Stress-related telomere length in children: A systematic review

Accepted Manuscript Stress-related telomere length in children: A systematic review Bruno Messina Coimbra, Carolina Muniz Carvalho, Patricia Natalia Moretti, Marcelo Feijó de Mello, Sintia Iole Nogueira Belangero PII:

S0022-3956(16)30402-2

DOI:

10.1016/j.jpsychires.2017.03.023

Reference:

PIAT 3105

To appear in:

Journal of Psychiatric Research

Received Date: 19 September 2016 Revised Date:

24 March 2017

Accepted Date: 31 March 2017

Please cite this article as: Coimbra BM, Carvalho CM, Moretti PN, de Mello MF, Belangero SIN, Stressrelated telomere length in children: A systematic review, Journal of Psychiatric Research (2017), doi: 10.1016/j.jpsychires.2017.03.023. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT Stress-related telomere length in children: a systematic review Bruno Messina Coimbra a,1, Carolina Muniz Carvalho a,b,c,1, Patricia Natalia Moretti a,b,c, Marcelo Feijó de Mello a, Sintia Iole Nogueira Belangero a,b,c* a

Department of Psychiatry and Psychology, Universidade Federal de São Paulo

b

Department of Morphology and Genetics, Universidade Federal de São Paulo

(UNIFESP), São Paulo, Brazil c

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(UNIFESP), São Paulo, Brazil

de São Paulo (UNIFESP), São Paulo, Brazil 1

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These authors contributed equally to this work

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LINC, Interdisciplinary Laboratory of Clinical Neurosciences, Universidade Federal

*Corresponding author: Sintia Iole Belangero, PhD

Disciplina de Genética/ Departamento de Morfologia e Genética UNIFESP/EPM Rua Botucatu, 740, Ed. Leitão da Cunha, 1º andar, 04023-900, São Paulo, Brazil Phone: +5511-5576-4260 Fax: +5511-5579-8378

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E-mail: [email protected]

ACCEPTED MANUSCRIPT Stress-related telomere length in children: a systematic review Bruno Messina Coimbra a,1, Carolina Muniz Carvalho a,b,c,1, Patricia Natalia Moretti a,b,c, Marcelo Feijó de Mello a, Sintia Iole Nogueira Belangero a,b,c* a

Department of Psychiatry and Psychology, Universidade Federal de São Paulo

Department of Morphology and Genetics, Universidade Federal de São Paulo

(UNIFESP), São Paulo, Brazil c

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(UNIFESP), São Paulo, Brazil b

de São Paulo (UNIFESP), São Paulo, Brazil 1

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These authors contributed equally to this work

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LINC, Interdisciplinary Laboratory of Clinical Neurosciences, Universidade Federal

*Corresponding author: Sintia Iole Belangero, PhD

Disciplina de Genética/ Departamento de Morfologia e Genética UNIFESP/EPM Rua Botucatu, 740, Ed. Leitão da Cunha, 1º andar, 04023-900, São Paulo, Brazil Phone: +5511-5576-4260 Fax: +5511-5579-8378

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E-mail: [email protected]

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ACCEPTED MANUSCRIPT ABSTRACT Telomeres are repetitive DNA sequences at the ends of chromatids that shorten following each cell replication. Once telomeres reach a critical length, DNA defense mechanisms can direct cells to either a state of arrest (senescence) or apoptosis. Stress induced by adversity is a probable cause of accelerated telomere shortening from an

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early age. However, few studies have examined the association between stress and telomere length in children, and it remains unclear whether young individuals may show signs of cellular aging early in life. Our aim was to examine whether adversity in childhood is associated with shortening of telomere length. We conducted a systematic

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review of studies that investigated the association between stress and telomere length in children from 3 to 15 years of age. Eleven studies met our selection criteria. We concluded that adversity in childhood (such as violence, low socioeconomic status,

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maternal depression, family disruption, and institutionalization) have an impact on telomere length. This suggests that exposed individuals show signs of accelerated erosion of telomeric ends from an early age. We discuss whether telomere shortening is related to negative health outcomes later in life or could be a biomarker predicting health outcomes. We believe that further large-scale longitudinal studies that repeatedly

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monitor telomere length are very important for providing a better assessment of telomere trajectory in psychologically stressed children. This will verify the extent to which adversity impacts upon the biological development of cell aging in childhood.

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Keywords: Telomere length; Early life stress; Adverse events; Children; Systematic review.

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ACCEPTED MANUSCRIPT 1. Introduction Exposure to repeated or prolonged stress is associated with telomere shortening and the development of age-related diseases (Quinlan et al., 2014), such as diabetes mellitus (Salpea et al., 2010), cardiopathology (Haycock et al., 2014; Willeit et al., 2010), dementia (Honig et al., 2012), and osteoarthritis (Kuszel et al., 2015).

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Accelerated aging and senescence have also become major concerns in psychiatry (Blaze et al., 2015), with shorter telomeres found in individuals with bipolar disorder (Lima et al., 2015), schizophrenia (Kao et al., 2008), major depression (Cai et al., 2015;

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Verhoeven et al., 2014), and post-traumatic stress disorder (Lohr et al., 2015).

Telomeres are DNA-protein complexes that cap the ends of eukaryotic chromosomes (Lindqvist et al., 2015) binding to G-rich DNA clusters, forming loops

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and acting as protective structures at chromosome termini (Koliada et al., 2015). A word derived from Greek — telos (end) and meros (part) (Boukamp and Mirancea, 2007; McClintock, 1939) — telomeres are essential for cell stability, preventing chromosomes from degenerating and from fusing with one another (Houben et al., 2008). In humans, telomeres are composed of the repeating hexanucleotide sequence

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TTAGGG and require a minimal length to maintain stability (Blackburn, 1990). In somatic cells, telomere shortening occurs after each chromosome replication. This incomplete replication of telomeric ends (Xu and Goldkorn, 2016) is termed the “End Replication Problem”. Other damage-causing mechanisms that contribute to

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telomere shortening include nuclease action, chemical damage (such as oxidative stress), DNA replication stress, epigenetic regulation, and genetic factors (Blackburn et

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al., 2015). Once telomeres reach a critical length, cellular defense mechanisms activate tumor suppressor genes, resulting in cells entering a state of arrest (senescence) or apoptosis (death) (Zakian, 2012). These biological responses are triggered to protect DNA coding regions from degradation, and to prevent DNA-damaged cells from proliferating (Zakian, 2012). As chronic or excessive activation of the stress response may result in telomere shortening, it is important to understand the impact of psychological stress on cell aging (Grippo and Johnson, 2009). One of the first studies to examine stress and telomere 3

ACCEPTED MANUSCRIPT length was conducted by Epel et al. (2004), who found that higher levels of perceived stress in healthy women positively correlated with shorter telomere length (Epel et al., 2004). Some studies have proposed that individuals exposed to child maltreatment or abuse would show accelerated shortening of telomeres in peripheral cells (Price et al.,

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2013; Shalev, 2012). Also, some studies suggest that stress and glucocorticoid exposure hasten telomere shortening and ageing (Haussmann et al., 2012). O’Donovan et al. (2011) and Tyrka et al. (2010) found telomere shortening in adults exposed to early-life adversity compared with healthy adults who were not. In contrast, Glass et al. (2010)

similar groups (Glass et al., 2010; Kuffer et al., 2016).

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and Küffer et al. (2016) did not find any difference in telomere length when comparing

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Childhood adversity is a consistent risk factor for many psychiatric disorders (Benjet et al., 2010) and neurobiological alterations (Heim et al., 2010). The aim of our study was to examine the association between telomere length in children/adolescents and stressful events caused by early-life adversities, such as abuse, maltreatment, family disruption, institutionalization, and low socioeconomic status. We aimed to search the literature from the perspective of childhood telomere length to investigate whether

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telomere shortening is related to early-life stress as opposed to address the relationship between retroactive report of childhood adversities and telomere length in adults. Published studies correlating exposure to adverse events during childhood and

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telomere length in adults are retrospective. This self-assessment is biased due to memory bias and confounding factors like age. Evaluation of telomere length in adults,

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many years after exposure, may make it difficult to separate out the effects of other subsequent factors, such as smoking and alcohol/drug abuse, other difficulties, and trauma during life. Our review aimed to reveal whether telomere shortening is observed in children during, or shortly after, exposure to stress. This strategy addresses the limitations of retrospective reports of childhood adversity and telomere length in adults (Naess and Kirkengen, 2015; Price et al., 2013; Quinlan et al., 2014; Shalev et al., 2013).

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ACCEPTED MANUSCRIPT We have identified, assessed, and summarized the literature to: (a) evaluate the cross-sectional association between stress and telomere length; (b) investigate longitudinal associations between stress and telomere length; and (c) investigate casecontrol studies to determine whether telomere length in case groups is more greatly affected. To our knowledge, there is no existing published review compiling the

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findings of studies in which telomere length was measured only in children.

2. Material and methods

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2.1. Systematic review

Articles included in the present systematic review were retrieved from PubMed

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(www.ncbi.nlm.nih.gov/pubmed), the Cochrane Library (www.cochranelibrary.com), the American Psychological Association – PsycINFO database (www.apa.org), and Lilacs (lilacs.bvsalud.org/) with a publication date prior to 30 July 2016. The MeSH terms used were “telomere” AND “children stress,” “childhood stress,” “child psychiatry,” “child sex abuse,” “child abuse,” “maltreatment”, “early adversity”,

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“children socioeconomic status” and “social deprivation”. 2.2. Inclusion eligibility

We included studies of children exposed to adversity. Child stress was assessed

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using gold standard, validated instruments (see section 3.3.). Articles were selected using the following inclusion criteria: a) publication date prior to July 30, 2016; b) written in English; c) association of life adversities and telomere length examined,

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having children as participants. 2.3. Exclusion criteria

This study was based exclusively on studies that examined the effects of

psychological stress on telomere length in children aged 6–15 years old. Therefore, retrospective studies with adults reporting adversity in childhood were not eligible. Studies of children with clinical medical conditions were excluded to avoid potential cofounding factors. 5

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3. Results 3.1. Literature search Eligible studies were identified through a systematic search in PubMed,

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Cochrane, PsycINFO, and Lilacs using specific MeSH terms. The search process is shown in Figure 1. Each article title was initially assessed, followed by the abstract, and all duplicates removed. We found 109 articles following this initial search that were further evaluated by their abstracts. Sixty-seven studies were excluded using the

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following exclusion criteria: animal studies (N = 3), studies that did not perform telomere analysis (N = 11), studies involving external agents such as chemicals and radiation (N = 13), magazine articles, interviews, and excerpts from books (N = 5),

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protocol reviews (N = 12), and clinical conditions (N = 23). The resulting 42 shortlisted articles were further evaluated, resulting in the exclusion of an additional 31 studies. These studies were excluded either because adults were recruited as subjects (N = 30) or because only the abstract of the study was available (N = 1). Eleven published articles

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were eligible for further analysis.

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ACCEPTED MANUSCRIPT Fig. 1. Flow diagram of the systematic review.

3.2. Summary of included studies The 11 studies were grouped based on the research method used into one of the

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study. A brief description of each study is provided in Table 1.

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following three categories: cross-sectional study, case-control study, or longitudinal

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Summary of the 11 studies examined.

P value

Outcome

Crosssectional study

Real time PCR

P = 0.004; standardized β = −0.33

Stress reactivity associated with telomere shortening

Crosssectional study

Real time PCR

P = 0.02; b = -0.49

Socioeconomic status associated with telomere shortening

Buccal

Crosssectional study

Real time PCR

P < 0.05; X2 regression = 6.20

Telomere shortening related to duration of exposure

Saliva

Crosssectional study

Real time PCR

P < 0.05; adjusted OR = 3.43; 95 % CI = 1.22, 9.62

Adversity associated with telomere shortening

Buccal

Crosssectional study

Real time PCR

P = 0.0053; β = 20.0086

Adversity associated with telomere shortening

Ethnicity

Age (years)

Gender

Sample type

Kroenke et al. 2011

78

Multiple ethnic groups

5–6

Male & female

Buccal

Needham et al. 2012

70

African American and Caucasian

7 – 13

Male & female

109

Romanian and other ethnicities

6 – 10

Male & female

Theall et al. 2013

99

African American

4 – 14

Drury et al. 2014ª

80

African American (91%)

5 – 15

Blood

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Male & female

Male & female

Study method

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N

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Telomere analysis

Reference

Drury et al. 2012

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Table 1

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200

Latino

3–5

Male & female

Asok et al. 2013

51 (cases) and 38 (controls)

Multiple ethnic groups

3–6

Male & female

Mitchell et al. 2014

20 (cases) and 20 (controls)

African American

9

Male

Gotlib et al. 2014

50 (cases) and 47 (controls)

Multiple ethnic groups

10 – 14

Shalev et al. 2013

236

Caucasian

Baseline 5 Follow-up at 10

Real time PCR

P < 0.01; β = -0.87

Telomere shortening associated with high levels of testosterone

Blood

Crosssectional study

Real time PCR

P = 0.01; β = -363.99; 95 % CI = 651.24, 764.74

Exposure to maternal clinical depression associated with telomere shortening

Buccal

Case-control study

Real Time PCR

P < 0.05; F (1,83) = 4.37

Telomere shortening in the case group

Saliva

Case-control study

Real time PCR

P = 0.02; b = -0.19

Adversity associated with telomere shortening

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Wojcicki et al. 2015

Buccal

Crosssectional study

Saliva

Case-control study

Real Time PCR

P = 0.001; t (95) = 3.582

Telomere shortening in the case group (daughters of depressed mothers)

Buccal

Longitudinal study

Real Time PCR

P = 0.015; b = 0.052

Adversity associated with telomere shortening

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Female

Male & female

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5 – 15

Male & female

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77

African American (91%)

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Drury et al. 2014b

Colors indicate different research methods. OR: odds ratio; CI: confidence interval; P: P value. 9

ACCEPTED MANUSCRIPT 3.3. Descriptions of study methods and main findings 3.3.1. Cross-sectional studies Kroenke et al. (2011) found correlations between autonomic (heart rate, respiratory sinus arrhythmia, and pre-ejection period) reactivity and adrenocortical

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(salivary cortisol) reactivity and telomere length (TL). Assessments to reveal internalizing and externalizing symptoms (the MacArthur Health and Behavior Questionnaire) and the children’s recent behaviors (Likert Scale) were completed by parental caregivers and school teachers. Children were invited to respond to the Berkeley Puppet Interview (BPI). A reactivity protocol was designed to induce

associated

with

shorter

TL

in

buccal

cells.

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autonomic responses. When combined, autonomic and adrenocortical reactivity were This

finding

indicated

that

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psychophysiological processes may have an effect on TL, and highlighted the use of buccal cells as a potential marker for early biological aging (Kroenke et al., 2011). Needham et al. (2012) found an association between parental socioeconomic status and TL in children. Socioeconomic status (SES) was determined by parental education level and household income. The authors used fruit and vegetable

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consumption per day, body mass index, and the frequency of physical exercise (Physical Activity Questionnaire for Older Children) as mediating factors between SES and TL, based on evidence from the literature. Children living in low-income households had lower T/S ratios (relative ratio of telomere repeat region and single-

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copy gene) than those living in high-income households. Also, the authors found that children whose parents never attended college had shorter telomeres compared with

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children with at least one college-educated parent (Needham et al., 2012). No correlation between T/S ratio and the proposed mediators was found. Theall et al. (2013) evaluated the impact of adversity at the community level,

rather than at the level of single households and families. They found decreased TL in children living in neighborhoods with high levels of adversity and disorders than in children living in less disadvantaged environments. Neighborhood adversity was defined as exposure to social deprivation with a percentage of residents below the poverty line (US standards). Neighborhood disorder (based on caregiver evaluation) 10

ACCEPTED MANUSCRIPT was indicated by the presence of litter, garbage, graffiti, broken steps, and abandoned vehicles and houses (Theall et al., 2013). Drury et al. performed three cross-sectional studies included in our review (Drury et al., 2014a; Drury et al., 2014b; Drury et al., 2012). The 2012 study is the only study we found that enrolled an exclusive sample of institutionalized children

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(Bucharest Early Intervention Project, Romania). Detailed records of these children’s institutional histories were described in detail elsewhere (Nelson et al., 2007; Zeanah et al., 2009). Their results confirmed the hypothesis that there is an association between TL and duration of institutional care. The children who were in institutional care for

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considerably longer periods had significantly shorter relative telomere lengths.

The other two studies by Drury et al. (2014) evaluated the same cohort of

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children from the New Orleans area. In one study, they examined the effects of interpersonal violence and family disruption on TL (Drury et al., 2014a). Life events, such as life threats to the child or someone close, as well as suicide or incarceration of a family member, were provided by each child’s parental caregivers. Parents also completed the Preschool Age Psychiatric Assessment. The authors concluded that

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cumulative exposure to witnessing interpersonal violence within the family, as well as family disruption (incarceration or suicide), was correlated with shorter TL. The second study by (Drury et al., 2014b) evaluated the association between telomere length and testosterone reactivity. To induce stress, children performed the

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Trier Social Stress Test, and saliva samples were collected at different times for testosterone measurement. The authors found that higher testosterone levels, and slower

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recovery and reactivity following social stressor exposure, were associated with shorter TL in buccal cells. This demonstrated that gonadal maturation may be a sensitive developmental biomarker for accelerated-aging in youth. Wojcicki et al. (2015) investigated the associations between maternal

depression and child behavioral issues and TL. An ethnically homogenous sample consisting of 200 Latino children was recruited from two hospitals. Data on pre- and post-maternal depressive symptoms were collected prenatally, 4–6 weeks after the child’s birth, and annually up to the 5-year follow-up. Three instruments were selected 11

ACCEPTED MANUSCRIPT to assess maternal depression: The Edinburg Postpartum Depression Scale, the Center for

Epidemiologic

Studies

Depression

Scale,

and

the

MINI

International

Neuropsychiatric Interview (version 5.0). Oppositional defiant disorder, exposure to maternal clinical depression, shorter maternal TL, and younger paternal age at time of birth were associated with shorter TL in children at different ages (Wojcicki et al.,

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2015). Although this is a longitudinal study, TL analysis was cross-sectional. 3.3.2. Case-control studies

Asok et al. (2013) examined whether there was an association between paternal responsiveness and telomere length in a cohort of high-risk children compared with

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controls. Using information from the child welfare system, high-risk children were identified based on their risk of maltreatment. The control group consisted of children

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with lower risks of maltreatment recruited from local childcare centers. Parental responsiveness was assessed using a semi-structured interactional task. They found that low parental responsiveness in high-risk children correlated with significantly shorter telomeres, compared with low-risk children. This finding remained after controlling for different variables such as household income, birth weight, gender, and minority status

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(Asok et al., 2013).

Mitchell et al. (2014) recruited African-American boys living in disadvantaged environments, with low economic status, family instability, poor parental quality, and maternal depression. The control group was contained children living in affluent, stable

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families, unexposed to harsh parenting or maternal depression. The instruments used were the Conflict Tactics Scale and a short version of the Composite International

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Diagnostic Interview, and were responded to by the caregivers. The authors found that shortened TL was associated with exposure to disadvantaged environments, such as low income, low maternal education, unstable family structure, and harsh parenting. Furthermore, these effects were moderated by genetic variants in the serotonergic and dopaminergic pathways. The authors investigated whether there was evidence of an association between a genetic score, derived from the presence of risk alleles in candidate genes, and telomere length. They found that subjects with the highest genetic sensitivity scores had the shortest TL when exposed to disadvantaged social environments (Mitchell et al., 2014). 12

ACCEPTED MANUSCRIPT Gotlib et al. (2014) performed a case-control study with 97 healthy girls. The high-risk group included girls (50) whose mothers had recurrent episodes of depression as were diagnosed using the Structured Clinical Interview for DSM-IV Axis I Disorders. The control group (47) included girls whose mothers did not report a previous or existing Axis I major mental disorder. All children who participated in the

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study had no diagnosis of a mental disorder according to the Kiddie-SADS Interview. The girls also completed the 10-item version of the Children’s Depression Inventory and had pubertal status assessed via Tanner Staging (I–V). Children underwent stressinducing activities and cortisol levels were measured. The authors found an association

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between shorter TL in the daughters of depressed mothers compared with that in the daughters of depression-free mothers. There was also an association between shorter TL

et al., 2014). 3.3.3. Longitudinal studies

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and increased cortisol reactivity to stress in the daughters of depressed mothers (Gotlib

Shalev et al. (2013) evaluated 236 British children from 118 different families that had at least one monozygotic twin. Buccal samples for DNA extraction were

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collected at 5 and 10 years of age. The study assessed three types of violence: witnessing different forms of domestic violence between parents or caregivers (as determined using the Conflict Tactics Scale), bullying victimization through narrative recordings with the mothers, and psychical maltreatment by an adult. The authors found

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that children who experienced two or more kinds of exposure to violence had significantly greater telomere erosion from the age of 5 to 10 compared with that in

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children who had fewer exposures to violence (Shalev et al., 2013). 3.4. Assessment of telomere length All 11 journal articles reviewed used quantitative PCR to measure telomere

length. With the exception of one article (Drury et al., 2012), all studies cited at least one of Cawthon’s papers in their references (Cawthon, 2002,2009).

4. Discussion 13

ACCEPTED MANUSCRIPT All studies included in this review showed a significant relationship between early-life adversity and childhood telomere length, however no causal relationship can be claimed. It is important to highlight that life adversity is a broad concept that includes a range of different negative experiences, such as family and community poverty, exposure to household violence, family disruption, social deprivation,

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institutionalization, and maternal depression. These adversities may be intertwined, as children can be exposed to more than one kind. We evaluated how each of these adversities is described in our paper selection as potential contributors to the acceleration of telomere shortening in children.

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It has been suggested that poverty negatively influences child health and predicts unfavorable adult health behaviors (Chen, 2004). Socioeconomic status (SES) is a

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widely-considered factor for telomere analysis in high-risk children. Our review concluded that low SES accelerates cellular aging in children, with signs of rapid telomere erosion in the poorest children assessed (Asok et al., 2013; Drury et al., 2014a; Mitchell et al., 2014; Needham et al., 2012). Additionally, four studies found that low levels of parental education (a marker of SES) are associated with shorter TL in children (Drury et al., 2014a; Mitchell et al., 2014; Needham et al., 2012; Theall et al., 2013). It

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is also of relevance that adversity caused by low SES can impact not only the family/household, but also at the community level. Theall et al. (2013) concluded that neighborhood disorders and adversity also negatively affect TL in children.

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Poor nutrition is also associated with low SES (Caprio et al., 2008) and malnutrition in children may result in physical growth deficits (Johnson et al., 2010).

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Predominant consumption of high calorie foods (usually cheaper and more easily accessed in low-income households) over a diet of nutrient-rich products (e.g. fruit and vegetables) may speed telomere decline (Shiels et al., 2011). Needham et al. (2012) were the only authors in this review to consider fruit and vegetable consumption as a mediator of TL, although no evidence of a correlation was found. Additionally, Needham et al. (2012) also investigated the association between frequency of physical activity (a mediator of TL) and telomere shortening, again with no association detected. However, Cherkas et al. (2008) found that sedentarism may be associated with shorter TL (Cherkas et al., 2008). Further TL studies in children should 14

ACCEPTED MANUSCRIPT include a detailed assessment of nutritional and physical activity habits, as high-quality nutrition and engagement in physical exercise may potentially act as antiaging factors. Drury et al. (2012) conducted the only study in this review that examined the effects of institutionalization on TL. The authors concluded that the longer children were exposed to institutional care, the greater the reduction of TL (Drury et al., 2012).

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Children are more vulnerable in institutional facilities where attention to their specific needs, proper nutrition, and high-quality care are generally lacking (Drury et al., 2012). This puts into perspective the essentialness of parental responsiveness in moderating early-life stress in children. This involves responding timely and equitably to the child’s

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needs, signals, expressions, and behavior, in an attached and non-invasive manner (Asok et al., 2013). Asok et al. (2013) concluded that unresponsive parenting is

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associated with shorter TL in high-risk children. This is consistent with Drury et al.’s (2012) results from a population of high-risk institutionalized children and their study of short TL in children who experienced disruption caused by incarceration or suicide of a family member (Drury et al., 2014a).

Telomere shortening was also identified in children subjected to violence and

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maltreatment. According to Shalev et al (2013) the frequency of violent episodes that a child is exposed to is indicative of higher telomere attrition (Shalev et al., 2013). The inversely proportional relationship between frequency of trauma and TL attest to the unfavorable effects of cumulative stress (Shalev et al., 2013). Witnessing interpersonal

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violence in the domestic environment and harsh psychological and physical behavior from a parent are positively associated with telomere shortening in children (Drury et

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al., 2012; Mitchell et al., 2014). No study has yet assessed TL in children living in war zones, refugee camps, or urban centers exposed to high rates of crime and violence. Studies targeting children in such conflicted environments are important for elucidating the effect of an unsafe environment on cellular aging. It should be noted that the results in this review cannot be generalized globally. Nine articles presented studies with children in the US, one in the United Kingdom (Shalev et al., 2013), and only one from a developing country – Romania (Drury et al., 2012). New population data from developing and newly industrialized countries – where levels of violence, malnutrition, and socio-economic and educational attainment 15

ACCEPTED MANUSCRIPT disparities may be higher than in the developed countries – may identify other factors associated with stress-related telomere stability. Maternal depression is an additional difficulty for children (Mitchell et al., 2014). Evidence suggests that maternal depression may impose environmental adversity on children (Goodman and Gotlib, 1999). Children whose mothers have major

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depressive disorder (MDD) have increased levels of glucocorticoids in response to stressors compared with their peers with parents with no MDD (Azar et al., 2007; Lupien et al., 2011). In our review, three studies (Gotlib et al., 2014; Mitchell et al., 2014; Wojcicki et al., 2015) found a relationship between telomere shortening in

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children and mothers with clinical depression. In Wojcicki et al. (2015), the sample was homogenous in regard to SES and ethnic background, which strengthens the association

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of TL in children with maternal depression. Even if children exposed to maternal depression manifest no symptoms of MDD, having a mother with a history of depression or recurrent depressive episodes increases rates of telomere attrition in early age and greater cortisol reactivity, leaving an imprint of aging acceleration in cells (Gotlib et al., 2014).

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Positive associations between high cortisol reactivity to stress and shorter TL in children were found in two articles in our selection: Kroenke et al. (2011) and Gotlib et al. (2014). Kroenke et al. (2011) stated that these findings of higher levels of cortisol in children were consistent with studies that found an association between urinary stress

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hormones and shorter telomeres in adults (Kroenke et al., 2011). Drury et al. (2014b) found that children with shortened telomeres have higher testosterone peaks as well as a

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slower testosterone recoveries in response to standardized acute stressors (Drury et al., 2014b). Testosterone may be released in response to stressful situations. Children with increased sensitivity to stress-induced situations have higher levels of testosterone and shorter telomeres. These two distinct biological factors that are affected by stress may share common mechanisms that underlie biological aging (Drury et al., 2014b). One inconsistency in our study is the role of gender in the telomere response to stress. Studies have reported conflicting data on this issue. Mitchell et al. (2014) raised the question of whether boys are more sensitive to stress than girls. Asok et al. (2013) posed the question whether distress in boys is more erosive to telomeres because of an 16

ACCEPTED MANUSCRIPT increased exposure to adversity. In contrast, Drury et al. (2014a) found greater impact of cumulative exposure on TL in girls, while no correlation was found within boys. As mentioned in the introduction of this article, retroactively reported childhood adversity showed no correlation to TL in adults in some studies, contradicting the occurrence of shortened TL in stressed children. These findings may be explained by

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memory recall bias or point to the possibility of a generative process over time where TL is restored in healthy individuals. It may even suggest that short TL may constitute a congenital factor increasing vulnerability to stress. Another possibility according to Mitchell and collaborators (2014) is that there are genetically encoded differential

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sensitivity to the environment so that more sensitive individuals have longer TL in advantaged environments and shorter TL in disadvantaged environments, when

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compared with less genetically sensitive individuals (Boyce and Ellis, 2005). There are aspects of telomere dynamics both in adults and in children that remain unclear. One particular characteristic of TL biology in children, for example, is that it seems that the greatest acceleration of telomeric loss occurs in the first 4 or 5 years of a person’s life (Frenck et al., 1998; Zeichner et al., 1999). Conversely, several

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longitudinal studies have reported that some individuals may show elongation of telomeric DNA after baseline measurement (Ehrlenbach et al., 2009; Nordfjall et al., 2009). In the only longitudinal study in our review, the authors found that some children showed telomere lengthening in the follow-up assessment (Shalev et al., 2013).

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Telomeric gain may reflect complexities in telomere dynamics as an increasing number of studies have reported that linear telomere erosion is not inevitable throughout

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the life span (Ehrlenbach et al., 2009; Farzaneh-Far et al., 2010; Shalev, 2012). Telomeres appear to be oscillatory structures, varying in size across periods of time, although tending towards a pattern of progressive shortening (Epel, 2012; Svenson et al., 2011; Verhoeven et al., 2014). This should enable further debate about whether lifestyle changes and stress reduction strategies may circumstantially replenish telomeric DNA eroded by stress and unhealthy habits; a hypothesis tested with positive outcomes by three studies (Conklin et al., 2015; Ornish et al., 2013; Sjogren et al., 2014). This is significant because it may point to the eventual benefits of early intervention. We suggest that more longitudinal studies with multiple telomere length assessments are 17

ACCEPTED MANUSCRIPT needed to better investigate telomere trajectory in children exposed to adversity. Longitudinal studies are essential for measuring the acceleration of telomere shortening in stressed children and to determine to what extent telomeres respond if exposure to adversity reduces. Even if ultimately telomeres must decline, we believe, like Shalev (2012), that improvements in children’s environmental conditions, reduction of

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stressors, and better health behaviors, may help slow cellular aging and minimize negative health outcomes (Shalev, 2012).

This systematic review has summarized the association between stress and telomere length in children, which was positively verified by the 11 eligible articles.

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There are variable sources of adversity reported in our analysis, all potential factors for telomere attrition. Despite the limited number of published studies in the literature, we

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believe there is a significant body of evidence to confirm that acceleration of telomeric loss is already observable in children shortly after exposure to adversity. Individuals with shortened telomeres are more likely to manifest age-related diseases across the lifespan. This raises concern because adversity may set parameters of health deterioration from an early age, even if the clinical signs of disease onset are only detectable many years after. High-risk children must be protected from stress and

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stressful environments. Caregivers, community members, and mental health professionals have a fundamental role in this. We recommend large scale longitudinal studies following TL in children from infancy to adulthood, with multiple assessments of TL, genetics/epigenetics, and life events. These should shed light on the complex

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interplay between environmental factors, cellular aging, and disease progression. This is of specific importance for the design of targeted and effective preventions of cellular

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aging and negative health outcomes.

ROLE OF THE FUNDING SOURCE This work was supported by a research grant from the Fundação de Amparo à Pesquisa do Estado de São Paulo (Vidi grant: FAPESP 2014/12559-5).

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ACCEPTED MANUSCRIPT CONFLICT OF INTEREST None.

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ACKNOWLEDGMENT This work was supported by a research grant from the Fundação de Amparo à Pesquisa

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do Estado de São Paulo (Vidi grant: FAPESP 2014/12559-5).

REFERENCES

M AN U

Asok A, Bernard K, Roth TL, Rosen JB, Dozier M. Parental Responsiveness Moderates the Association Between Early-life Stress and Reduced Telomere Length. Development and psychopathology. 2013;25:577-85.

Azar R, Paquette D, Zoccolillo M, Baltzer F, Tremblay RE. The association of major depression, conduct disorder, and maternal overcontrol with a failure to show a cortisol

2007;62:573-9.

TE D

buffered response in 4-month-old infants of teenage mothers. Biol Psychiatry.

Benjet C, Borges G, Medina-Mora ME. Chronic childhood adversity and onset of psychopathology during three life stages: childhood, adolescence and adulthood. J

EP

Psychiatr Res. 2010;44:732-40.

Blackburn EH. Telomeres: structure and synthesis. J Biol Chem. 1990;265:5919-21.

AC C

Blackburn EH, Epel ES, Lin J. Human telomere biology: A contributory and interactive factor in aging, disease risks, and protection. Science. 2015;350:1193-8. Blaze J, Asok A, Roth TL. The long-term impact of adverse caregiving environments on epigenetic modifications and telomeres. Front Behav Neurosci. 2015;9. Boukamp P, Mirancea N. Telomeres rather than telomerase a key target for anti-cancer therapy? Experimental Dermatology. 2007;16:71-9. Boyce WT, Ellis BJ. Biological sensitivity to context: I. An evolutionary-developmental theory of the origins and functions of stress reactivity. Dev Psychopathol. 2005;17:271301. 19

ACCEPTED MANUSCRIPT Cai N, Chang S, Li Y, Li Q, Hu J, Liang J, et al. Molecular Signatures of Major Depression. Current Biology. 2015;25:1146-56. Caprio S, Daniels SR, Drewnowski A, Kaufman FR, Palinkas LA, Rosenbloom AL, et al. Influence of Race, Ethnicity, and Culture on Childhood Obesity: Implications for Prevention and Treatment: A consensus statement of Shaping America's Health and the

RI PT

Obesity Society. Diabetes Care. 2008;31:2211-21. Cawthon RM. Telomere measurement by quantitative PCR. Nucleic Acids Research. 2002;30:e47-e.

Cawthon RM. Telomere length measurement by a novel monochrome multiplex

SC

quantitative PCR method. Nucleic Acids Research. 2009;37:e21-e.

Chen E. Why Socioeconomic Status Affects the Health of Children: A Psychosocial Perspective. Current Directions in Psychological Science. 2004;13:112-5.

M AN U

Cherkas LF, Hunkin JL, Kato BS, Richards JB, Gardner JP, Surdulescu GL, et al. The association between physical activity in leisure time and leukocyte telomere length. Arch Intern Med. 2008;168:154-8.

Conklin Q, King B, Zanesco A, Pokorny J, Hamidi A, Lin J, et al. Telomere lengthening

after

three

weeks

of

an

intensive

insight

meditation

retreat.

TE D

Psychoneuroendocrinology. 2015;61:26-7.

Drury SS, Mabile E, Brett ZH, Esteves K, Jones E, Shirtcliff EA, et al. The Association of Telomere Length With Family Violence and Disruption. Pediatrics. 2014a;134:e128e37.

EP

Drury SS, Shirtcliff EA, Shachet A, Phan J, Mabile E, Brett ZH, et al. Growing Up Or Growing Old? Cellular Aging Linked With Testosterone Reactivity To Stress In Youth. The American journal of the medical sciences. 2014b;348:92-100.

AC C

Drury SS, Theall K, Gleason MM, Smyke AT, De Vivo I, Wong JYY, et al. Telomere length and early severe social deprivation: linking early adversity and cellular aging. Molecular Psychiatry. 2012;17:719-27. Ehrlenbach S, Willeit P, Kiechl S, Willeit J, Reindl M, Schanda K, et al. Influences on the reduction of relative telomere length over 10 years in the population-based Bruneck Study: introduction of a well-controlled high-throughput assay. International Journal of Epidemiology. 2009;38:1725-34.

20

ACCEPTED MANUSCRIPT Epel E. How “Reversible” Is Telomeric Aging? Cancer Prevention Research. 2012;5:1163-8. Epel ES, Blackburn EH, Lin J, Dhabhar FS, Adler NE, Morrow JD, et al. Accelerated telomere shortening in response to life stress. Proceedings of the National Academy of Sciences of the United States of America. 2004;101:17312-5.

RI PT

Farzaneh-Far R, Lin J, Epel E, Lapham K, Blackburn E, Whooley MA. Telomere Length Trajectory and Its Determinants in Persons with Coronary Artery Disease: Longitudinal Findings from the Heart and Soul Study. PLoS ONE. 2010;5:e8612.

Frenck RW, Blackburn EH, Shannon KM. The rate of telomere sequence loss in human

United States of America. 1998;95:5607-10.

SC

leukocytes varies with age. Proceedings of the National Academy of Sciences of the

Glass D, Parts L, Knowles D, Aviv A, Spector TD. No Correlation Between Childhood

M AN U

Maltreatment and Telomere Length. Biological Psychiatry. 2010;68:e21-e2. Goodman SH, Gotlib IH. Risk for psychopathology in the children of depressed mothers: a developmental model for understanding mechanisms of transmission. Psychol Rev. 1999;106:458-90.

Gotlib IH, LeMoult J, Colich NL, Foland-Ross LC, Hallmayer J, Joormann J, et al.

TE D

Telomere length and cortisol reactivity in children of depressed mothers. Molecular Psychiatry. 2014;20:615-20.

Grippo AJ, Johnson AK. Stress, depression and cardiovascular dysregulation: a review of neurobiological mechanisms and the integration of research from preclinical disease

EP

models. Stress. 2009;12:1-21.

Haussmann MF, Longenecker AS, Marchetto NM, Juliano SA, Bowden RM. Embryonic exposure to corticosterone modifies the juvenile stress response, oxidative

AC C

stress and telomere length. Proc Biol Sci. 2012;279:1447-56. Haycock PC, Heydon EE, Kaptoge S, Butterworth AS, Thompson A, Willeit P. Leucocyte telomere length and risk of cardiovascular disease: systematic review and meta-analysis. Bmj. 2014;8. Heim C, Shugart M, Craighead WE, Nemeroff CB. Neurobiological and psychiatric consequences of child abuse and neglect. Dev Psychobiol. 2010;52:671-90.

21

ACCEPTED MANUSCRIPT Honig LS, Kang MS, Schupf N, Lee JH, Mayeux R. Association of Shorter Leukocyte Telomere Repeat Length with Dementia and Mortality. Archives of neurology. 2012;69:1332-9. Houben JMJ, Moonen HJJ, van Schooten FJ, Hageman GJ. Telomere length assessment: Biomarker of chronic oxidative stress? Free Radical Biology and Medicine.

RI PT

2008;44:235-46. Johnson DE, Guthrie D, Smyke AT, Koga SF, Fox NA, Zeanah CH, et al. Growth and associations between auxology, caregiving environment, and cognition in socially deprived Romanian children randomized to foster vs ongoing institutional care. Arch

SC

Pediatr Adolesc Med. 2010;164:507-16.

Kao HT, Cawthon RM, Delisi LE, Bertisch HC, Ji F, Gordon D, et al. Rapid telomere in

schizophrenia:

10.1038/sj.mp.4002105.; 2008.

Mol

Psychiatry.

2008

Feb;13(2):118-9.

doi:

M AN U

erosion

Koliada AK, Krasnenkov DS, Vaiserman AM. Telomeric aging: mitotic clock or stress indicator? Frontiers in Genetics. 2015;6:82.

Kroenke CH, Epel E, Adler N, Bush NR, Obradović J, Lin J, et al. Autonomic and adrenocortical reactivity and buccal cell telomere length in kindergarten children.

TE D

Psychosomatic medicine. 2011;73:533-40.

Kuffer AL, O'Donovan A, Burri A, Maercker A. Posttraumatic Stress Disorder, Adverse Childhood Events, and Buccal Cell Telomere Length in Elderly Swiss Former Indentured Child Laborers. Front Psychiatry. 2016;7.

EP

Kuszel L, Trzeciak T, Richter M, Czarny-Ratajczak M. Osteoarthritis and telomere shortening. Journal of Applied Genetics. 2015;56:169-76. Lima IM, Barros A, Rosa DV, Albuquerque M, Malloy-Diniz L, Neves FS, et al.

AC C

Analysis of telomere attrition in bipolar disorder. J Affect Disord. 2015;172:43-7. Lindqvist D, Epel ES, Mellon SH, Penninx BW, Revesz D, Verhoeven JE, et al. Psychiatric disorders and leukocyte telomere length: Underlying mechanisms linking mental illness with cellular aging. Neurosci Biobehav Rev. 2015;55:333-64. Lohr JB, Palmer BW, Eidt CA, Aailaboyina S, Mausbach BT, Wolkowitz OM, et al. Is Post-Traumatic Stress Disorder Associated with Premature Senescence? A Review of the Literature. The American Journal of Geriatric Psychiatry. 2015;23:709-25.

22

ACCEPTED MANUSCRIPT Lupien SJ, Parent S, Evans AC, Tremblay RE, Zelazo PD, Corbo V, et al. Larger amygdala but no change in hippocampal volume in 10-year-old children exposed to maternal depressive symptomatology since birth. Proc Natl Acad Sci U S A. 2011;108:14324-9. McClintock B. The Behavior in Successive Nuclear Divisions of a Chromosome

RI PT

Broken at Meiosis. Proceedings of the National Academy of Sciences of the United States of America. 1939;25:405-16.

Mitchell C, Hobcraft J, McLanahan SS, Siegel SR, Berg A, Brooks-Gunn J, et al. Social disadvantage, genetic sensitivity, and children’s telomere length. Proceedings of the

SC

National Academy of Sciences of the United States of America. 2014;111:5944-9.

Naess AB, Kirkengen AL. Is childhood stress associated with shorter telomeres? Tidsskr Nor Laegeforen. 2015;135:1356-60.

M AN U

Needham BL, Fernandez JR, Lin J, Epel ES, Blackburn EH. Socioeconomic status and cell aging in children. Social Science & Medicine. 2012;74:1948-51. Nelson CA, 3rd, Zeanah CH, Fox NA, Marshall PJ, Smyke AT, Guthrie D. Cognitive recovery in socially deprived young children: the Bucharest Early Intervention Project. Science. 2007;318:1937-40.

TE D

Nordfjall K, Svenson U, Norrback KF, Adolfsson R, Lenner P, Roos G. The individual blood cell telomere attrition rate is telomere length dependent. PLoS Genet. 2009;5:13. Ornish D, Lin J, Chan JM, Epel E, Kemp C, Weidner G, et al. Effect of comprehensive lifestyle changes on telomerase activity and telomere length in men with biopsy-proven

EP

low-risk prostate cancer: 5-year follow-up of a descriptive pilot study. Lancet Oncol. 2013;14:1112-20.

Price LH, Kao H-T, Burgers DE, Carpenter LL, Tyrka AR. Telomeres and Early-Life

AC C

Stress: An Overview. Biological Psychiatry. 2013;73:15-23. Quinlan J, Tu MT, Langlois ÉV, Kapoor M, Ziegler D, Fahmi H, et al. Protocol for a systematic review of the association between chronic stress during the life course and telomere length. Systematic Reviews. 2014;3:40-. Salpea KD, Talmud PJ, Cooper JA, Maubaret CG, Stephens JW, Abelak K, et al. Association of telomere length with type 2 diabetes, oxidative stress and UCP2 gene variation. Atherosclerosis. 2010;209:42-50.

23

ACCEPTED MANUSCRIPT Shalev I. Early life stress and telomere length: Investigating the connection and possible mechanisms: A critical survey of the evidence base, research methodology and basic biology. BioEssays : news and reviews in molecular, cellular and developmental biology. 2012;34:943-52. Shalev I, Moffitt TE, Sugden K, Williams B, Houts RM, Danese A, et al. Exposure to

a longitudinal study. Molecular Psychiatry. 2013;18:576-81.

RI PT

violence during childhood is associated with telomere erosion from 5 to 10 years of age:

Shiels PG, McGlynn LM, MacIntyre A, Johnson PCD, Batty GD, Burns H, et al. Accelerated Telomere Attrition Is Associated with Relative Household Income, Diet

SC

and Inflammation in the pSoBid Cohort. PLoS ONE. 2011;6:e22521.

Sjogren P, Fisher R, Kallings L, Svenson U, Roos G, Hellenius ML. Stand up for health--avoiding sedentary behaviour might lengthen your telomeres: secondary

M AN U

outcomes from a physical activity RCT in older people. Br J Sports Med. 2014;48:14079.

Svenson U, Nordfjäll K, Baird D, Roger L, Osterman P, Hellenius M-L, et al. Blood Cell Telomere Length Is a Dynamic Feature. PLoS ONE. 2011;6:e21485. Theall KP, Brett ZH, Shirtcliff EA, Dunn EC, Drury SS. Neighborhood disorder and

TE D

telomeres: Connecting children's exposure to community level stress and cellular response. Social Science & Medicine. 2013;85:50-8. Verhoeven JE, Revesz D, Epel ES, Lin J, Wolkowitz OM, Penninx BWJH. Major depressive disorder and accelerated cellular aging: results from a large psychiatric

EP

cohort study. Mol Psychiatry. 2014;19:895-901. Willeit P, Willeit J, Brandstatter A, Ehrlenbach S, Mayr A, Gasperi A, et al. Cellular aging reflected by leukocyte telomere length predicts advanced atherosclerosis and

AC C

cardiovascular disease risk. Arterioscler Thromb Vasc Biol. 2010;30:1649-56. Wojcicki JM, Heyman MB, Elwan D, Shiboski S, Lin J, Blackburn E, et al. Telomere length is associated with oppositional defiant behavior and maternal clinical depression in Latino preschool children. Translational Psychiatry. 2015;5:e581. Xu Y, Goldkorn A. Telomere and Telomerase Therapeutics in Cancer. Genes. 2016;7:22. Zakian VA. Telomeres: The beginnings and ends of eukaryotic chromosomes. Experimental Cell Research. 2012;318:1456-60. 24

ACCEPTED MANUSCRIPT Zeanah CH, Egger HL, Smyke AT, Nelson CA, Fox NA, Marshall PJ, et al. Institutional rearing and psychiatric disorders in Romanian preschool children. Am J Psychiatry. 2009;166:777-85. Zeichner SL, Palumbo P, Feng Y, Xiao X, Gee D, Sleasman J, et al. Rapid Telomere

AC C

EP

TE D

M AN U

SC

RI PT

Shortening in Children. Blood. 1999;93:2824-30.

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ACCEPTED MANUSCRIPT Highlights - Stress is associated with telomere shortening in children. - Early life adversity is associated with shorter telomere length in children.

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- Children exposed to adversity may show signs of cellular aging in early life.