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Cited by 36Genetic Associations and EpidemiologyChild and Adolescent Psychosocial and Emotional DevelopmentMental Health Research Topics

Stressful life events increase the risk of major depressive episodes: A population-based twin study

Open access
Bjørndal, Ludvig D., Kendler, Kenneth S., Reichborn-Kjennerud, Ted, Ystrom, Eivind·2023·Psychological Medicine
DOI 10.1017/s0033291722002227PMC PMC10476058
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Abstract

Background: Previous studies have found that stressful life events (SLEs) are associated with an increased risk of adult depression. However, many studies are observational in nature and limited by methodological issues, such as potential confounding by genetic factors. Genetically informative research, such as the co-twin control design, can strengthen causal inference in observational studies. Discrete-time survival analysis has several benefits and multilevel survival analysis can incorporate frailty terms (random effects) to estimate the components of the biometric model. In the current study, we investigated associations between SLEs and depression risk in a population-based twin sample (N = 2299). Methods: A co-twin control design was used to investigate the influence of the occurrence of SLEs on depression risk. The co-twin control design involves comparing patterns of associations in the full sample and within dizygotic (DZ) and monozygotic twins (MZ). Associations were modelled using discrete-time survival analysis with biometric frailty terms. Data from two time points were used in the analyses. Mean age at Wave 1 was 28 years and mean age at Wave 2 was 38 years. Results: SLE occurrence was associated with increased depression risk. Co-twin control analyses indicated that this association was at least in part due to the causal influence of SLE exposure on depression risk for event occurrence across all SLEs and for violent SLEs. A minor proportion of the total genetic risk of depression reflected genetic effects related to SLEs. Conclusions: The results support previous research in implicating SLEs as important risk factors with probable causal influence on depression risk.

AI snapshot

Written from the paper’s full text.

TL;DR

In a population-based Norwegian twin sample (N = 2299), stressful life event (SLE) occurrence was associated with increased risk of major depressive episodes, and co-twin control analyses suggested that associations for all SLEs and violent SLEs were at least partly causal. A minor share of the genetic risk of depression was linked to SLEs, with heritability falling from 58% to 50% after including all SLEs.

Key findings

  • Across all 18 SLEs, the full-sample hazard odds ratio (hOR) for depression was 1.383 [1.296–1.475], with similar within-pair estimates for DZ twins (hOR 1.398 [1.131–1.727]) and MZ twins (hOR 1.423 [1.216–1.664]).
  • Violent SLEs were associated with depression in the full sample (hOR 1.551 [1.343–1.790]) and within MZ twins (hOR 1.430 [1.032–1.982]), while the within-DZ estimate was not statistically significant (hOR 1.310 [0.797–2.155], p = 0.287).
  • Economic SLEs showed stronger within-pair associations than full-sample associations: full sample hOR 2.021 [1.524–2.681], within DZ hOR 3.307 [1.122–9.744], within MZ hOR 3.103 [1.606–5.995].
  • Other traumatic SLEs were not associated with increased depression risk in the full sample or within twin pairs; including all SLEs reduced the heritability estimate for depression from 58% to 50%, an 8% reduction.

Methods

  • Population-based twin sample from the Norwegian Institute of Public Health Twin Panel; 2299 twins responded to the Wave 2 SLE questionnaire, with mean ages 28.2 years at Wave 1 and 37.8 years at Wave 2.
  • Depression diagnoses were based on M-CIDI clinical interviews across two waves; SLEs were assessed with an 18-item questionnaire and grouped into all SLEs, relational violent SLEs, non-relational other traumatic SLEs, and economic SLEs.
  • Associations were modeled with discrete-time survival analysis using a co-twin control design and biometric frailty terms in a generalized linear mixed model; the AE model served as the basis for models incorporating SLEs.

Limitations

  • Stated limitations include that the co-twin control design cannot control for non-shared confounders affecting only one twin, the study focused on main effects rather than genotype–environment interaction, and the retrospective design leaves possible recall bias.
  • Stated measurement limitations include censoring after first MDE onset so recurrent depression was not studied, no investigation of gender-specific causes, broad SLE categories, SLE and MDE timing recorded only to the nearest year, possible long intervals between SLE and MDE onset, no assessment of long-term contextual threat, and questionnaire rather than interviewer assessment of SLEs.
  • Evident from the text: the economic SLE findings are difficult to interpret because within-pair estimates were stronger than full-sample estimates, which the authors suggest could reflect suppression in the full sample or inflation from non-shared confounding.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1017/s0033291722002227

Cites

60 of 60 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

17 of 61 cited sources checked · 14 supported · 0 flagged · accuracy not yet measured

  • Premisecitation

    Associations between SLEs and depression may in part reflect non-causal influence or confounding by genetic or familial factors.

    “However, it has been found that associations may in part reflect non-causal influence or confounding by genetic or familial factors (Brown et al., 2014; Kendler et al., 1999a; Silberg et al., 2016).”
    Quote in the paperSubstantial claim2 of 3 sources checked
    • cites Brown et al., 2014 source
    • cites Kendler et al., 1999a

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites Silberg et al., 2016 source

      In the Results (Bullying victimization and psychiatric disturbance; page unavailable), bullying was associated with young-adult depression in the full sample, but depression rates did not differ significantly between bullied and non-bullied discordant identical twins. This is consistent with possible familial confounding, but the paper does not establish genetic or familial confounding specifically for depression, and it studies bullying rather than stressful life events generally. (LLM, conf=0.84)

      Experimental — accuracy not yet measured
  • Interpretationown data

    Occurrences of violent SLEs increase depression risk when controlling for shared genetic and environmental factors.

    “We find that occurrences of violent SLEs increase depression risk when controlling for shared genetic and environmental factors, which aligns with previous studies which have assessed associations between various forms of trauma and depression risk (Brown et al., 2014; McCutcheon et al., 2009).”
    Quote in the paperSubstantial claim2 of 2 sources checked
    • cites Brown et al., 2014 source
    • cites McCutcheon et al., 2009 source
    • Rests on an assumption: Retrospective reports of SLE occurrence and the age at which SLEs occurred are accurate enough to establish temporal ordering between SLEs and depression onset.
  • Premisecitation

    All of the SLEs examined (such as assault, job loss or sexual abuse) have been implicated as risk factors for depression in genetically informative studies.

    “All of these SLEs have been implicated as risk factors for depression in genetically informative studies (Kendler et al., 1995, 2000; Kendler & Aggen, 2014; Kendler & Gardner, 2001; Kendler, Karkowski, & Prescott, 1999a).”
    Quote in the paperNot a substantial claim1 of 3 sources checked
    • cites Kendler et al., 1995, 2000

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites Kendler & Aggen, 2014 source
    • cites Kendler & Gardner, 2001 source
  • Interpretationcitation

    Findings from some previous genetically informative studies indicate that the association between economic SLEs and depression may be at least in part causal.

    “Although the inflated within-pair estimates in our study are difficult to interpret, findings from some previous genetically informative studies indicate that this association may be at least in part causal.”
    Quote in the paperNot a substantial claim1 of 2 sources checked
    • cites Kendler & Gardner, 2001 source
    • cites Kendler & Gardner, 2014 source
  • Study design and conductcitation

    The co-twin control design is unable to control for non-shared confounders that only affect one twin, which can bias estimated effects.

    “Although the co-twin control design increases control over genetic and shared environmental confounders, it is unable to control for non-shared confounders that only affect one twin, which can bias estimated effects (Frisell et al., 2012; Kendler & Gardner, 2010).”
    Quote in the paperNot a substantial claim1 of 2 sources checked
    • cites Frisell et al., 2012 source
    • cites Kendler & Gardner, 2010 source
  • Classified as probably not a substantial claim. 45
  • May combine two claims. 22
  • The quote only partly states this claim. 1

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The co-twin control design can be understood within a counterfactual model of causality.

    “The co-twin control design can be understood within a counterfactual model of causality (McAdams, Rijsdijk, Zavos, & Pingault, 2021).”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites McAdams, Rijsdijk, Zavos, & Pingault, 2021 source

  • Classified as probably not a substantial claim.

    Premisecitation

    Findings from several genetically informative studies indicate that associations between SLEs and depression in part reflect the causal influence of exposure on depression risk.

    “Findings from several genetically informative studies have indicated that the associations between SLEs and depression in part reflect the causal influence of exposure on depression risk (Kendler et al., 1999a; Kendler & Aggen, 2014; Kendler & Gardner, 2010).”
    Quote in the paperSubstantial claim2 of 3 sources checked
    • cites Kendler et al., 1999a

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites Kendler & Aggen, 2014 source
    • cites Kendler & Gardner, 2010 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Multilevel survival models can incorporate random effects (often called frailty).

    “Multilevel survival models can incorporate random effects (often called frailty; Austin, 2017).”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites Austin, 2017 source

  • May combine two claims.

    Findingcitation

    The heritability estimate for one-year depression risk was slightly lower than the estimate reported by Kendler and Gardner (2017), but close to heritability estimates for depressive symptoms in the past year and in the past two weeks.

    “The heritability estimate for one-year depression risk was slightly lower than the estimate reported by Kendler and Gardner (2017), but close to heritability estimates for depressive symptoms in the past year (Matthews et al., 2016) and in the past two weeks (Czajkowski, Røysamb, Reichborn-Kjennerud, & Tambs, 2010).”
    Quote in the paperNot a substantial claim1 of 3 sources checked
    • cites Kendler & Gardner (2017) source
    • cites Matthews et al., 2016 source
    • cites Czajkowski, Røysamb, Reichborn-Kjennerud, & Tambs, 2010 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    One previous study found a substantial genetic correlation between men and women for genetic factors influencing the propensity to experience personal SLEs.

    “Similarly, one previous study found a substantial genetic correlation between men and women for genetic factors influencing the propensity to experience personal SLEs (Bolinskey, Neale, Jacobson, Prescott, & Kendler, 2004).”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites Bolinskey, Neale, Jacobson, Prescott, & Kendler, 2004 source

      The Results report a genetic correlation of .28 between men and women for personal stressful life events. The discussion (p. 35) calls this correlation moderate and suggests that many of the same genetic factors are involved. The claim captures the shared genetic influence but overstates the correlation as substantial. (LLM, conf=0.84)

      Experimental — accuracy not yet measured

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Kendler and Gardner (2014) found that the association between financial and occupational difficulties and depression risk were stronger in male twins discordant for depression compared with female twins.

    “Kendler and Gardner (2014) found that the association between financial and occupational difficulties and depression risk were stronger in male twins discordant for depression compared with female twins.”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites Kendler & Gardner, 2014 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Previous studies have found genotype-environment interactions for SLEs and depression.

    “Previous studies have, however, found genotype-environment interactions for SLEs and depression (e.g. Choi et al. 2020; Mandelli & Serretti, 2013).”
    Quote in the paperNot a substantial claim1 of 2 sources checked
    • cites Choi et al. 2020 source

      The Introduction (page unavailable) reports earlier findings that genetic susceptibility increases depression risk in the presence of stressful life events. But the citation presents Choi et al. as an example of a study that found such an interaction; its own Results (page unavailable) report non-interactive effects of polygenic risk and unit cohesion, not a genotype–stressful-life-event interaction. (LLM, conf=0.83)

      Experimental — accuracy not yet measured
    • cites Mandelli & Serretti, 2013 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Evidence of a causal effect of maltreatment in childhood on the risk of major depression was found in a recent GWAS meta-analysis using Mendelian Randomisation.

    “Evidence of a causal effect of maltreatment in childhood on the risk of major depression was also found in a recent genome-wide association study (GWAS) meta-analysis using Mendelian Randomisation (Warrier et al., 2021).”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites Warrier et al., 2021 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Previous studies have indicated that men and women share most, but not all, genetic factors that influence the risk of depression.

    “Previous studies have indicated that men and women share most, but not all, genetic factors that influence the risk of depression (Kendler, Ohlsson, Lichtenstein, Sundquist, & Sundquist, 2018; Sullivan, Neale, & Kendler, 2000).”
    Quote in the paperNot a substantial claim1 of 2 sources checked
    • cites Kendler, Ohlsson, Lichtenstein, Sundquist, & Sundquist, 2018 source
    • cites Sullivan, Neale, & Kendler, 2000 source

  • May combine two claims.

    Findingown data

    Risk of depression increased over time but was slightly reduced at later time points (older ages) in the sample.

    “Risk of depression increased over time but was slightly reduced at later time points (i.e. older ages) in the sample.”
    Quote in the paperNot a substantial claim

  • The quote only partly states this claim.

    Findingown data

    For all SLEs, the associations with depression risk were similar in size for DZ twins and MZ twins.

    “The associations were similar in size for DZ twins and MZ twins.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Retrospective reports of SLE occurrence and the age at which SLEs occurred are accurate enough to establish temporal ordering between SLEs and depression onset.

  • May combine two claims.

    Findingown data

    For other traumatic SLEs, the occurrence of one SLE was not associated with an increased risk of depression in the full sample, nor for MZ twins or DZ twins.

    “For other traumatic SLEs, the occurrence of one SLE was not associated with an increased risk of depression in the full sample, nor for MZ twins or DZ twins.”
    • Also stated in: § Discussion · plain
      “The occurrence of other traumatic SLEs was not associated with increased depression risk.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Retrospective reports of SLE occurrence and the age at which SLEs occurred are accurate enough to establish temporal ordering between SLEs and depression onset.

  • May combine two claims.

    Findingreasoning

    In any given year in the current sample, depression risk was explained by 24% genetic influences, 17% stable (time-invariant) environmental influences, and 59% unstable (time-variant) environmental influences including measurement error.

    “In any given year in the current sample, depression risk was explained by 24% genetic influences, 17% stable (time-invariant) environmental influences, and 59% unstable (time-variant) environmental influences including measurement error.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    For violent SLEs, the occurrence of one SLE was associated with increased depression risk in the full sample and for MZ twins.

    “For violent SLEs, the occurrence of one SLE was associated with increased depression risk in the full sample and for MZ twins.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Retrospective reports of SLE occurrence and the age at which SLEs occurred are accurate enough to establish temporal ordering between SLEs and depression onset.

  • May combine two claims.

    Findingown data

    For violent SLEs, the within-pair association for DZ twins was slightly attenuated compared with the within-pair estimate for MZ twins and was not statistically significant.

    “The within-pair association for DZ twins was slightly attenuated compared with the within-pair estimate for MZ twins and was not statistically significant.”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: Retrospective reports of SLE occurrence and the age at which SLEs occurred are accurate enough to establish temporal ordering between SLEs and depression onset.

  • May combine two claims.

    Findingown data

    For economic SLEs, the occurrence of one event was associated with increased depression risk in the full sample, and stronger associations were observed for MZ twins and for DZ twins.

    “For economic SLEs, the occurrence of one event was associated with increased depression risk in the full sample, and stronger associations were observed for MZ twins and for DZ twins.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Retrospective reports of SLE occurrence and the age at which SLEs occurred are accurate enough to establish temporal ordering between SLEs and depression onset.

  • May combine two claims.

    Findingown data

    Additional descriptive analyses investigating the temporal relationship between SLE occurrence and MDE onset align with the previous literature, suggesting that most SLEs occur the same year as MDE onset.

    “Additional descriptive analyses (see online Supplementary Appendix B) where we investigated the temporal relationship between SLE occurrence and MDE onset align with the previous literature, suggesting that most SLEs occur the same year as MDE onset.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Event occurrence across all 18 SLEs, of violent SLEs and of economic SLEs was associated with an increased risk of depression.

    “Event occurrence across all 18 SLEs, of violent SLEs and of economic SLEs was associated with an increased risk of depression.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The aggregate of other traumatic SLEs included fewer SLEs compared with violent and all SLEs and was substantially more heterogeneous compared with the other aggregated SLEs.

    “we note that this aggregate included fewer SLEs compared with violent and all SLEs and was substantially more heterogeneous compared with the other aggregated SLEs.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    SLEs that occur during childhood, adolescence and adulthood are all associated with an increased risk of depression.

    “SLEs that occur during childhood, adolescence and adulthood are all associated with an increased risk of depression (Sjöholm, Lavebratt, & Forsell, 2009; Tennant, 2002).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Sjöholm, Lavebratt, & Forsell, 2009 source
    • cites Tennant, 2002 source

  • Classified as probably not a substantial claim.

    Study design and conductreasoning

    The ACE model did not converge to estimate a confidence interval for the intercept estimating the C component, likely because this variance parameter was very close to 0 or negative.

    “The ACE model did not converge to estimate a confidence interval for the intercept estimating the C component (AIC = 8715.203), likely because this variance parameter was very close to 0 or negative.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductcitation

    The M-CIDI assesses DSM-IV and ICD-10 diagnoses and has good validity and reliability.

    “M-CIDI assesses DSM-IV and ICD-10 diagnoses and has good validity and reliability (Reed et al., 1998; Wittchen, Lachner, Wunderlich, & Pfister, 1998).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Reed et al., 1998 source
    • cites Wittchen, Lachner, Wunderlich, & Pfister, 1998 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductown data

    Analyses with only threshold diagnoses yielded similar results.

    “Analyses with only threshold diagnoses yielded similar results (see online Supplementary Appendix A).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Study design and conductreasoning

    Time-censoring of SLEs that occurred after depression onset means that the SLEs predicted future depression risk and no backward associations could occur.

    “The time-censoring means that the SLEs predicted future depression risk – no backward associations could occur.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Retrospective reports of SLE occurrence and the age at which SLEs occurred are accurate enough to establish temporal ordering between SLEs and depression onset.

  • Classified as probably not a substantial claim.

    Study design and conductnone given

    Zygosity was determined by a combination of questionnaire items and genotyping.

    “Zygosity was determined by a combination of questionnaire items and genotyping.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Premisereasoning

    If associations weaken with genetic similarity (strongest in the full sample and weakest in MZ twins), this is indicative of genetic confounding, which is controlled for to a varying extent in within-pair estimates.

    “If the associations weaken with genetic similarity (i.e. strongest in the full sample and weakest in MZ twins), this is indicative of genetic confounding, which is controlled for to a varying extent in within-pair estimates.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Study design and conductreasoning

    Subthreshold diagnoses were treated as diagnoses of depression for the primary analyses to maximise statistical power.

    “Subthreshold diagnoses were treated as diagnoses of depression for the primary analyses to maximise statistical power.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Premisereasoning

    Weaker associations within twins compared with the full sample are indicative of confounding by early shared environment.

    “Weaker associations within twins compared with the full sample are indicative of confounding by early shared environment.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Survival analysis has benefits including the opportunity to incorporate right-censored observations in estimates of event probabilities and to study how the risk of events of interest is distributed over time.

    “Survival analysis has several benefits, including the opportunity to incorporate right-censored observations (i.e. when the time to event is larger than the period of data collection) in estimates of event probabilities and study how the risk of events of interest is distributed over time (Hox, 2010).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Hox, 2010

  • Classified as probably not a substantial claim.

    Premisecitation

    The biometric model explains phenotypic variation as influenced by additive genetic factors (A), non-additive genetic effects (D), shared environmental factors (C) and non-shared environmental factors (E).

    “The biometric model explains phenotypic variation as influenced by additive genetic factors (A), non-additive genetic effects (D), shared environmental factors (C) and non-shared environmental factors (E) (Eaves, Last, Young, & Martin, 1978; Fisher, 1918; Jinks & Fulker, 1970).”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Eaves, Last, Young, & Martin, 1978 source
    • cites Fisher, 1918

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites Jinks & Fulker, 1970 source

  • Classified as probably not a substantial claim.

    Premisereasoning

    If observed associations are equally strong in the full sample and for discordant DZ and MZ twins, this is indicative of causal influence, as within-pair estimates control for shared environmental and genetic factors (partially for DZ twins and fully for MZ twins).

    “If observed associations are equally strong in the full sample and for discordant DZ and MZ twins, this is indicative of causal influence, as within-pair estimates control for shared environmental and genetic factors (partially for DZ twins and fully for MZ twins).”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The ADE model was not estimated because previous studies have not found evidence of non-additive genetic effects for depression.

    “The ADE model was not estimated as previous studies have not found evidence of non-additive genetic effects for depression (Kendler & Prescott, 1999; Kendler, Neale, Kessler, Heath, & Eaves, 1992).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Kendler & Prescott, 1999

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites Kendler, Neale, Kessler, Heath, & Eaves, 1992

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Distinctions between relational and non-relational SLEs and economic SLEs have been used in some previous studies.

    “Distinctions between relational and non-relational SLEs and economic SLEs have been used in some previous studies (Anders, Shallcross, & Frazier, 2012; Stone et al., 2015; Ward, Kanu, & Robb, 2017).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Anders, Shallcross, & Frazier, 2012 source
    • cites Stone et al., 2015 source
    • cites Ward, Kanu, & Robb, 2017 source

  • Classified as probably not a substantial claim.

    Study design and conductreasoning

    The AE model served as the basis for subsequent models that incorporated the effects of SLEs.

    “Therefore, the AE model served as the basis for subsequent models that incorporated the effects of SLEs.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    The current study was retrospective in nature.

    “The current study was retrospective in nature.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductreasoning

    Using a questionnaire rather than trained interviewers could potentially result in higher inter-respondent variation in interpretation of the 18 SLEs, which could result in either under-reporting or over-reporting.

    “This could potentially result in higher inter-respondent variation in interpretation of the 18 SLEs (e.g. for sexual abuse), which could result in either under-reporting or over-reporting.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    The current study did not assess long-term contextual threat.

    “Additionally, previous studies have shown that high long-term contextual threat increases MDE onset following SLE occurrence substantially (Kendler et al., 1998), but we did not assess long-term contextual threat in the current study.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Interpretationcitation

    The current study's results are in agreement with previous studies that suggested causal influence for specific SLEs, although the current study analysed aggregated SLEs.

    “Our results are in agreement with the findings of with these previous studies, although we analysed aggregated SLEs.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductown data

    While the study adjusted for sex in the statistical models, it did not investigate if there were different causes of life events and depression by gender.

    “While we adjusted for sex in the statistical models, we did not investigate if there were different causes of life events and depression by gender.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Previous genetically informative studies have found increased depression risk associated with financial problems and job loss.

    “previous genetically informative studies that have found increased depression risk associated with financial problems and job loss (Kendler et al., 1999a; 2010; Kendler & Gardner, 2001; 2014).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Kendler et al., 1999a; 2010; Kendler & Gardner, 2001; 2014

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductreasoning

    The effects could have been different if the timing of SLE occurrence was recorded closer to the MDE onset.

    “Thus, the effects could have been different if the timing of SLE occurrence was recorded closer to the MDE onset.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductreasoning

    The possible influence of recall bias (that current depression or mood states affects correct reporting of previously experienced SLEs or depressive episodes) cannot be excluded.

    “Therefore, the possible influence of recall bias (i.e. that current depression or mood states affects correct reporting of previously experienced SLEs or depressive episodes) cannot be excluded.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The SLEs of the current study did not fit neatly into existing typologies such as the independent/dependent SLE categorisation.

    “The SLEs of the current study did not fit neatly into existing typologies such as the independent/dependent SLE categorisation (Kendler, Karkowski, & Prescott, 1999b).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Kendler, Karkowski, & Prescott, 1999b

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Causal influence on the risk of depression has been suggested for a number of specific SLEs included in the current study, such as assault, sexual abuse, and romantic problems and job loss.

    “Causal influence on the risk of depression has been suggested for a number of specific SLEs included in the current study, such as assault (Kendler et al., 1999a, 2010), sexual abuse (Kendler et al., 2000; Kendler & Aggen, 2014; Nelson et al., 2002), and romantic problems and job loss (Kendler & Gardner, 2001).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Kendler et al., 1999a, 2010

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites Kendler et al., 2000; Kendler & Aggen, 2014; Nelson et al., 2002

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites Kendler & Gardner, 2001 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The risk of psychiatric disorders is higher for childhood sexual abuse that involves intercourse compared with nongenital sexual abuse.

    “For instance, it has been found that the risk of psychiatric disorders is higher for childhood sexual abuse that involves intercourse compared with nongenital sexual abuse (Kendler et al., 2000).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Kendler et al., 2000 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Using a similar design as in the current study, Kendler and Gardner (2001) found that MZ twins with a history of depression reported higher rates of job loss compared with non-depressed co-twins.

    “Using a similar design as in the current study, Kendler and Gardner (2001) found that MZ twins with a history of depression reported higher rates of job loss compared with non-depressed co-twins.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Kendler & Gardner, 2001 source

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Previous genetically informative studies have found increased depression risk associated with combat exposure and somatic illness/injury.

    “previous genetically informative studies, which have found increased depression risk associated with combat exposure (Koenen et al., 2003) and somatic illness and injury (Kendler et al., 1999a).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Koenen et al., 2003 source
    • cites Kendler et al., 1999a

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Most studies have found that SLEs primarily increase depression risk over a shorter time period (e.g. months).

    “Most studies have found that SLEs primarily increase depression risk over a shorter time period (e.g. months; Kendler, Karkowski, & Prescott, 1998, 1999a).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Kendler, Karkowski, & Prescott, 1998, 1999a

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductnone given

    Although SLEs were time-censored so that only SLEs occurring before depression were included in analyses, SLE occurrence and MDE onset were recorded to the nearest year.

    “Although SLEs were time-censored so that only SLEs occurring before depression were included in analyses, SLE occurrence and MDE onset were recorded to the nearest year.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    Diagnoses of depression were based on repeated clinical interviews across two waves of measurements.

    “Diagnoses of depression were based on repeated clinical interviews across two waves of measurements.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductreasoning

    The analyses could have included SLEs with long timespans between SLE occurrence and MDE onset, and the relationship between SLE exposure and depression onset with long time intervals is less clear.

    “In addition, our analyses could have included SLEs with long timespans between SLE occurrence and MDE onset (as long as the SLE occurred before the diagnosis), and the relationship between SLE exposure and depression onset with long time intervals is less clear.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Previous studies have shown that high long-term contextual threat increases MDE onset following SLE occurrence substantially.

    “Additionally, previous studies have shown that high long-term contextual threat increases MDE onset following SLE occurrence substantially (Kendler et al., 1998), but we did not assess long-term contextual threat in the current study.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Kendler et al., 1998 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    The study assessed SLEs using a questionnaire and not, for instance, using trained interviewers.

    “We assessed SLEs using a questionnaire and not, for instance, using trained interviewers.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Several previous genetically informative studies have implicated economic SLEs as risk factors for depression, but not specifically reported on within-pair estimates of the associations.

    “Several previous genetically informative studies have implicated economic SLEs as risk factors for depression, but not specifically reported on within-pair estimates of the associations (Kendler et al., 1999a, 2010; Kendler & Halberstadt, 2013).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Kendler et al., 1999a, 2010; Kendler & Halberstadt, 2013

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisenone given

    Some of the SLEs included in the study (e.g. job loss) are indirectly influenced by policy.

    “Some of the SLEs included in our study (e.g. job loss) are indirectly influenced by policy and our findings underline the importance of preventing SLEs, when possible.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductreasoning

    Participants were censored after the first onset of a MDE, and so the study did not study the effects of SLEs on recurrent depression.

    “Participants were censored after the first onset of a MDE, and so we did not study the effects of SLEs on recurrent depression.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Some SLEs, like sexual abuse, affect women and men with different frequencies.

    “Some SLEs, like sexual abuse, affect women and men with different frequencies (Barth, Bermetz, Heim, Trelle, & Tonia, 2013).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Barth, Bermetz, Heim, Trelle, & Tonia, 2013 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductreasoning

    Several SLE categories were relatively broad, e.g., 'sexual abuse', and may therefore capture events with different relationships to depression risk.

    “Several SLE categories were relatively broad, e.g., ‘sexual abuse’, and may therefore capture events with different relationships to depression risk.”
    Quote in the paperNot a substantial claim
58 of 58

  • The paper relies on this without support.

    Many observational studies of risk factors for illness are limited by methodological issues such as potential confounding by genetic or environmental factors and reporting bias.

    “Many observational studies are limited by methodological issues, such as potential confounding by genetic or environmental factors and reporting bias.”

  • The paper relies on this without support.

    Retrospective reports of SLE occurrence and the age at which SLEs occurred are accurate enough to establish temporal ordering between SLEs and depression onset.

    “If a participant answered yes for any SLE, he or she was asked to enter the age (in years) when the event was experienced (or when it was first experienced if it had occurred multiple times).”
2 of 2

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • Life stress likely causally contributes to risk for depression.

    “Life stress likely causally contributes to risk for depression (e.g., Bjørndal et al., 2023), and it may set up content moderators to utilize unhelpful coping with work-related stress.”

    From I've Seen Enough: Measuring the Toll of Content Moderation on Mental Health (2025) · cites this paper as Bjørndal et al., 2023

Cites

Flagged first, then by citations

Research works printed but not linked: 1

  1. Wittchen, 1997, DIA-X Interview (M-CIDI)

Cited by

Sorted by citations

Related

Authors
Bjørndal, L. D., Kendler, K. S., Reichborn-Kjennerud, T., & Ystrom, E.
Affiliations
  • University of Oslo (NO)
  • Virginia Commonwealth University (US)
Corresponding author
Bjørndal, Ludvig D.
ORCID
Venue
Psychological Medicine
Publisher
Cambridge University Press (CUP)
Published
2022-08-03
Volume
53
Issue
11
Pages
5194-5202
ISSN
  • 0033-2917 (ISSN-L)
  • 1469-8978
DOI
10.1017/s0033291722002227
PMC
PMC10476058
OpenAlex
W4289544790
Semantic Scholar
20219665b27c2ef13a98998e1998dd5d3eeae39a
Cited by
35
References
60
Citations by year
2026: 10 · 2025: 11 · 2024: 10 · 2023: 3 · 2022: 1
FWCI
3.36
Type
journal article
Language
en
Open access
Licence
Locations
  • Psychological Medicine (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • PubMed Central (submittedVersion, cc-by)
  • NORA - Norwegian Open Research Archives (submittedVersion, other-oa)
  • PsyArXiv (OSF Preprints) (submittedVersion, cc-by)
  • PsyArXiv (OSF Preprints) (submittedVersion)
  • NORA - Norwegian Open Research Archives (submittedVersion, cc-by)
Funders
  • Norges Forskningsråd (262177; 288083)
  • H2020 European Research Council (818425)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Genetics › Genetic Associations and Epidemiology
  • Social Sciences › Psychology › Clinical Psychology › Child and Adolescent Psychosocial and Emotional Development
  • Social Sciences › Psychology › Experimental and Cognitive Psychology › Mental Health Research Topics
Keywords
life events, major depressive episode, depression risk, co-twin control, dizygotic twins, monozygotic twins, causal inference
MeSH terms
Frailty, Adult, Depressive Disorder, Major, Major Depressive Disorder, Diseases in Twins, Humans, Life Change Events, Risk Factors, Twins, Dizygotic, Twins, Monozygotic

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Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-14.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-14.

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