The Short-Term Change in Knowledge of Cannabis-Related Risks After a Brief Curriculum-Integrated School Intervention Among Adolescents: A Quasi-Experimental Pre–Post Study

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

I would like to congratulate the authors on this important study. However, the presentation of the educational intervention, which constitutes the main hypothesis of the study, is quite weak. The results section appears to focus mainly on prevalence. Tables and analyses demonstrating the effectiveness of the education in the whole group and in subgroups are needed. For example, what were the pre- and post-education scores among those who use cannabis and other substances, and among those with a family history of substance use? What was the effect of the education on these outcomes? These analyses should be added. In addition, what is the relationship (interaction) between the increase or decrease in scores and family history of substance use? Furthermore, presenting the pre- and post-education scores with graphs would also improve the clarity and readability of the manuscript.

     

Comments on the Quality of English Language

I would like to congratulate the authors on this important study. However, the presentation of the educational intervention, which constitutes the main hypothesis of the study, is quite weak. The results section appears to focus mainly on prevalence. Tables and analyses demonstrating the effectiveness of the education in the whole group and in subgroups are needed. For example, what were the pre- and post-education scores among those who use cannabis and other substances, and among those with a family history of substance use? What was the effect of the education on these outcomes? These analyses should be added. In addition, what is the relationship (interaction) between the increase or decrease in scores and family history of substance use? Furthermore, presenting the pre- and post-education scores with graphs would also improve the clarity and readability of the manuscript.

     

Author Response

Reviewer 1

I would like to congratulate the authors on this important study.

Comment 1: However, the presentation of the educational intervention, which constitutes the main hypothesis of the study, is quite weak.

Response 1: We thank the reviewer for this important observation and agree that the original description of the intervention was too brief. In response, we strengthened the presentation of the educational intervention in the Methods section. The revised manuscript now provides a clearer description of the intervention structure, content, delivery format, duration, facilitators, and standardization procedures. Specifically, we clarified that the program consisted of three standardized 1-hour classroom sessions delivered by mental health specialist nurses during regular class time, focused on health literacy, correction of misconceptions, risk perception, peer influence, and resistance skills. We also clarified that delivery was standardized through a common script and uniform materials to improve transparency and support replicability.

Comment 2: The results section appears to focus mainly on prevalence. Tables and analyses demonstrating the effectiveness of the education in the whole group and in subgroups are needed. For example, what were the pre- and post-education scores among those who use cannabis and other substances, and among those with a family history of substance use? What was the effect of the education on these outcomes? These analyses should be added.

Response 2: We appreciate this helpful suggestion and agree that the original Results section placed too much emphasis on descriptive prevalence estimates. In response, we restructured the Results section to give greater prominence to the primary outcome, namely pre–post change in cannabis-risk knowledge. We now present the overall pre- and post-intervention knowledge scores in the full sample, including the median paired change, the proportion of students who improved, the Hodges–Lehmann estimate with 95% confidence interval, and the Wilcoxon effect size. In addition, we added a new table with exploratory subgroup analyses showing pre- and post-intervention medians, median change, proportion improved, within-group p-values, and effect sizes for students according to cannabis use status and according to any reported parental alcohol/cannabis use. Additional subgroup analyses for alcohol use, amphetamine use, cocaine use, and gambling were added in the supplementary tables. To better align the manuscript with the study design, we describe these findings as short-term within-subject change under uncontrolled conditions rather than as evidence of intervention effectiveness. We also moved the prevalence figure to the supplementary material so that the main manuscript focuses more clearly on the primary outcome.

Comment 3: In addition, what is the relationship (interaction) between the increase or decrease in scores and family history of substance use? Furthermore, presenting the pre- and post-education scores with graphs would also improve the clarity and readability of the manuscript

Response 3: We thank the reviewer for this valuable suggestion. In response, we conducted an additional exploratory analysis comparing change scores (post-test minus pretest knowledge score) according to whether students reported any parental alcohol/cannabis use. Because the study used a single-group pre–post design and was not powered for formal interaction modelling, we examined whether the magnitude of change differed between these groups using a Mann–Whitney U test. The median change was +5 points in both groups, and no significant difference in change scores was observed. To improve precision and avoid overstating this variable, we replaced the term “family history of substance use” with “any reported parental alcohol/cannabis use” throughout the manuscript, as this variable was derived from adolescent-reported parental use. In addition, as suggested, we added graphs showing the overall pre- and post-intervention knowledge scores and the distribution of change scores according to cannabis use status and according to any reported parental alcohol/cannabis use. These figures were incorporated into the main manuscript to improve clarity and readability.

Reviewer 2 Report

Comments and Suggestions for Authors

Reviewer Report

General assessment
The manuscript addresses a relevant public health topic and provides a pragmatic evaluation of a brief school-based cannabis education intervention. The paper is clearly written and well structured. However, important methodological limitations substantially constrain the interpretation of the findings. In its current form, the study provides evidence of short-term knowledge change but does not support conclusions about intervention effectiveness or broader practical impact.

Major comments

1. Study design
   The single-group pre–post design without a control group is a major limitation. The observed improvement in knowledge cannot be confidently attributed to the intervention, as alternative explanations such as testing effects, short-term memory, or maturation cannot be ruled out. The manuscript should further reduce any causal or effectiveness-oriented interpretations and clearly frame the results as within-subject change under uncontrolled conditions.
2. Outcome measure
   The primary outcome is based on an ad hoc knowledge scale without reported psychometric properties. There is no information on reliability or validity, and the close alignment between intervention content and measurement raises concerns about teaching-to-test effects and inflated effect sizes. This limitation should be more explicitly addressed.
3. Short follow-up
   The post-test was conducted two weeks after the intervention, which likely captures short-term recall rather than sustained knowledge or meaningful learning. The manuscript should more clearly frame the findings as short-term cognitive outcomes and avoid any implications related to prevention impact.
4. Interpretation of findings
   Although the authors acknowledge limitations, the discussion occasionally overextends toward practical implications such as scalability or policy relevance. These claims should be more carefully qualified and clearly separated from evidence of effectiveness.
5. Sampling issues
   The absence of information on the total eligible population and participation rate raises concerns about potential selection bias and limits generalizability. This should be more explicitly discussed.
6. Exploratory analyses
   Subgroup analyses are based on very small sample sizes and should be interpreted with greater caution. These findings should be clearly presented as hypothesis-generating and their prominence in the discussion reduced.
7. Implementation data
   No information is provided on intervention fidelity, adherence, or participant engagement. This limits interpretation of feasibility and scalability claims and should be acknowledged more explicitly.

Minor comments

The statistical reporting could be improved by including confidence intervals. The discussion contains some repetition and could be streamlined. The manuscript would benefit from a slightly stronger theoretical framing.

Overall, the manuscript has value as a pragmatic feasibility-oriented study, but substantial revision is required to align conclusions with the limitations of the design and measurement.

Author Response

Reviewer 2

General assessment

Comments 1: The manuscript addresses a relevant public health topic and provides a pragmatic evaluation of a brief school-based cannabis education intervention. The paper is clearly written and well structured. However, important methodological limitations substantially constrain the interpretation of the findings. In its current form, the study provides evidence of short-term knowledge change but does not support conclusions about intervention effectiveness or broader practical impact.

Response 1: We thank the reviewer for this thoughtful and constructive overall assessment. We agree that the manuscript’s main value lies in providing a pragmatic evaluation of short-term change in a proximal cognitive outcome under routine school conditions, and that important methodological limitations constrain interpretation. In response, we revised the manuscript throughout to more clearly position the study as a single-group, uncontrolled pre–post evaluation of within-subject short-term change in knowledge, rather than as evidence of intervention effectiveness, broader practical impact, or prevention impact. We also further qualified the interpretation of the findings in the Highlights, Abstract, Discussion, and Conclusions.

Major comments

Study design

Comments 2: The single-group pre–post design without a control group is a major limitation. The observed improvement in knowledge cannot be confidently attributed to the intervention, as alternative explanations such as testing effects, short-term memory, or maturation cannot be ruled out. The manuscript should further reduce any causal or effectiveness-oriented interpretations and clearly frame the results as within-subject change under uncontrolled conditions.

Response 2: We agree. Because the study used a single-group pre–post design without a control group, the observed improvement cannot be attributed exclusively to the intervention, and alternative explanations such as testing effects, item familiarization, short-term recall, maturation, or other uncontrolled influences cannot be ruled out. We therefore revised the manuscript to consistently describe the findings as short-term within-subject change under uncontrolled conditions, and we removed or softened wording that could imply causal effectiveness, comparative benefit, or prevention impact.

Outcome measure

Comments 3: The primary outcome is based on an ad hoc knowledge scale without reported psychometric properties. There is no information on reliability or validity, and the close alignment between intervention content and measurement raises concerns about teaching-to-test effects and inflated effect sizes. This limitation should be more explicitly addressed.

Response 3: We agree that the ad hoc knowledge scale is an important limitation. The instrument was developed specifically to reflect the intervention’s core content and to be sensitive to short-term change, but we did not assess or report psychometric properties. In response, we strengthened the description of the measure and the limitations section to explicitly acknowledge the absence of reliability and validity evidence, the limited comparability of the measure across studies, and the possibility of content alignment or teaching-to-test effects that may have inflated the observed magnitude of change.

Short follow-up

Comments 4: The post-test was conducted two weeks after the intervention, which likely captures short-term recall rather than sustained knowledge or meaningful learning. The manuscript should more clearly frame the findings as short-term cognitive outcomes and avoid any implications related to prevention impact.

Response 4: We agree. Because the post-test was conducted two weeks after the final session, the study captures a short-term cognitive outcome and does not allow conclusions about sustained knowledge retention, prevention impact, behavioural relevance, or longer-term learning. We revised the Abstract, Discussion, and Conclusions to more explicitly frame the findings as short-term change only and to avoid implying durable learning or prevention effects.

Interpretation of findings

Comments 5: Although the authors acknowledge limitations, the discussion occasionally overextends toward practical implications such as scalability or policy relevance. These claims should be more carefully qualified and clearly separated from evidence of effectiveness.

Response 5: We appreciate this point and agree that some practical implications were phrased too strongly. In response, we revised the manuscript to more clearly separate what is directly supported by the data from broader contextual reflections. Specifically, we reduced or removed language related to scalability, feasibility, and broader practical or policy relevance where it was not directly supported by the design, and we retained only a cautious statement that the findings may help inform future controlled and implementation-focused studies.

Sampling issues

Comments 6: The absence of information on the total eligible population and participation rate raises concerns about potential selection bias and limits generalizability. This should be more explicitly discussed.

Response 6: We agree. We now state more explicitly that the absence of information on the total eligible population and reasons for non-participation prevents calculation of the participation rate, raises the possibility of selection bias, and limits assessment of representativeness and generalizability beyond the participating classes and schools.

Exploratory analyses

Comments 7: Subgroup analyses are based on very small sample sizes and should be interpreted with greater caution. These findings should be clearly presented as hypothesis-generating and their prominence in the discussion reduced.

Response 7: We agree. These subgroup analyses were based on very small frequencies and were not intended for inferential interpretation. We therefore further de-emphasized these findings in the Discussion, presented them strictly as exploratory and hypothesis-generating, and clarified that the study was not designed or powered to examine subgroup differences or contextual associations.

Implementation data

Comments 8: No information is provided on intervention fidelity, adherence, or participant engagement. This limits interpretation of feasibility and scalability claims and should be acknowledged more explicitly.

Response 8: We agree. Although the intervention was standardized through a common script and uniform materials, we did not collect formal session-level data on fidelity, adherence to the script, quality of delivery, or participant engagement in this evaluation. Attendance alone is insufficient to characterize implementation. We therefore strengthened the limitations section to explicitly acknowledge that the consistency of delivery across classes and schools cannot be verified from the available data, and that feasibility, reproducibility, or scalability should not be inferred from the present findings alone.

Minor comments

Comments 9: The statistical reporting could be improved by including confidence intervals. The discussion contains some repetition and could be streamlined. The manuscript would benefit from a slightly stronger theoretical framing.

Overall, the manuscript has value as a pragmatic feasibility-oriented study, but substantial revision is required to align conclusions with the limitations of the design and measurement.

Response 9: We thank the reviewer for these helpful suggestions. In response, we revised the Discussion to reduce repetition and improve focus. We also strengthened the theoretical framing by more clearly situating cannabis-related knowledge and perceived risk as proximal cognitive mediators rather than distal behavioural outcomes. Regarding statistical reporting, we agree that confidence intervals improve precision and interpretability, and we have added them where feasible, including for the Hodges–Lehmann estimate of the paired change in the primary outcome. More comprehensive precision reporting should be incorporated in future controlled studies using psychometrically stronger outcome measures. We also revised the Conclusions to better align the interpretation of the findings with the limitations of the design and measurement.

Reviewer 3 Report

Comments and Suggestions for Authors

Dear Authors,

 

General Comment

This is an interesting piece of work; however, I consider that the secondary objectives are addressed only within the Results section and do not appear to form part of the central focus of the study.

 

Highlights

The highlights are consistent with the work that the authors intend to develop.

 

Introduction

I consider it important to include information on the magnitude of marijuana use among school-aged adolescents in Spain, in order to emphasize that this represents a public health issue.

In the first paragraph, the introduction begins by stating that marijuana is the most widely used drug worldwide, and the paragraph concludes by noting that this is also the case in Spain. I would recommend reorganizing this section to avoid repetition of information.

It would also be valuable to strengthen the discussion regarding the limited available evidence on school-based interventions.

Towards the end of the Introduction, secondary objectives are presented; however, the section itself is primarily framed around interventions. These secondary objectives appear somewhat forced within the structure of the manuscript. I recommend reconsidering whether they are necessary for the development of the study and whether they genuinely contribute to the overall objective.

 

Methods

The study design is described; however, in addition to the use of the TIDieR checklist, I recommend considering the guidance provided by ROBINS-I (Risk Of Bias In Non-randomized Studies of Interventions) for non-randomized intervention studies.

In the description of the study population, it is important to specify participants’ ages. For readers unfamiliar with the Spanish educational system, it may not be clear which stage of adolescence the participants represent.

Further details regarding the intervention is required to ensure replicability. Likewise, additional information about the professional profiles of those delivering the intervention should be provided.

It is necessary to describe the scale used to assess knowledge, including its psychometric properties.

I consider that assessing the consumption of other substances constitutes a separate objective that does not clearly contribute to the conclusions regarding the intervention. Nevertheless, if the authors deem this necessary to strengthen the manuscript, it would be important to clearly define the criteria used to classify participants as daily users, non-daily users, or non-users, ensuring that these categories align with established consumption criteria.

 

Results

The Results section appears to focus mainly on the secondary objectives, while only one paragraph presents findings related to the primary objective. If the authors consider this section too brief, additional analyses — for example, stratification by sex or other relevant variables — could strengthen the evaluation of the intervention’s main objective.

 

Discussion

The discussion appropriately addresses the principal objective; however, the secondary objectives are not discussed. Therefore, I recommend reconsidering their inclusion or removing them from the manuscript.

 

Conclusions

The conclusions are consistent with the primary objective of the study.

 

Author Response

Reviewer 3

We thank the reviewer for the careful reading of the manuscript and for these thoughtful suggestions, which helped us improve the focus, clarity, and methodological transparency of the paper.

Comment 1: General Comment

This is an interesting piece of work; however, I consider that the secondary objectives are addressed only within the Results section and do not appear to form part of the central focus of the study.

Response 1: We thank the reviewer for this important observation and agree that the central focus of the manuscript should be the primary objective, namely short-term pre–post change in cannabis-risk knowledge after the school-based intervention. In response, we revised the manuscript to further emphasize the primary outcome throughout the Results, Discussion, and Conclusions. We also reduced the prominence of the secondary objectives and clarified that they are included only to contextualize the sample and to explore selected associations on a strictly exploratory, non-inferential basis. To better reflect this hierarchy, the main manuscript now gives greater visual and analytical prominence to the primary outcome, while prevalence and related contextual analyses were de-emphasized and partly moved to the supplementary material. These revisions were also made in line with Reviewer 1’s request to prioritize analyses of the intervention outcome and Reviewer 2’s request to reduce overinterpretation of exploratory findings.

Comment 2: Highlights

The highlights are consistent with the work that the authors intend to develop.

Response 2: We thank the reviewer for this positive assessment.

Comment 3: Introduction

I consider it important to include information on the magnitude of marijuana use among school-aged adolescents in Spain, in order to emphasize that this represents a public health issue.

Response 3: We agree. In response, we strengthened the Introduction by more clearly describing the magnitude of cannabis use among adolescents in Spain and by explicitly framing this as a relevant public health issue in the national context.

Comment 4: In the first paragraph, the introduction begins by stating that marijuana is the most widely used drug worldwide, and the paragraph concludes by noting that this is also the case in Spain. I would recommend reorganizing this section to avoid repetition of information.

Response 4: We agree and revised the opening paragraph to improve flow and reduce repetition. The Introduction now presents the broader context first and then narrows more clearly to the Spanish adolescent context, avoiding redundant restatement of the same idea.

Comment 5: It would also be valuable to strengthen the discussion regarding the limited available evidence on school-based interventions.

Response 5: We agree. We revised the Introduction to more clearly situate the study within the limited evidence base for brief, curriculum-integrated school interventions delivered under routine conditions. We also added discussion of the gap between evidence from more intensive or controlled programs and the need for pragmatic evaluations under usual school conditions.

Comment 6: Towards the end of the Introduction, secondary objectives are presented; however, the section itself is primarily framed around interventions. These secondary objectives appear somewhat forced within the structure of the manuscript. I recommend reconsidering whether they are necessary for the development of the study and whether they genuinely contribute to the overall objective.

Response 6: We appreciate this comment and agree that the manuscript should remain primarily centered on the intervention and its main outcome. We therefore revised the framing of the secondary objectives to make clear that they are contextual and exploratory only. We retained them because they help characterize the participating sample and provide limited contextual information relevant to interpretation of the findings, but we reduced their prominence and explicitly stated that they were not intended to contribute inferentially to conclusions about the intervention.

Comment 7: Methods

The study design is described; however, in addition to the use of the TIDieR checklist, I recommend considering the guidance provided by ROBINS-I (Risk Of Bias In Non-randomized Studies of Interventions) for non-randomized intervention studies.

Response 7: We thank the reviewer for this helpful suggestion. We agree that risk of bias is an important consideration in non-randomized studies. Although we did not formally apply the ROBINS-I tool in this manuscript, we revised the paper to more explicitly address the main sources of bias and threats to internal validity inherent to the single-group pre–post design, including testing effects, item familiarization, short-term recall, maturation, and other uncontrolled influences. We also further qualified the interpretation of the findings throughout the manuscript to avoid causal or effectiveness-oriented wording.

Comment 8: In the description of the study population, it is important to specify participants’ ages. For readers unfamiliar with the Spanish educational system, it may not be clear which stage of adolescence the participants represent.

Response 8: We agree. We clarified the age range of the participants in the Abstract and Results, indicating that the sample included adolescents aged 15–17 years, and we retained the description of their school level to improve interpretability for international readers.

Comment 9: Further details regarding the intervention is required to ensure replicability. Likewise, additional information about the professional profiles of those delivering the intervention should be provided.

Response 9: We agree and expanded the description of the intervention in the manuscript. The revised version now clarifies that the program consisted of three standardized 1-hour classroom sessions delivered over three consecutive weeks, focused on health literacy, correction of misconceptions, risk perception, peer influence, and resistance skills. We also specify that the sessions were delivered by mental health specialist nurses and that content and delivery were standardized through a common script and uniform materials. These changes were introduced to improve transparency and to provide sufficient detail for replication.

Comment 10: It is necessary to describe the scale used to assess knowledge, including its psychometric properties.

Response 10: We agree that this issue required clearer treatment. In response, we strengthened the Methods and Discussion sections to describe the knowledge scale in greater detail, including its scoring, content focus, and intended use as a short-term, intervention-specific measure. We also explicitly acknowledged that no formal psychometric evaluation was conducted prior to this study and discussed the implications of this limitation, including the absence of reliability and validity evidence, limited comparability across studies, and the possibility of content-alignment or teaching-to-test effects.

Comment 11: I consider that assessing the consumption of other substances constitutes a separate objective that does not clearly contribute to the conclusions regarding the intervention. Nevertheless, if the authors deem this necessary to strengthen the manuscript, it would be important to clearly define the criteria used to classify participants as daily users, non-daily users, or non-users, ensuring that these categories align with established consumption criteria.

Response 11: We appreciate this point. We agree that these variables are secondary and do not directly support conclusions about the intervention’s primary effect. For this reason, we further reduced their prominence and framed them strictly as contextual or exploratory. At the same time, we clarified the operational definitions used for substance-use categories in the Methods section. Specifically, all substance-use and gambling variables referred to the past 3 months; non-daily cannabis use was defined as monthly use (1–4 times per month) during this period, and daily use as everyday use. We also clarified how parental alcohol and cannabis use variables were coded.

Comment 12: Results

The Results section appears to focus mainly on the secondary objectives, while only one paragraph presents findings related to the primary objective. If the authors consider this section too brief, additional analyses — for example, stratification by sex or other relevant variables — could strengthen the evaluation of the intervention’s main objective.

Response 12: We thank the reviewer for this helpful suggestion and agree that the original Results section placed too much emphasis on secondary descriptive information. In response, we restructured the Results section to give substantially greater prominence to the primary outcome. We now present the overall pre- and post-intervention knowledge scores more clearly, including the median paired change, the proportion of students who improved, the Hodges–Lehmann estimate with 95% confidence interval, and the effect size. We also added exploratory subgroup analyses of pre–post change according to cannabis use status and according to any reported parental alcohol/cannabis use, together with corresponding figures to improve clarity and readability. By contrast, the descriptive prevalence figure was moved to the supplementary material. We did not add sex-stratified pre–post analyses, because the study was not designed or powered for multiple subgroup comparisons, but we agree that such analyses could be considered in larger controlled studies.

Comment 13: Discussion

The discussion appropriately addresses the principal objective; however, the secondary objectives are not discussed. Therefore, I recommend reconsidering their inclusion or removing them from the manuscript.

Response 13: We appreciate this observation. After revision, we chose to retain the secondary objectives only as contextual and exploratory components, but we reduced their prominence in both the Results and Discussion. In the Discussion, we now refer to them only briefly and explicitly as hypothesis-generating findings that should not be given inferential weight. We believe this approach maintains useful descriptive context while preserving the manuscript’s clear focus on the principal objective.

Comment 14: Conclusions

The conclusions are consistent with the primary objective of the study.

Response 14: We thank the reviewer for this positive assessment.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The article is acceptable in its current form.

Comments on the Quality of English Language

I would like to congratulate the authors on this important study. However, the presentation of the educational intervention, which constitutes the main hypothesis of the study, is quite weak. The results section appears to focus mainly on prevalence. Tables and analyses demonstrating the effectiveness of the education in the whole group and in subgroups are needed. For example, what were the pre- and post-education scores among those who use cannabis and other substances, and among those with a family history of substance use? What was the effect of the education on these outcomes? These analyses should be added. In addition, what is the relationship (interaction) between the increase or decrease in scores and family history of substance use? Furthermore, presenting the pre- and post-education scores with graphs would also improve the clarity and readability of the manuscript.

     

Author Response

Reviewer comment:
I would like to congratulate the authors on this important study. However, the presentation of the educational intervention, which constitutes the main hypothesis of the study, is quite weak. The results section appears to focus mainly on prevalence. Tables and analyses demonstrating the effectiveness of the education in the whole group and in subgroups are needed. For example, what were the pre- and post-education scores among those who use cannabis and other substances, and among those with a family history of substance use? What was the effect of the education on these outcomes? These analyses should be added. In addition, what is the relationship (interaction) between the increase or decrease in scores and family history of substance use? Furthermore, presenting the pre- and post-education scores with graphs would also improve the clarity and readability of the manuscript.

Response:
We sincerely thank the reviewer for the positive assessment of the study and for these helpful suggestions. We agree that the educational intervention and the pre–post knowledge outcomes needed to be presented more clearly, and we have revised the manuscript accordingly.

First, we expanded the description of the educational intervention in the Methods section. The revised manuscript now specifies that the intervention, “5 Top Secrets about Cannabis”, consisted of three standardized 1-hour classroom sessions delivered over three consecutive weeks by mental health specialist nurses. We also clarified the core educational components, including health literacy, correction of misconceptions, risk perception, cannabis potency and product diversity, peer influence, and resistance skills. In addition, we clarified that the intervention was delivered using a common facilitator script and uniform materials to support standardization and replication.

Second, we substantially revised the Results section so that the primary focus is now the pre–post change in cannabis-risk knowledge rather than prevalence alone. We added a dedicated section reporting the overall pre–post knowledge change in the full sample. Knowledge scores increased from a median of 8 to 13 out of 15, with a median paired change of +5 points, improvement in 96.7% of participants, and a large Wilcoxon effect size.

Third, in response to the reviewer’s request, we added exploratory subgroup analyses of pre–post knowledge change. These analyses now show pre- and post-education scores, median change, proportion improved, within-group p-values, and effect sizes by cannabis-use status and by reported parental alcohol/cannabis use. These results are presented in the new Table 1. We also added Supplementary Table S1 showing analogous exploratory analyses by alcohol use, amphetamine use, cocaine use, and gambling.

Fourth, to address the reviewer’s question regarding whether the magnitude of knowledge-score change differed according to family substance-use context, we conducted an exploratory comparison of individual change scores, defined as posttest minus pretest knowledge score, according to adolescent-reported parental alcohol/cannabis use. The median change was +5 points both among students with and without reported parental alcohol/cannabis use, and the between-group comparison was not statistically significant. We did not interpret this as a formal interaction analysis, and because several subgroup frequencies were small, we framed these analyses as exploratory and hypothesis-generating.

Finally, we added graphical presentations of the pre–post results to improve clarity and readability. Figure 1 now presents pre- and post-intervention knowledge scores in the full sample, and Figure 2 presents change scores according to cannabis-use status and reported parental alcohol/cannabis use. We believe these additions make the educational effect easier to interpret and respond directly to the reviewer’s concern that the previous Results section focused too heavily on prevalence.

We have also revised the Discussion to reflect these new analyses while maintaining appropriate caution. In particular, we now emphasize that, because this was a single-group pre–post study without a control group, the findings should be interpreted as short-term within-subject change in a proximal cognitive outcome under uncontrolled conditions, rather than as evidence of causal intervention effectiveness or sustained behavioral impact.