Drug use among adolescents is a significant global challenge [1,2], with increasing concern regarding the co-use of alcohol and cannabis [3]. The World Health Organization (WHO) identifies substance use during adolescence as a major public health issue, affecting millions worldwide [4]. This age group is particularly vulnerable to the effects of substance use, as their brains are still developing, and early use can lead to a variety of long-term health and social consequences [2-4]. The United Nations Office on Drugs and Crime, in their 2023 World Drug Report [5], highlighted the prevalence of substance use among adolescents. According to their findings, an estimated 5.6% of young people aged 15-16 worldwide have used cannabis in the past year [5]. This figure is indicative of the reach of cannabis among adolescents on a global scale. Furthermore, alcohol use in this age group is reported to be even higher than cannabis use, pointing to a more widespread issue with alcohol among young people [5]. These findings underscore the growing prevalence of substance use in this vulnerable age group, raising alarms about the potential long-term consequences on physical, mental, and social health. Substance use during adolescence can have far-reaching effects, impacting everything from academic performance and interpersonal relationships to an increased risk of developing substance use disorders later in life [6]. Additionally, tobacco and alcohol use are pervasive global issues among adolescents, often serving as gateways to other forms of substance abuse [7].

In the Philippines, a 2022 government survey highlighted a concerning trend in adolescent substance use, particularly regarding the age at which individuals first use drugs [8]. The study showed that 41.3% of first-time drug users were between the ages of 15 and 19. Usage patterns varied, with about 38.7% of respondents reporting drug use two to five times a week, 24.7% monthly, and 20.6% weekly [8]. Further insights into adolescent alcohol consumption are provided by the 2018 Expanded National Nutrition Survey, which documented fluctuations in the rates of current drinkers among adolescents [9]. The survey documented a decrease from 21.7% in 2008 to 18.6% in 2013, followed by an increase from 14.9% in 2015 to 16.8% in 2018. Among adolescents aged 10 to 19, 16.8% were identified as current drinkers, with 4.0% engaging in binge drinking. Additionally, a cross-sectional survey conducted as part of the Global School-based Student Health Survey, which involved 33 184 adolescents from Indonesia, Laos, the Philippines, Thailand, and Timor-Leste, revealed that 3.1% of school-aged adolescents reported using cannabis in the past month [10]. The prevalence ranged from 0.4% in Laos to 5.6% in the Philippines, highlighting regional variations in substance use trends among adolescents. Since 1972, cannabis has been illegal in the Philippines, with the laws becoming even more stringent in 2002 when the Comprehensive Dangerous Drugs Act designated cannabis as a “dangerous drug” [11]. The severity of the Philippines’ cannabis laws, which impose some of the harshest penalties worldwide for possession, use, and distribution, casts adolescent cannabis use in a particularly complex light.

Despite the alarming statistics presented, the literature reveals significant gaps in our understanding of substance use among Filipino adolescents, particularly regarding the co-use of alcohol and cannabis [9,10]. Current research often overlooks the specific patterns of alcohol and cannabis co-use, the socioeconomic and cultural dynamics involved, and the particular factors contributing to these behaviors within the Filipino context. Most existing studies focus on single substance use, provide outdated data, or are geographically limited [8-10], leaving a critical gap in comprehensive, recent, and culturally sensitive research. This gap in the literature underscores the urgent need for updated and localized research that can inform targeted interventions and policies.

The primary aim of this study is to bridge the above-discussed knowledge gaps by investigating the predictors and prevalence of alcohol and cannabis co-use among 9263 adolescents in the Philippines, utilizing data from a school-based student health survey. This research strives to offer a detailed empirical analysis of the extent and nature of co-use, and to identify the key factors associated with these behaviors.

In this study, which included 9263 participants, 360 participants (weighted prevalence, 4.2%; 95% CI, 3.4 to 5.3) were identified as co-users of both alcohol and cannabis. Additionally, 1726 participants (weighted prevalence, 19.2%; 95% CI, 17.8 to 20.7) reported exclusively using alcohol, without concurrent cannabis use. Conversely, 290 participants (weighted prevalence, 3.2%; 95% CI, 2.7 to 3.7) reported exclusive use of cannabis, without alcohol consumption. Furthermore, a significant proportion of our study cohort, comprising 6887 participants (weighted prevalence, 73.4%; 95% CI, 71.4 to 75.4), did not use either alcohol or cannabis.

Table 1 presents the demographic characteristics of the study participants. Significant age-related differences were observed between the two groups. The co-user group included a higher proportion of individuals aged less than 15 years (71.9 vs. 64.8% in non-co-users), and a smaller proportion aged 15 years and older (28.1 vs. 35.2%), with a statistically significant p-value of 0.006. Sex disparities were also notable. Among co-users, a majority were male (76.8%), significantly higher than in the non-co-user group (43.4%). In contrast, females constituted 23.2% of the co-user group and 56.6% of the non-co-users; this difference was statistically significant (p<0.001). The distribution of academic years also varied markedly between groups, with a higher percentage of co-users in grade 7 (40.0 vs. 24.9%) and grade 8 (31.6 vs. 24.9%), and lower percentages in higher academic years. This trend was statistically significant (p<0.001).

A higher proportion of co-users reported always feeling lonely (28.7 vs. 24.0% among non-co-users) and experiencing poor sleep quality (30.2 vs. 15.5%), with both differences being statistically significant (p-values of 0.045 and <0.001, respectively). The incidence of attempted suicide was alarmingly higher among co-users (59.7%) compared to non-co-users (21.2%) (p<0.001). Similarly, a smaller proportion of co-users reported having no close friends (13.6 vs. 5.3% among nonco-users), a difference that was also statistically significant (p<0.001). Physical activity patterns differed significantly; a smaller percentage of co-users were not physically active (20.2 vs. 41.3% among non-co-users) (p<0.001). Bullying experiences also varied; co-users experienced more bullying outside of school (45.9 vs. 31.1%), although no significant difference was observed in school bullying. Additionally, a smaller percentage of co-users reported not attending physical education classes (20.0 vs. 14.8% among non-co-users, p=0.008) and a lower percentage reported that their parents or guardians understood their worries (24.9 vs. 31.5%, p=0.009).

Parental supervision showed significant differences; co-users experienced less frequent unapproved parental checks (54.5 vs. 67.1%) and a smaller percentage reported that their parents were aware of their free time activities (25.9 vs. 33.6%). Both of these differences were statistically significant (p-values <0.001 and 0.003, respectively).

Table 2 shows the results of multivariable logistic regression analysis aimed at identifying the predictors of alcohol and cannabis co-use among adolescents. The analysis was adjusted for several variables, including demographic factors, educational background, psychological aspects, and behavioral tendencies. Age group did not emerge as a significant determinant in this analysis (p=0.069), with participants aged 15 years and greater having an aOR of 1.42 (95% CI, 0.97 to 2.10) compared to those less than 15 years. However, sex was a significant predictor (p<0.001), with males exhibiting significantly higher odds of co-use (aOR, 4.50; 95% CI, 3.31 to 6.10) than females. In terms of academic year, grade 7 students had significantly higher odds of co-use compared to grade 10 (aOR, 4.08; 95% CI, 2.39 to 6.99; p<0.001). Similarly, grade 8 students showed higher odds of co-use (aOR, 2.20; 95% CI, 1.30 to 3.72; p=0.003), while grade 9 students did not show a statistically significant difference from grade 10 students in this regard.

Psychological and behavioral factors also played a role. Always feeling lonely did not show a significant association with co-use (p=0.237). Poor sleep quality was a significant predictor (aOR, 1.77; 95% CI, 1.29 to 2.44; p<0.001), as was a history of attempted suicide (aOR, 5.31; 95% CI, 4.00 to 7.06; p<0.001). Having no close friends, however, was not a significant factor. Physical inactivity was associated with lower odds of co-use (aOR, 0.45; 95% CI, 0.33 to 0.62; p<0.001). Participants who did not attend physical education classes had higher odds of co-use (aOR, 1.48; 95% CI, 1.06 to 2.05; p=0.021). Other factors, such as being bullied outside school and whether a parent/guardian understood their worries, were not significant predictors. Parental monitoring was found to have a significant relationship, with infrequent unapproved parental checks associated with higher odds of co-use (aOR, 1.37; 95% CI, 1.04 to 1.80; p=0.024). Conversely, participants whose parents were less aware of their free-time activities had lower odds of co-use (aOR, 0.63; 95% CI, 0.45 to 0.87; p=0.005).

To the best of our knowledge, our study is the first to examine the prevalence and predictors of alcohol and cannabis couse among Filipino adolescents. We found that the weighted prevalence of alcohol and cannabis co-use in this group is 4.2%. This result is consistent with studies from outside the Philippines [15-17], which have reported that substance couse among adolescents is relatively common, indicating a global trend of substance experimentation during adolescence. Our findings also reveal demographic disparities, particularly a higher prevalence of substance co-use among males and younger age groups, aligning with prior research [18,19]. Similar patterns have been observed in studies from European and Asian countries, where males are more likely to engage in substance use [20-23]. This trend may be related to sex differences in risk-taking behaviors and social norms. Additionally, the higher prevalence of substance use among younger age groups is concerning, as it suggests potential long-term negative impacts on adolescent development and health due to early exposure to substances.

The significant association between poor sleep quality and substance co-use among Filipino adolescents underscores a critical aspect of adolescent health that demands focused attention. Poor sleep quality can intensify stress and emotional instability, increasing the likelihood that adolescents will turn to substance use. This observation is consistent with international studies that describe a cyclical relationship between sleep disturbances and substance use, where each condition may exacerbate or trigger the other [24]. In the Philippines, this indicates a need for interventions that address not only substance use but also underlying factors such as sleep hygiene. Schools and community health programs would benefit from including sleep education workshops that inform adolescents about the importance of sleep, its effects on overall health, and effective strategies for improving sleep habits. Additionally, healthcare providers should be encouraged to screen for sleep issues during routine assessments of adolescents.

The relationship between a history of attempted suicide and substance co-use highlights a critical intersection between mental health issues and risk behaviors in adolescents [25]. Unlike the general correlation with psychological distress, attempting suicide signifies a profound personal crisis and suggests that substance use among these adolescents may serve not only as a coping mechanism but also as a desperate escape from their psychological pain [25,26]. This distinction is crucial for tailoring prevention and intervention programs, emphasizing the need for acute mental health services that are accessible and equipped to support adolescents in crisis. It advocates for a dual approach where schools focus not only on substance abuse education but also on establishing robust support systems that include counseling services, suicide prevention programs, and crisis intervention teams. Integrating these services can provide a safety net for at-risk adolescents, potentially reducing the incidence of both substance use and suicide attempts. Establishing partnerships between educational institutions, mental health organizations, and community resources can facilitate a comprehensive network of support tailored to the needs of Filipino youth.

The lack of a significant association between loneliness and substance co-use in our study marks a notable departure from findings reported in other regions [27,28]. This difference may be attributed to cultural variations in social relationships and coping strategies among Filipino adolescents. In cultures where community and familial bonds are especially strong, the effects of loneliness on behaviors such as substance use may be lessened by these supportive networks. This observation suggests that interventions in the Philippines could be more effective if they capitalize on these existing social structures, promoting family and community involvement as protective factors against substance use. Additionally, this finding encourages a more detailed examination of the social dynamics of Filipino adolescents, urging future research to investigate how cultural contexts influence the relationship between loneliness and risk behaviors.

Our findings on the inverse relationship between physical activity and substance co-use among adolescents align with global studies that suggest active participation in physical activities serves as a protective factor against substance use [29,30]. This relationship highlights the extensive benefits of physical activity, which go beyond physical health to encompass mental health and social well-being [31]. The positive effects of physical activity on mental health, possibly through the release of stress-relieving endorphins and the creation of a supportive social environment, provide a viable strategy for preventing substance use. Additionally, the link between skipping physical education classes and an increased likelihood of substance co-use underscores the importance of school-based physical activity programs. These programs should not only focus on boosting physical activity levels among students but also incorporate substance use education and foster social interactions as preventive measures against substance use.

Finally, the significant role of parental monitoring identified in this study is consistent with international research that underscores the protective effects of parental supervision in preventing adolescent substance use [32-34]. The association between less frequent unapproved parental checks, reduced parental awareness of adolescents’ free-time activities, and higher odds of co-use underscores the importance of parental involvement in adolescents’ lives. This aligns with findings from various cultural contexts that support active parental engagement and communication as effective strategies to prevent adolescent substance use [35,36]. However, these findings also prompt further discussion on finding the appropriate balance between supervision and autonomy in adolescent development, particularly in the Filipino context.

In direct response to the identified gaps and our study’s findings, we propose actionable recommendations for developing context-specific intervention and education programs aimed at mitigating the risks associated with the co-use of alcohol and cannabis among adolescents. Specifically, we advocate for the integration of specialized curriculum modules within schools that focus on the risks of substance co-use, emphasizing the unique challenges and health implications it presents. These modules should employ interactive and engaging methods, such as role-playing and peer-led discussions, to foster a deeper understanding and resilience against substance use. Additionally, policy recommendations include the implementation of community-based outreach programs that involve parents and guardians in substance use education, equipping them with the tools to effectively communicate and monitor their children’s activities. Furthermore, establishing mental health support services within educational institutions could provide a dual approach, addressing both the prevention of substance co-use and offering interventions for those at risk or already engaged in such behaviors. These recommendations are envisioned to function collaboratively across educational, familial, and community settings, ensuring a comprehensive approach to substance use prevention among Filipino adolescents. Implementing these strategies requires collaboration among policymakers, educators, and health professionals, on the basis of our findings, to create safer environments conducive to the well-being and healthy development of young people.

In light of the findings of this study, several recommendations for public health policy and practice are proposed. First, it is crucial to implement early intervention and prevention strategies in schools, with a particular focus on younger adolescents at the beginning of secondary education. These programs should include components that address mental health, physical activity, and substance use education, tailored to meet the developmental needs of this age group. Additionally, public health policies should promote parental involvement and educate parents about the importance of monitoring and communicating with their adolescent children about the risks of substance use. In terms of practice, healthcare providers should be trained to screen for substance use and related risk factors, such as poor mental health and low levels of physical activity, during routine adolescent health visits. For future research, there is a need to explore the underlying reasons for early initiation of substance co-use and the sex disparities observed in substance use patterns. Studies investigating the effectiveness of school-based interventions and parental involvement programs in the Filipino context would provide valuable insights for evidence-based policy-making. Furthermore, longitudinal studies are warranted to understand the long-term impacts of early substance co-use on physical, mental, and social health outcomes. This comprehensive approach, encompassing policy, practice, and research, is crucial in mitigating the risks associated with alcohol and cannabis co-use among adolescents in the Philippines and potentially in other similar contexts globally.

The study has several notable strengths, primarily due to its utilization of the GSHS. This tool, collaboratively designed by the WHO and the U.S. CDC, is both robust and globally recognized. It facilitates the collection of comprehensive and comparable data on adolescent health behaviors, thereby lending substantial credibility and reliability to the study’s findings. The large sample size of 9263 participants, coupled with a high response rate of 85%, significantly enhances the representativeness and generalizability of the results to the broader adolescent population in the Philippines. Furthermore, the study’s methodology, which included a thorough analysis of a wide range of variables such as demographic factors, mental health, physical activity, and familial influences, provides an understanding of the predictors of alcohol and cannabis couse among adolescents. This comprehensive approach lays a robust foundation for the study’s conclusions and recommendations, making it a valuable contribution to the field of adolescent substance use research.

However, the study is not without its limitations. As a cross-sectional analysis, it can identify associations but cannot establish causal relationships between variables, which leaves ambiguity regarding the directionality of these relationships. Additionally, the reliance on self-reported data may introduce bias, as participants might underreport or overreport their substance use due to social desirability or recall issues. The exclusion of adolescents not attending school also means that the findings may not be fully representative of all Filipino youth, particularly those who are out of school and may have different patterns of substance use. Furthermore, the study’s focus on alcohol and cannabis co-use might overlook the use of other substances, such as tobacco, which could also be relevant in this context. Lastly, the cultural and social nuances specific to the Philippines might limit the applicability of the findings to other cultural contexts, necessitating caution in generalizing the results globally. Despite these limitations, the study provides crucial insights into the patterns and predictors of substance co-use among adolescents in the Philippines, offering a solid base for future research and public health interventions.

In this study, which included 9263 Filipino adolescents, we explored the patterns and determinants of alcohol and cannabis co-use, finding a prevalence rate of 4.2%. Our findings indicate that the primary predictors of such co-use include male sex, enrollment in lower academic years, poor sleep quality, a history of attempted suicide, a lack of physical activity, nonparticipation in physical education classes, infrequent unapproved parental checks, and low parental awareness of their children’s activities during free time. Highlighting these insights, the study underscores the urgent need for tailored prevention strategies. These strategies should focus on early intervention, enhanced mental health support, and increased parental involvement, all aimed at mitigating the risks of substance use among adolescents.