Design and registration
The protocol for the proposed systematic literature review was developed according to the Preferred Reporting Items for Systematic Review and Meta-Analyses Protocols (PRISMA-P) guidelines . For completed PRISMA-P checklist see Additional File 1. The protocol for this systematic review has been registered in the International Prospective Register of Systematic Reviews (PROSPERO) database (www.crd.york.ac.uk/PROSPERO, CRD42021229955). Any protocol amendments will be documented in the PROSPERO database.
Following the PEO (i.e. Population, Exposure, Outcome) format for systematic reviews of association (aetiology) , the primary aim of this systematic literature review will be to systematically search and narratively synthesise studies examining parental depression characteristics (exposure) and protective factors (exposure) associated with mental health resilience (outcome) in offspring exposed to parental depression (population). Findings will be synthesised and critically assessed on the following questions:
- How is mental health resilience defined in previously conducted studies?
- Are parental depression characteristics and comorbid conditions associated with mental health resilience in their offspring?
- Which child, family and social factors are associated with mental health resilience in offspring exposed to parental depression?
- Are there protective factors that are specific to offspring’s sex, developmental stage or different type of outcomes/ outcome domains?
The first question will be answered by systemising information from previous research on how mental health resilience was conceptually and operationally defined, which offspring outcome domains were examined to define resilience, and over what time period. The second question will systemise results of studies examining parental depression characteristics and comorbid conditions in relation to mental health resilience in their offspring. The third question, and the main focus of this review, will identify child, family, and social protective factors associated with mental health resilience in offspring exposed to parental depression. Finally, as a secondary aim, the review will examine if there is enough evidence to support sex-, developmental stage-, and outcome domain-specific factors associated with mental health resilience in offspring exposed to parental depression.
Identified studies will be included in the proposed systematic review if they meet the following inclusion criteria:
- The study is written in English and is published in a peer reviewed-journal.
- The study is a primary research study examining factors associated with mental health resilience in child, adolescent, or adult offspring of depressed parents/caregivers, including both observational (i.e. prospective or retrospective cohort, case-control or cross-sectional) or randomised controlled trial (RCT) study designs. Factors defined as predictors or moderators will be eligible for inclusion.
- At least one of the parents/ caregivers in the study meets clinical or research International Classification of Diseases (ICD) or Diagnostic and Statistical Manual of Mental Disorders (DSM) criteria for a depressive disorder, receives treatment for depressive disorder or reports depressive symptoms. Studies, including parents/ caregivers with comorbid conditions, using parental depressive disorder as a subgroup in the analyses or comparing its effects to other types of parental psychopathology will be eligible for inclusion.
- Study reports on mental health resilience in offspring. Studies defining mental health resilience as absence of psychopathology, absence of psychopathology and positive adjustment/ competence, and better than expected outcome will be eligible for inclusion.
Studies will be excluded if:
- The study is written in another language than English and/ or published in a not peer-reviewed journal.
- The study is a secondary research report (e.g. book chapter, review, letter, editorial, or commentary), grey literature, systematic review, meta-analysis, abstract or conference proceeding, or study employing other research designs than mentioned in the inclusion criteria.
- Parents/ caregivers participating in the study are not receiving treatment for depression or their depressive disorder or symptoms are not assessed/ clearly reported. Studies combining/ merging parental depression with other mental health conditions will also be excluded.
- Offspring mental health resilience is not clearly defined or reported.
A two-step search strategy will be performed to maximise the chances of identifying relevant studies. First, electronic searches will be performed by searching titles, abstracts, keywords, and subheadings for articles published from inception to 2021 in PsycINFO, Embase, MEDLINE, Web of Science Core Collection, and Cochrane Library. No filters will be applied. Then, additional articles will be identified by manually screening the references and citations of included studies.
Search terms that will be used in the proposed systematic literature review can be grouped into four key concepts: parents/caregivers, depression, offspring, and protective factors/ mental health resilience. Additionally, the exclusion terms will be used to eliminate secondary research reports, conference proceedings or studies employing research designs that do not meet eligibility criteria for this systematic review. The combination of terms that will be used in electronic searches is presented in Table 1. Terms and subheadings for the electronic searches were chosen on the basis of results of an initial scoping review, search terms used in previous narrative reviews on this topic, and consultation with university librarian and researchers with expertise in developmental psychopathology, mental health resilience and systematic literature reviews.
Insert Table 1 about here.
Pilot testing of the search strategy was performed prior to registering the protocol to identify the utility of selected subject headings, terms and their combinations. Ten publications relevant to mental health resilience, including literature reviews and qualitative studies, were identified prior to the pilot search. Then, electronic searches were performed to examine if search strategy used can capture relevant publications identified and exclude those that employ research designs not eligible for inclusion (i.e. systematic reviews and qualitative studies). For selected publications and pilot search results see Additional File 2, while draft search strategy for one of the databases and full search strategy for each database are presented in Table 2 and Additional File 3, respectively.
Insert Table 2 about here.
All search results will be exported from the database and imported into the reference management software EndNote™ and automatically and manually deduplicated by matching different combinations of author, title, and year of study. Following deduplication, references will be imported into systematic literature review software Rayyan  that will be used for title/abstract and full-text screening, documentation of screening progress, and reasons for exclusion. First, titles and abstracts will be screened to identify publications for full-text retrieval. If at this stage, reviewers are unsure about the eligibility of the study, it will be included in the full-text screening stage. Then, full texts of potentially eligible studies will be assessed against previously mentioned inclusion and exclusion criteria. Discrepancies between reviewers, if any, will be resolved during consensus meetings with a senior researcher (SC). Finally, additional articles will be identified by screening references and citations of studies included in the systematic review. The literature search and deduplication will be performed by the first reviewer only (EP), while title/ abstract and full-text screening of studies identified by electronic searchers and identification of additional papers will be independently done by both first and second (JMM) reviewers. Reviewers will be blinded to the other’s decisions during this process.
Two separate data extraction forms for observational studies and RCTs will be developed following Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA)  and Cochrane  guidelines. Extracted data will be compiled in an Excel sheet. For observational studies, the form will include information on study characteristics (i.e. first author and date, country of study, study design, years of follow-up, study aims), population characteristics (i.e. sample size, offspring age and sex, and time of exposure to parental depression), exposure characteristics (i.e. depressed parent’s sex and age, type and characteristics of parental depressive disorder, comorbid conditions, and assessment and diagnostic instruments used), outcome (i.e. the definition of mental health resilience, offspring’s mental health/ resilience outcome result, the timing of outcome measurement, and assessment and diagnostic instruments used), comparison group (if any), protective factors, a measure of association, p-value, covariates, if any, used in the model, main findings, limitations, and risk of bias assessment outcome.
For RCTs, aforementioned study characteristics, population characteristics (i.e. depressed parent’s age and sex, type and (baseline) characteristics of parental depressive disorder, comorbid conditions, and assessment and diagnostic instruments used), intervention characteristics (i.e. type of intervention, timing, duration, and delivery of intervention), comparison group, outcome characteristics (i.e. the definition of mental health resilience, parent’s/caregiver’s and offspring’s mental health outcome, the timing of assessment, and assessment and diagnostic instruments used), a measure of association, p-value, main findings, limitations, and risk of bias assessment outcome will be reported.
Data extraction will be performed by the first reviewer only. The second reviewer will independently validate at least 20% of the data extracted.
Risk of Bias Assessment
Risk of bias assessments will be performed separately for observational studies and RCTs. In line with recommendations, no observational studies will be excluded based on the risk of bias assessment outcome . For observational studies, Joanna Briggs Institute (JBI) critical appraisal checklists for cohort, case-control, and cross-sectional studies will be used . These critical appraisal tools consider comparability of groups, appropriateness of exposure and outcome assessments, identification and handling of confounding factors, and appropriateness of statistical analyses used. Each domain will be evaluated as being at a high, low, or unclear risk of bias or by selecting a not applicable option.
The Revised Cochrane risk of bias tool for randomised trials (RoB 2) will be used for RCTs . The risk of bias arising from the randomisation process, deviations from the intended intervention, missing outcome data, measurement of outcome data, and selection of the reported results will be judged by selecting one of five options (Yes; Probably Yes; Probably No; No; No Information).
The risk of bias assessment will be performed by the first reviewer only, but as a reliability check, the second reviewer will independently perform risk of bias assessment of at least 20% of the studies. Cohen’s Kappa coefficient will be calculated to assess inter-rater agreement between two reviewers.
Due to expected heterogeneity across studies in terms of definitions of mental health resilience, protective factors, study designs (e.g. RCTs, observational), and outcome assessment tools, meta-analysis will not be attempted in this systematic literature review. Therefore, a narrative synthesis of data extracted from the selected studies will be performed. First, the descriptive characteristics of the included studies will be reported. These will include countries of studies, years of publication, study designs, the risk of bias assessment outcomes, population description (offspring sex, age, and time of exposure to parental depression), and exposure description (parental depression chronicity, severity, and time of onset). Then, to address the primary and secondary research questions of this review, the main findings will be presented in six major sections:
- Definition of mental health resilience in previously conducted studies.
- Parental/ caregiver factors associated with offspring mental health resilience, such as (improvement in) parental depression characteristics and/ or (absence of) comorbid conditions.
- Family factors associated with mental health resilience.
- Social factors associated with mental health resilience.
- Child factors associated with mental health resilience (i.e. biological, psychological, and lifestyle factors).
- Sex-, developmental stage-, and outcome- specific factors associated with mental health resilience.
Considering that depressive symptoms may reflect general distress rather than depressive disorders [39, 40], results of studies reporting depressive symptoms and depressive disorders in parents/ caregivers will be reported separately.