A Protocol for a Systematic Review of the Prevalence and Patterns of Substance Use and Related Disorders Among Children and Adolescents in South Pacific Nations

Abstract

Substance use among children and adolescents is a significant public health concern, with early initiation linked to adverse mental health, developmental, and longer-term health outcomes. In the South Pacific, substance use is shaped by distinct socio-cultural, economic, geographic, and structural conditions, including traditional practices such as betel nut use and the challenges of delivering services across island communities. Although research has examined substance use among young people in the region, the literature remains heterogeneous and fragmented. No comprehensive synthesis has yet focused specifically on children and adolescents across South Pacific nations. This systematic review will synthesise evidence on the prevalence, patterns, and determinants of substance use and SUDs among children and adolescents in South Pacific countries. Searches will be conducted across MEDLINE, Embase, PsycINFO, CINAHL, and the Cochrane Library for publications from 2000 to 2026. Grey literature in region-focused repositories will also be searched. Observational studies reporting quantitative data on substance use among people aged 10–18 years will be included. Two reviewers will independently screen studies, extract data, and assess methodological quality using the Joanna Briggs Institute Critical Appraisal Checklist for Prevalence Studies. If sufficiently comparable data are available, meta-analysis will be conducted using random-effects models; otherwise, findings will be synthesised narratively.

1. Introduction

Substance use and substance use disorders (SUDs) among children and adolescents are important public health concerns globally and within the South Pacific region [1,2]. Early initiation is associated with long-term dependence, adverse mental health outcomes, and broader psychosocial consequences across the life course [1,2,3,4]. Because adolescence is a period of rapid biological, psychological, and social change, substance use during this stage can shape later patterns of health, education, and social participation.

Importantly, clinically defined SUD captures only part of the burden of substance use in children and adolescents. Adult-derived diagnostic criteria may be less applicable in younger populations, in whom shorter exposure histories can limit the expression of features such as tolerance, withdrawal and sustained impairment [5]. Nevertheless, substance exposure during adolescence occurs during ongoing maturation of neural systems involved in reward processing, executive control and decision-making, potentially increasing vulnerability to adverse outcomes [6,7,8]. Earlier initiation is also associated with greater risk of subsequent problematic use and SUD [9]. Accordingly, assessment of substance use across the spectrum, rather than SUD alone, is particularly important in this population.

Most evidence on youth substance use comes from high-income Western settings. Although this work has informed understanding of prevalence, risk factors, and prevention strategies, its relevance to the South Pacific is limited by differences in culture, geography, health-system capacity, and local substance use practices. In this region, behaviours are shaped by traditional practices, communal social structures, uneven access to services, and the realities of small island and remote communities. As highlighted in previous protocol-based reviews [10], organising risk and protective factors within specific populations is essential for developing prevention strategies that are genuinely relevant to local contexts.

The region encompasses diverse Indigenous peoples, languages, colonial histories, customary governance systems, and social practices. Kinship and communal obligations may be relevant across several island settings, but neither a single shared culture nor a uniform pattern of substance use can be presumed with substance use [11].

Evidence from South Pacific nations has grown through school-based surveys, community samples, and population-level assessments [12,13,14,15,16]. A recent systematic review of substance abuse across South Pacific populations reported wide variation in prevalence estimates, prominent tobacco and betel nut use, limited data on co-occurring disorders and polysubstance use, and a need for culturally sensitive and standardised surveillance [17]. However, the youth-specific literature remains difficult to interpret. Studies vary in age ranges, schooling status, recruitment settings, measurement tools, definitions of substance use and disorder, and analytical approaches. This variability limits comparability across studies and makes it harder to build a coherent picture of substance use among children and adolescents in the region.

Substance use among South Pacific youth is likely shaped by overlapping individual, social, cultural, and structural influences. Peer exposure, social modelling, family environments, and community norms have been linked with tobacco and betel nut use among adolescents [13,18,19]. Broader factors, including economic disadvantage, intergenerational trauma, and the continuing effects of colonisation, may also shape patterns of use and related harms [18,19,20,21]. These influences sit within a regional context marked by limited access to healthcare, under-resourced mental health systems, and the geographical isolation of many island communities. The archipelagic nature of the South Pacific creates practical barriers to surveillance, research, and service delivery, especially in rural and remote settings where routine data systems may be limited or absent.

Despite growing research activity, no comprehensive synthesis has focused specifically on children and adolescents in South Pacific nations. Important gaps therefore remain in understanding overall prevalence, patterns across substances and demographic groups, and the developmental pathways through which early use may become harmful. There is also limited synthesis of the relationship between substance use and mental health outcomes in this population, despite well-established associations in other settings. Similar gaps relating to co-occurring disorders and polysubstance use have previously been identified within broader South Pacific substance use research [22]. As noted in comparable contemporary protocols [16], integrated evidence is needed to identify modifiable risk and protective factors and inform contextually appropriate interventions.

Pacific Islander populations remain underrepresented in substance use research and, when included, are often grouped into broad ethnic or regional categories. This can obscure important within-group differences and limit the ability to identify disparities across specific populations [22,23,24,25]. The lack of disaggregated, youth-specific data adds further uncertainty to estimates of the burden of substance use and related disorders in the region.

These limitations justify a focused and transparent synthesis of the existing literature. The review will clarify the epidemiology of substance use among children and adolescents in South Pacific nations, identify key determinants and patterns of use, and examine how methodological variability influences reported findings. A consolidated evidence base will support culturally appropriate prevention, early intervention, and treatment strategies that reflect the socio-cultural and structural contexts of the region.

2. Objectives

This protocol describes a systematic review of substance use and SUDs among children and adolescents in South Pacific nations. Given the heterogeneity of the current literature, the review aims to clarify the epidemiology, patterns, and determinants of substance use in this population.

Specifically, the objectives of this systematic review are to:

• Identify and synthesise the prevalence of substance use and SUDs among children and adolescents (aged 10–18) across South Pacific nations, including variation across substances such as alcohol, tobacco, betel nut, cannabis, and emerging psychoactive substances.
• Examine patterns of substance use within this population, including frequency of use, age of initiation, and evidence of polysubstance use, where reported.
• Assess variation in substance use across demographic and socio-cultural subgroups, including age, sex, ethnicity, and geographic setting, to identify potential disparities within and between populations.
• Identify individual, social, and structural factors associated with substance use, including peer influences, family environment, socio-economic conditions, cultural practices, and broader contextual determinants.
• Explore the relationship between substance use and mental health and developmental outcomes, where such associations are reported in the literature.
• Evaluate the extent to which methodological differences across studies, including study design, sampling strategies, and measurement approaches, may influence reported prevalence estimates and observed associations.

The proposed systematic review will address the following research questions:

• What is the prevalence of substance use and SUDs among children and adolescents in South Pacific nations?
• How do patterns of substance use vary by substance type and demographic characteristics within this population?
• What factors are associated with substance use among youth in the South Pacific region?
• What is the relationship between substance use and mental health outcomes in this population?
• How do methodological variations across studies impact the interpretation of prevalence and associated findings?

The findings of this review are intended to inform the development of culturally appropriate, evidence-based prevention and early intervention strategies, as well as to guide future research priorities within the South Pacific context.

3. Methods

3.1. Protocol Reporting Guidelines and Registration

This systematic review protocol has been developed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis Protocols (PRISMA-P) guidelines [26].

The protocol has been registered with the International Prospective Register of Systematic Reviews (PROSPERO) (registration number: CRD420261376977). Any amendments to the protocol will be documented, dated, and reported in the final manuscript.

3.2. Eligibility Criteria

Studies will be eligible for inclusion if they examine substance use among children and adolescents within South Pacific nations. For this review, the youth population will be defined as individuals aged 10–18 years. This age range aligns with commonly used definitions of adolescence and with youth substance use research in public health and epidemiology [27,28], particularly studies examining early initiation and developmental trajectories [28].

Studies that include broader age ranges will be considered where data for the specified youth population can be extracted separately.

The review will include studies reporting on substance use behaviours and SUDs, including but not limited to:

• Alcohol.
• Tobacco (including smoked and smokeless forms).
• Betel nut (areca nut).
• Cannabis.
• Kava.
• Emerging or synthetic psychoactive substances.

Outcomes

The primary outcome will be:

• Prevalence of substance use and SUDs.

Secondary outcomes will include:

• Patterns of substance use (e.g., frequency, age of initiation).
• Polysubstance use.
• Associated risk factors and determinants.
• Mental health and developmental outcomes where reported.
• Associated risk factors and determinants, categorized into socio-demographic factors (e.g., age, gender, socioeconomic status), environmental exposures, and institutional settings relevant to the target population.
• Mental health outcomes which are defined as any clinical diagnosis (e.g., anxiety, depression via ICD/DSM criteria) or validated psychometric scale scores (e.g., PHQ-9, GAD-7, SDQ) reporting on psychological distress or psychiatric morbidity.
• Developmental outcomes which are defined as objective or standardized subjective measures of cognitive, motor, language, or social-emotional milestones.

Study Design

Eligible studies will include observational designs such as cross-sectional studies, cohort studies, and population-based surveys.

Studies will be excluded if they are:

• Case reports or case series.
• Editorials, commentaries, or conference abstracts.
• Qualitative-only studies.
• Intervention studies without baseline prevalence data.

Setting

Studies conducted in South Pacific nations, including but not limited to Fiji, Papua New Guinea, Samoa, Tonga, and French Polynesia, will be included. Studies conducted in Australia, New Zealand, Hawaii, or American Samoa will be excluded because their socio-cultural and health-system contexts differ from those of the island nations that are the focus of this review. Searches will be limited to English-language publications from 2000 onwards.

3.3. Information Sources

A structured literature search will be conducted across the following electronic databases:

• Medline (via Ovid).
• Embase (via Elsevier).
• PsycINFO (via EBSCO).
• CINAHL (via EBSCO).
• Cochrane Library.

Searches will cover publications from 2000 to 2026, with an updated search performed before final analysis to capture newly published studies.

The search strategy will combine controlled vocabulary (e.g., MeSH terms) and free-text keywords across three core concepts:

• Substance use (e.g., alcohol, tobacco, betel nut, cannabis).
• Youth populations (e.g., child, adolescent, young people).
• South Pacific populations (e.g., Melanesia, Polynesia, Micronesia, and specific country names).

Search strategies will be adapted for each database. Reference lists of included studies will also be screened to identify additional relevant records.

In addition, due to the possible paucity of scientific literature emanating from this region, grey literature and institutional repositories will be searched. This will include regional repositories such as the Fiji Institute of Pacific Health Research, the Health New Zealand Research Repository, and the World Health Organization Regional Committee for the Western Pacific. As well, attempts will be made to directly contact researchers and experts working in this space.

3.4. Search Strategy

The following pilot search strategy was constructed and run in Ovid MEDLINE on 26 June 2026. It will be updated and re-run when screening commences, with adaptations for the other databases listed in Section 3.3.

(1)

substance-related disorders/or alcohol-related disorders/or alcohol-induced disorders/or alcohol-induced disorders, nervous system/or alcohol amnestic disorder/or alcoholic korsakoff syndrome/or alcohol withdrawal delirium/or alcohol withdrawal seizures/or alcoholic neuropathy/or cardiomyopathy, alcoholic/or fetal alcohol spectrum disorders/or liver diseases, alcoholic/or fatty liver, alcoholic/or hepatitis, alcoholic/or liver cirrhosis, alcoholic/or pancreatitis, alcoholic/or psychoses, alcoholic/or alcoholic intoxication/or alcoholism/or binge drinking/or amphetamine-related disorders/or cocaine-related disorders/or drug misuse/or prescription drug misuse/or drug overdose/or opiate overdose/or prescription drug overuse/or inhalant abuse/or marijuana abuse/or narcotic-related disorders/or opioid-related disorders/or heroin dependence/or morphine dependence/or opium dependence/or phencyclidine abuse/or psychoses, substance-induced/or substance abuse, intravenous/or substance abuse, oral/or substance withdrawal syndrome/or “tobacco use disorder”/332,405

(2)

drinking behavior/or alcohol drinking/or drug-seeking behavior/89,206

(3)

Cocaine/or Crack Cocaine/28,204

(4)

Cannabis/16,309

(5)

Areca/2302

(6)

(“betel nut*” or kava).ab,ti/1901

(7)

smoking/or pipe smoking/or water pipe smoking/or smoking, non-tobacco products/or cocaine smoking/or marijuana smoking/or tobacco smoking/or cigar smoking/or cigarette smoking/or vaping/or “tobacco use”/173,189

(8)

1 or 2 or 3 or 4 or 5 or 6 or 7/563,946

(9)

“Native Hawaiian or Other Pacific Islander”/or Pacific Island People/2463

(10)

(“south pacific*” or Melanesia* or micronesia* or polynesia* or fiji* or “new caledonia*” or “papua new guinea*” or vanuatu or guam or palau or pitcairn or samoa* or tonga* or “cook islands” or “solomon islands”).mp/24,190

(11)

9 or 10/26,254

(12)

(child* or youth or young or teen* or adolesc* or juvenile or pediatric or paediatric).mp/5,422,587

(13)

8 and 11 and 12/335

3.5. Data Management

Search results will be exported to EndNote for storage and deduplication. Duplicate records will be removed using automated and manual checks to maximise accuracy. Records with clearly labelled ineligible study designs will also be removed.

Following deduplication, records will be imported into the Joanna Briggs Institute System for the Unified Management, Assessment and Review of Information (JBI SUMARI) platform to facilitate study screening, eligibility assessment, data extraction, and methodological quality appraisal. Screening decisions and extracted data will be recorded and maintained within the platform throughout the review process.

Data extraction forms and review documents will be stored securely on password-protected institutional systems accessible only to the review team. Any amendments to extracted data or study classifications made during the review process will be documented to maintain transparency and reproducibility.

3.6. Selection Process

All identified records will be exported into reference management software (EndNote from Clarivate, version 21) for deduplication. Duplicate records will be removed using automated and manual processes.

After deduplication, records will be imported into JBI SUMARI. Study selection will be conducted in two stages:

• Title and abstract screening, conducted independently by two (BO and SM) reviewers.
• Full-text review of potentially eligible studies.

Disagreements between reviewers will be resolved through discussion and consensus. Where consensus cannot be reached, a third reviewer will adjudicate. A PRISMA flow diagram will be used to document the study selection process.

3.7. Data Extraction and Collection

Data will be extracted using a standardised data extraction form developed for this review. Extraction will be performed independently by two (BO and SM) reviewers.

The following variables will be collected:

-

Study characteristics: author(s), year of publication, country, and study setting (e.g., school-based, community-based, clinical setting).

-

Study design: study type (e.g., cross-sectional, cohort), sampling methods, and recruitment strategy.

-

Participant characteristics: age range, mean/median age where available, sex distribution, ethnicity, and socio-demographic context.

-

Sample size: total number of participants included in the analysis.

-

Substance types assessed: alcohol, tobacco (smoked and smokeless), betel nut, kava, cannabis, and other emerging psychoactive substances.

-

Measurement methods: type of instrument used (standardised vs. non-standardised), definitions of substance use, and timeframes (e.g., lifetime use, current use).

-

Outcomes: prevalence estimates of substance use and SUDs, including any subgroup analyses reported.

-

Patterns of use: where available, frequency of use, age of initiation, and evidence of polysubstance use.

-

Associated factors: reported individual, social, cultural, and structural risk or protective factors.

Where studies report data across broader age ranges, only data relevant to the predefined youth population will be extracted where possible. Where necessary, assumptions regarding categorisation of age groups or definitions of substance use will be documented and applied consistently across studies. Any discrepancies in data extraction will be resolved through discussion or consultation with a third reviewer.

In cases where critical data is missing, ambiguous, or insufficiently reported for extraction or meta-analysis, a protocol will be employed to contact the corresponding authors of the primary studies via email. A maximum of two contact attempts will be made over a two-week period and, if no response is received, the study will be analyzed using the available published data, and this missingness will be noted in the risk of bias assessment.

3.8. Data Outcomes and Prioritisation

The primary outcome of this review will be the prevalence of substance use and SUDs among children and adolescents in South Pacific nations. This outcome has been prioritised due to its central importance in characterising the epidemiology of substance use within this population and informing public health planning.

Secondary outcomes will include:

-

Patterns of substance use, including frequency of use, age of initiation, and duration of use where reported.

-

Polysubstance use, including concurrent or sequential use of multiple substances.

-

Subgroup differences in prevalence, including variation by age, sex, ethnicity, and geographic setting.

-

Associated risk and protective factors, including individual, social, cultural, and structural determinants.

-

Mental health and developmental outcomes, where studies report associations between substance use and psychological or behavioural outcomes.

Primary and secondary outcomes have been prioritised to ensure a comprehensive understanding of both the epidemiological burden and the broader contextual factors influencing substance use among youth. Where multiple outcomes are reported, priority will be given to prevalence estimates derived using validated or standardised measurement tools.

4. Risk of Bias in Individual Studies

The methodological quality of included studies will be assessed using the Joanna Briggs Institute (JBI) Critical Appraisal Checklist for Prevalence Studies. Risk of bias will be evaluated at the study level, given the focus on prevalence estimates.

Two reviewers will independently assess each study across domains including sampling methodology, sample size adequacy, validity and reliability of measurement tools, statistical analysis, and response rates. Discrepancies will be resolved through discussion or consultation with a third reviewer.

Risk of bias assessments will not be used as exclusion criteria however they will be incorporated into the interpretation of findings. Where appropriate, the influence of study quality on reported prevalence estimates will be explored, and sensitivity analyses may be conducted to assess the robustness of findings.

5. Data Synthesis

Where sufficient studies report comparable populations, outcomes, and measurement approaches, quantitative synthesis will be considered. Studies will be included in meta-analysis only where there is reasonable clinical and methodological homogeneity, particularly in definitions of substance use, age groups, and study design. If meta-analysis is undertaken, pooled prevalence estimates will be calculated using appropriate random-effects models, and heterogeneity will be assessed using the I² statistic.

Where data permit, subgroup analyses will be conducted to explore variation in prevalence estimates across:

-

Age groups.

-

Sex.

-

Country or subregion.

-

Substance type.

Sensitivity analyses may be conducted to assess the robustness of findings, including exclusion of studies at high risk of bias or those using non-standardised measurement tools.

Where quantitative synthesis is not appropriate due to substantial heterogeneity in study design, populations, or outcome measures, findings will be synthesised narratively. The narrative synthesis will be structured around key themes, including substance type, population characteristics, and geographic context. Results will be presented using descriptive summaries, tables, and figures where appropriate, with particular attention to identifying patterns, inconsistencies, and gaps in the evidence base.

6. Meta-Biases

Potential sources of meta-bias, including publication bias and selective reporting, will be considered during the review. Where sufficient studies are available for a given outcome, typically at least 10, publication bias will be assessed by visual inspection of funnel plots and, where appropriate, statistical tests for asymmetry such as Egger’s test.

Selective reporting bias within individual studies will be considered as part of the risk of bias assessment using the Joanna Briggs Institute Critical Appraisal Checklist for Prevalence Studies. Particular attention will be given to inconsistencies between reported methods and outcomes, incomplete reporting of prevalence estimates, and lack of clarity regarding measurement tools or definitions of substance use.

Given the expected heterogeneity in study designs, populations, and measurement approaches, meta-bias assessments will be interpreted cautiously. Where quantitative synthesis is not feasible, potential biases in the evidence base will be explored narratively, including the possibility of underreporting in remote or marginalised communities.

The potential impact of these biases on the overall findings of the review will be considered in the interpretation and discussion of results.

7. Strength and Limitations

• This review will provide a focused synthesis of substance use and SUDs among children and adolescents across South Pacific nations, addressing an important gap in the literature.
• The review will use a transparent protocol, PRISMA-P guidance, multiple databases, and independent screening and data extraction by more than one reviewer.
• The inclusion of culturally relevant substances, including betel nut and kava, will allow a more contextually grounded account of substance use in the South Pacific.
• The review will examine individual, social, cultural, and structural determinants, giving attention to the broader conditions that shape youth substance use in the region.
• Differences in age definitions, measurement tools, and study designs may limit comparability and may prevent meta-analysis for some outcomes.
• Reliance on cross-sectional and self-reported data may introduce reporting bias and limit causal interpretation.
• Restricting the review to English-language publications may exclude relevant local or regional evidence and introduce language bias.
• Uneven representation of South Pacific populations, including possible underrepresentation of remote or marginalised communities, may limit the generalisability of the findings.

8. Discussion

Substance use among children and adolescents is a significant public health concern, with early initiation associated with long-term health and psychosocial harms [1,2]. Although youth substance use has been widely studied, much of the evidence comes from high-income Western settings. In the South Pacific, existing studies suggest that tobacco, alcohol, kava, and betel nut are used by young people, often beginning during adolescence [12,13,15]. A broader regional review also indicates that prevalence estimates vary substantially across South Pacific populations and that tobacco and betel nut remain prominent substances of concern [23]. These findings have not yet been synthesised systematically with a specific focus on children and adolescents.

This review will address that gap by synthesising evidence on the prevalence, patterns, and determinants of substance use among children and adolescents in South Pacific nations. It will also consider the socio-cultural and structural contexts that shape substance use in the region. Existing research has highlighted peer influence and social norms, particularly in relation to tobacco and betel nut use [18,19]. These behaviours are further shaped by socio-economic conditions, cultural practices, family and community environments, and service access, although these factors are not consistently captured across the literature.

A key contribution of the review will be its attention to methodological variability, including differences in study design, sampling strategy, and measurement approach. This variability may influence prevalence estimates and the interpretation of associations. By examining these issues systematically, the review will help identify where future research would benefit from more consistent, culturally appropriate methods.

The review is also expected to identify gaps in the evidence, including limited data on polysubstance use, co-occurring mental health conditions, and longitudinal trajectories of substance use among young people. These gaps are important given the known links between substance use and mental health during adolescence. Pacific Islander populations also remain underrepresented in substance use research, and broad aggregation can obscure within-group differences [23,24].

The findings will have implications for research, policy, and practice. For research, the review can inform more standardised and culturally appropriate methods for studying youth substance use in the South Pacific. For policy and practice, it can support prevention and early intervention strategies that are targeted, contextually relevant, and responsive to local communities. Interventions developed in high-income Western settings may not transfer directly to South Pacific contexts, where cultural practices, community structures, geography, and service capacity shape both risks and responses.

Overall, this review is intended to provide a critically appraised evidence base for policymakers, clinicians, educators, researchers, and community stakeholders working to reduce substance-related harm among children and adolescents in the South Pacific region.