Contribution
A short review asking whether trauma-induced DNA methylation changes pass from parents to children in humans. It finds two parent–child studies and three of stress in pregnancy, summarises each with its limitations, and recommends larger, genome-wide, multi-centre studies. It is the record’s only account so far of what the Holocaust FKBP5 study (Yehuda et al. 2016) found, as distinct from what its critics say of it.
Key insight
The offspring do not carry their parents’ mark. In Yehuda et al., survivors had higher FKBP5 intron 7 methylation and their offspring lower. The authors call this “perplexing” and suggest “biological accommodation” or a “compensatory mechanism” (§2, §4). If so, what reaches the child is a response to the parent’s state, not a copy of it.
Assumptions
- “Transgenerational” in the loosest sense (§1). Defined as “the transmission of genomic information (in this paper DNA methylation) from one generation to the next”. Exposure in utero and exposure before pregnancy both count.
- Two designs, two mechanisms (§1). When trauma precedes pregnancy, “methylation changes to the mothers’ DNA is a necessity for the transmission”. When it occurs during pregnancy, the mother’s change is not needed. The review speaks of mothers only.
- Candidate genes of the stress axis. Every study reviewed measures methylation at a glucocorticoid-related gene (NR3C1, NR3C2, FKBP5) in blood.
Key results
- Scope (§1). PubMed from inception to March 2018. Search terms, inclusion criteria and a count of screened papers are not given.
- Rwanda (§2; Perroud et al. 2014). 25 widows pregnant during the
genocide and their children; 25 Rwandan women pregnant at the time but
living abroad, and their children.
- Exposed mothers and children had more PTSD and depression.
- Higher methylation at NR3C1 exon 1F (CpG3–CpG9); no difference at NR3C2.
- Lower cortisol in exposed mothers and children. NR3C1 methylation correlated negatively with plasma glucocorticoid levels.
- Limits the authors name: small sample; groups in different countries; no stated matching; health in pregnancy, “parenting style”, alcohol, tobacco and diet not controlled.
- Holocaust (§2; Yehuda et al. 2016). 32 survivors and their 22
offspring; 8 control subjects and their 9 offspring. Blood FKBP5
methylation and cortisol.
- FKBP5 intron 7 methylation “significantly higher” in survivors and “significantly lower” in their offspring.
- Limits named: sample size; survivors’ “extreme starvation”, which “could have also contributed to the effect seen”.
- “If further replicated in a larger study, these findings could change the way our field conceptualizes trauma and PTSD.”
- Stress in pregnancy (§3).
- Congo (Mulligan et al. 2012): in 25 mother–newborn dyads, prenatal stress correlated with newborn NR3C1 promoter methylation and with low birth weight. War stress accounted for 35% of birth-weight variance (r = −0.62, p = 0.0009); rape alone for 31%.
- Intimate partner violence (Radtke et al. 2011): violence during pregnancy was associated with NR3C1 methylation in children aged 10–19; the mother’s own methylation was not associated with it. 25 participants; violence recalled retrospectively.
- Rodney and Mulligan 2014 (Congo) is cited in §4 for the same association in newborns.
- Discussion (§4). The authors say the studies “suggest that children of parents who had suffered from extreme trauma have methylation modifications”, and that “this PTSD risk can be passed from generation to generation”. They cite Agouti diet studies in mice as support. Weaknesses: few studies, small samples, possible publication bias, unmeasured confounds, cross-sectional designs.
- Recommendations (§4, §5). Larger studies with controls; record whether trauma preceded or occurred in pregnancy, and the trimester; distinguish chronic from acute trauma; move from candidate genes to well-powered genome-wide studies, as the NIMH genomics workgroup advises; share data across centres.
Claims
| id | claim | strength | support |
|---|---|---|---|
| C1 | Children of parents exposed to extreme trauma show methylation differences at stress-axis genes | weak: two small parent–child studies, both cross-sectional, in different populations | §2, §4 |
| C2 | Holocaust survivors’ offspring show FKBP5 intron 7 methylation opposite in direction to their parents’ | weak: one study, 22 exposed offspring and 9 control offspring, as reported here | §2 |
| C3 | Maternal stress in pregnancy is associated with NR3C1 methylation in the child | weak to moderate: three small studies agree in direction | §3, §4 |
| C4 | Trauma-induced methylation changes are transmitted from parents to children | weak: the review’s conclusion outruns its evidence; no study separates transmission from shared or in utero exposure | §4, §5 |
| C5 | The field needs larger, genome-wide, multi-centre studies that record the timing of trauma | a recommendation | §4, §5 |
Concepts
- transgenerational epigenetic transmission (the authors’): passing DNA methylation states from one generation to the next without sequence change, in utero exposure included.
- biological accommodation: the authors’ gloss on offspring methylation opposite to the parent’s, a compensating response.
- NR3C1: the glucocorticoid receptor gene. FKBP5: a moderator of glucocorticoid receptor activity.
Connections
- Yehuda et al. 2016 (LIT-1692), the original. This review gives its sample, tissue, gene region, direction of effects and one named confound. Its title says “intergenerational”; the review’s says “transgenerational”.
- Bird (NOTE-1264) calls the study “a sample of only 32 people”. By this review’s figures, 32 is the number of survivors; the study had 71 people in all, 31 of them offspring.
- Heard and Martienssen (NOTE-1254). By their rule, every study here is intergenerational. The Rwandan, Congolese and partner-violence children were exposed in utero. Survivors’ children, if conceived after the war, are F1 of exposed parents.
- Horsthemke (NOTE-1265) asks that genetic effects be excluded by haplotype. Nothing here says whether FKBP5 genotype was considered.
- The Dutch Hunger Winter (LIT-1751). The review raises the survivors’ starvation as a confound; the record’s womb route already links famine to methylation.
- Yehuda and Lehrner (LIT-1715) is the clinical side of the same group; not cited here.
Bearing on the record
- The question (QUESTION-297). Four points.
- Where it sits. The record files Yehuda et al. under the germline route. On this account it is an intergenerational, parent-to-child study in blood. Nothing in it reaches a gamete, and nothing excludes the womb (for mothers), care, or shared hardship. It belongs with the “parenting” and “womb” routes as much as the germline one.
- What passes is not a copy. Offspring methylation went the other way from the parents’. That fits a child’s physiology adjusting to a parent’s state, by any route, better than a mark inherited unchanged. This is an inference from the direction, which the review reports without analysis.
- The human molecular evidence, as of 2018, is small. Two parent–child studies (25 + 25 pairs; 32 + 22 against 8 + 9) and in-utero studies of 25 each, with a third cited without numbers. All are cross-sectional and candidate-gene.
- No study measured the social routes. “Parenting style” is listed as an uncontrolled confound in Rwanda; the Holocaust study’s named confound is starvation. Neither measured care, silence, or identification with the group’s history. The question’s social routes are unexamined here, not excluded.
- The owner’s thesis (CLAIM-491). Not touched. What these studies measure is a physiological state in blood, not any identification with an ancestor. No note on the claim is proposed.
- Proposed dated note on QUESTION-297 (below, section 4).
- No THEORY filed.
- No ML instruction.
Limitations
- Not the 2016 paper. CpG sites, statistics, effect sizes, ages, sex of the exposed parent, who the controls were, genotype, cortisol relationships and the offspring’s own trauma and PTSD are not here.
- A thin review. Five studies, no search strategy, no quality assessment, no tables. Its conclusion (“accumulating evidence”) is warmer than its own list of weaknesses.
- Loose use of “transgenerational”, against the original’s own word, “intergenerational”, and against the record’s sceptical readings.
- The Agouti citation is given as support for “robust impact on stress-related disorders”; it concerns diet and coat colour in mice.
- Errors.
- “The genocide took place in 1995” (§2); the Rwandan genocide was in 1994.
- The rationale for metabolic syndrome in survivors’ offspring (§4) cites a study titled “Maternal exposure to the holocaust and health complaints in offspring”; whether it reports metabolic syndrome is not checked here.
- Typos. “Offsprings” (title); “Radtke al” for “Radtke et al.” (§3); “promotor” (§3); “thought the reviewed studies” for “though” (§3); “methylation changes … is a necessity” (§1); “dietary supplements … was associated” (§4); “the environmental transgenerational effects … has” (§4); “not necessary PTSD alone” (§4); “Lockwood, Su, Hao, and Rutten declares” (Conflicts of Interest).
Open questions
- Was FKBP5 genotype controlled in Yehuda et al.? Horsthemke’s one feasible human step is the haplotype test.
- Were survivors’ offspring conceived after the war, and did the effect differ by which parent was exposed? Both decide which route the study can speak to.
- Does offspring methylation track the offspring’s own childhood experience of a survivor parent? If it does, the parenting route is the likelier carrier.