during the pandemic. In contrast, 37.1% of medium-risk drinkers and 44.6% of high-risk drinkers exhibited clinically significant decreases during the intra-pandemic period. Collectively, these findings highlight the multifarious impacts of the pandemic on drinking over time, comprising both increases and decreases in drinking behaviour.

Periodicity and severity of changes in depression and anxiety during the COVID-19 pandemic: Ten-wave longitudinal findings from an observational cohort study of community adults.

AIMS: Few multi-wave longitudinal studies have examined mental health changes across the coronavirus 2019 (COVID-19) pandemic. The current study examined: (a) overall changes in depression and anxiety over 10-waves of data collection; (b) subgroup moderators of changes; (c) clinical severity of the changes via minimally important differences (MIDs); and (d) correlates of clinically important changes. METHODS: Using a longitudinal observational cohort design, 1412 non-clinical adults (Mage=36; 60% female) were assessed for depression and anxiety via the PHQ-9 and GAD-7 from October 2018 to April 2022 (3 pre-pandemic, 7 intra-pandemic waves; M retention = 92%). RESULTS: Depression and anxiety exhibited significant intra-pandemic changes, reflecting initial increases, followed by decreases. Pre-pandemic severity moderated changes, with low severity participants exhibiting increases and high severity participants exhibiting non-significant change or decreases. For depression and anxiety, respectively, 10% and 11% exhibited MID increases, while 4% and 6% exhibited MID decreases. Divergent patterns were present by severity subgroup, with the lowest severity exhibiting higher rates of MID increases and the highest severity subgroup exhibiting higher rates of MID decreases. CONCLUSIONS: These findings illuminate the periodicity of depression and anxiety during the COVID-19 pandemic and reveal an unexpected inverse relationship between increases and decreases based on pre-pandemic severity.

Changes in posttraumatic stress disorder symptom severity during the COVID-19 pandemic: Ten-wave findings from a longitudinal observational cohort study of community adults.

Few studies have examined changes in posttraumatic-stress disorder (PTSD) symptomatology across an extended time period during the COVID-19 pandemic. This study used a longitudinal cohort design to examine: (1) changes in overall PTSD symptoms and symptom clusters; (2) moderators of change; (3) the clinical significance of observed changes; and (4) correlates of clinically meaningful changes. Community adults (N = 1412) were assessed using the PTSD Checklist for DSM-5 (PCL-5) at 10 timepoints (October 2018 - April 2022). Changes in overall PCL-5 score and symptom clusters were substantially moderated by pre-pandemic clinical severity (i.e., above/below PCL-5 cut-off). Pre-pandemic non-clinical participants exhibited increases in overall scores, Cluster D (negative cognitions), and Cluster E (arousal), while clinically elevated participants exhibited decreases overall and in all clusters. Regarding clinical significance, 12% of pre-pandemic non-clinical participants exhibited clinically meaningful increases, and 4% exhibited decreases. Conversely, 42% of the pre-pandemic elevated group exhibited clinically meaningful decreases, while 6% exhibited increases. Pandemic impacts in numerous psychosocial domains were associated with clinically meaningful change. Collectively, these findings reveal substantively divergent trajectories by pre-pandemic severity and PTSD symptom cluster. The large proportion of pre-pandemic high-severity participants exhibiting sizable decreases was an unexpected notable observation.

Examining the Impact of the COVID-19 Pandemic on youth Alcohol Consumption: longitudinal Changes From Pre-to Intra-pandemic Drinking in the COMPASS Study.

PURPOSE: To date, there are few longitudinal studies on the COVID-19 pandemic's ongoing impact on youth drinking. This study examines the changes in drinking during two phases of the pandemic in a sample of Canadian youth. METHODS: We used four-year longitudinal data from the COMPASS study, including 14,085 secondary school students from Quebec and Ontario, Canada who provided linked data for any two consecutive years between 2017/18 and 2018/19 (pre-pandemic) waves, and 2019/20 and 2020/21 (during the initial and ongoing pandemic). A difference-in-difference (D-I-D) model was used to compare changes in the frequency of drinking and binge drinking between pre-COVID-19 to initial- and ongoing-pandemic period, while adjusted for age-related effects. RESULTS: The expected escalation in the frequency of drinking and binge drinking from the pre-pandemic wave (2018/19) to the initial pandemic (2019/20) was less than the changes seen across the 2017/18 to 2018/19 waves among sex and age groups. However, the second year of COVID was associated with an increase in the frequencies of both drinking and binge drinking. Male and younger students (aged 12-14) differentially increased their consumption. DISCUSSION: After a reduction in the initial pandemic period, the frequency of drinking and binge drinking rebounded in the second year, indicating that the pandemic's effects are not singular and have changed over time. Further examination is needed to understand the ongoing effects of the pandemic by continuing to monitor drinking in youth toward informing public health measures and harm reduction strategies.

Public health guideline compliance and perceived government effectiveness during the COVID-19 pandemic in Canada: Findings from a longitudinal cohort study.

BACKGROUND: The coronavirus disease 2019 (COVID-19) pandemic has imposed enormous adversity worldwide. Public health guidelines have been a first line of defense but rely on compliance with evolving recommendations and restrictions. This study sought to characterize adherence to and perceptions of public health guidelines over a one-year timeframe during the pandemic. METHODS: Participants were 1435 community adults in Ontario who completed assessments at five time points (April 2020, July 2020, October 2020, January 2021, and April 2021; 92% retention). Participants were assessed for self-reported adherence to government protocols and perceptions of government response (importance, compliance, and effectiveness). Analyses used general linear mixed-effects modelling of overall changes by time and examined differences based on age and sex. FINDINGS: Over time, participants reported high or increasing behavioural engagement in public health guidelines, including physical distancing, restricting activity, and masking. In contrast, participants exhibited significant reductions in perceived importance and compliance, with evidence of more negative changes in younger participants. The largest changes were a substantial reduction in perceived government effectiveness, from predominantly positive perceptions to predominantly negative perceptions. INTERPRETATION: These results illuminate evolving trends in public health compliance and perceptions over the course of the pandemic in Canada, revealing the malleability of public perceptions of public health recommendations and government effectiveness. FUNDING: This research was funded by a grant from the Canadian Institutes of Health Research (CIHR). CIHR had no role in study design, data collection, data analysis, interpretation, or writing of the report.

A longitudinal examination of alcohol cessation and academic outcomes among a sample of Canadian secondary school students.

INTRODUCTION: The negative effects of alcohol consumption on learning ability and intellectual development of youth may be recovered after cessation. This study explored to what extent reduction or complete cessation of alcohol consumption affects school performance of secondary school students. METHODS: Alcohol use was self-reported by 37,223 grade 9-12 students attending 89 secondary schools across Ontario (n = 79) and Alberta (n = 10), Canada, participating in the COMPASS study over four years (school years 2013-14 to 2016-17). Measures included past-year frequency of drinking and frequency of binge drinking. A first-order autoregressive multinomial logistic regression was used to establish the impact of reduction or cessation of alcohol use on school performance. RESULTS: During follow-up, 1465 (6.4%) reductions and 1903 (8.3%) cessations in alcohol consumption, and 1447 (10.1%) reductions and 2147 (14.9%) cessations of binge drinking were reported. Male students reported more cessation in both drinking (9.7% male vs 7.1% female) and binge drinking (15.6% male vs 14.4% female), though female students had higher rates of reductions. Students who quit or reduced their drinking or binge drinking were less likely to skip classes, leave their homework incomplete, or expect to get or to aspire to educational qualifications above a high school diploma compared to those who continued their alcohol use. CONCLUSIONS: Aside from health benefits, reduction or cessation of alcohol use may improve students' academic rigor. Prioritising school-based alcohol prevention efforts may therefore be beneficial for aspects of academic performance.

Changes in cannabis use modes among Canadian youth across recreational cannabis legalization: Data from the COMPASS prospective cohort study.

INTRODUCTION: Canadian youth consume cannabis in multiple ways, including by smoking, vaping, and eating or drinking. Existing evidence suggests that these behaviours may change after law liberalization, though data regarding youth are scarce. We investigated changes in cannabis modes of use and associated factors across the federal legalization of recreational cannabis use for adults in Canada, among a large sample of underage youth before alternative products were made legally available. METHODS: Data were available from 2953 longitudinally linked Canadian high school students who reported on their cannabis use during the 2017/2018 and 2018/2019 school years. We explored whether students maintained a single or multiple cannabis use mode(s), contracted, or expanded the number of modes used. We then used generalized estimating equations to analyse associations of baseline characteristics with use mode trajectory. RESULTS: Expansion of cannabis use modes (42.3%) was more common than maintenance of a single mode (31.3%), maintenance of multiple modes (14.3%), or reduction (12.1%). Students who maintained multiple modes were significantly more likely to have high amounts of weekly spending money (AOR 1.68), to binge drink (AOR 2.25) or vape (AOR 1.99), to use cannabis regularly (AOR 2.67), and to endorse more symptoms of depression (AOR 1.06). School support for quitting tobacco, drug, or alcohol use appeared to have no effect. CONCLUSIONS: Multi-modal cannabis use increased among Canadian youth in our sample. Its association with other substance use and depressive symptoms may indicate clustering of additional harms. Screening for this use pattern may assist in identifying high-risk substance use and should be considered in the design of harm reduction programming.