Associations between peer victimization, depressive symptoms, and suicidal ideation: investigating biological underpinnings
Bibliographic record
Abstract
Peer victimization has consistently been linked to depression and suicidal ideation in adolescence with persisting associations in adulthood. Peer victimization has been defined as harm caused by peers outside the norms of appropriate conduct (e.g., being insulted, harassed, robbed, or hit). This thesis is based on three manuscripts (henceforth referred to as Chapters 1, 2, & 3), and aimed to fill specific gaps in the literature regarding the associations between peer victimization with depressive symptoms and suicidal ideation by using two population-based cohorts; Quebec Longitudinal Study of Child Development (QLSCD) and the 1958 British Birth Cohort (1958BBC). Firstly, it is unclear whether a newer form of peer victimization expressed through electronic devices; cybervictimization, is similarly associated to suicidal ideation, compared to face-to-face peer victimization. Using the QLSCD, Chapter 1 showed that both face-to-face and cybervictimization were cross-sectionally associated to suicidal ideation throughout adolescence, but the magnitude of association was stronger for cybervictimization. Being cybervictimized only or in combination with face-to-face victimization was linked to a higher risk of reporting suicidal ideation, compared to being face-to-face victimized only. However, while face-to-face victimization predicted suicidal ideation 2 years later, cybervictimization was not a predictor after adjusting for baseline suicidal ideation. Secondly, little is known about the biological mechanisms behind the associations between peer victimization with depressive symptoms and suicidal ideation. Several biomarkers, including genetic variants and DNA methylation sites, have been studied in association with peer victimization, depressive symptoms, and suicidal ideation, independently. However, the literature is largely inconsistent, and lacking in the context of peer victimization. Building on Chapter 1 as well as prior findings with QLSCD showing that peer victimization was also associated to depressive symptoms, we sought to further understand who is more at-risk. In Chapter 2, we used a novel marker of genetic vulnerability for depression, the polygenic risk score for depression (PRS-depression), and test whether it influenced the associations between peer victimization, depressive symptoms, and suicidal ideation in adolescence. Chapter 2 results showed that PRS-depression was associated with depressive symptoms in adolescence but did not interact with peer victimization in predicting depressive symptoms or suicidal ideation. Another potential mechanism at the interface between the environment and genetics; epigenetics, was explored using epigenetic indices of biological aging (Horvath, Skin & Blood, and PedBE clocks), epigenetic pace of aging (DunedinPACE), and stress response reactivity (Epistress score). Thirdly, some studies have investigated Horvath epigenetic age in association with early life adversity, depressive symptoms, and suicidal ideation, with inconsistent findings. In addition, few have explored whether epigenetic age partly explained the associations of peer victimization with depressive symptoms and suicidal ideation. Chapter 3 used a two-cohort design using the QLSCD and the 1958BBC with information on depressive symptoms and suicidal ideation in adolescence and adulthood. Our findings unraveled some associations between epigenetic aging, as well as the DunedinPACE score, and depressive symptoms. However, no association was found between epigenetic indices and peer victimization, or suicidal ideation, hence there was no evidence of epigenetic mediation. Overall, this thesis has expanded on studies investigating peer victimization in association with depressive symptoms and suicidal ideation, specifically on potential underlying biological mechanisms, and clarifying the associations with cybervictimization
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.005 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".