Chronic and acute stress, gender, and serotonin transporter gene-environment interactions predicting depression symptoms in youth

Critical appraisal and systematic review of genes linked with cocaine addiction, depression and anxiety

Recent lifestyle changes have resulted in tremendous peer pressure and mental stress, and increased the incidences of chronic psychological disorders; like addiction, depression and anxiety (ADA). In this context, the stress-tolerance levels vary amongst individuals and genetic factors play prominent roles. Vulnerable individuals may often be drawn towards drug-addiction to combat stress. This systematic review critically appraises the relationship of various genetic factors linked with the incidences of ADA development. For coherence, we focused solely on cocaine as a substance of abuse in this study. Online scholarly databases were used to screen pertinent literature using apt keywords; and the final retrieval included 42 primary-research articles. The major conclusion drawn from this systematic analysis states that there are 51 genes linked with the development of ADA; and 3 (BDNF, PERIOD2 and SLC6A4) of them are common to all the three aspects of ADA. Further, inter-connectivity analyses of the 51 genes further endorsed the central presence of BDNF and SLC6A4 genes in the development of ADA disorders. The conclusions derived from this systematic study pave the way for future studies for the identification of diagnostic biomarkers and drug targets; and for the development of novel and effective therapeutic regimens against ADA.

Peer victimization, depression, and non-suicidal self-injury among Chinese adolescents: the moderating role of the 5-HTR2A gene rs6313 polymorphism

BACKGROUND

Peer victimization is a crucial risk predictor for adolescent non-suicidal self-injury (NSSI). However, adolescent NSSI reactions to peer victimization exhibit large individual differences. This study explored whether depression mediated the association between peer victimization and adolescent NSSI, and whether this mediating path was moderated by the 5-HTR2A gene rs6313 polymorphism.

METHODS

A total of 667 adolescents (Mean_age = 12.81, SD = 0.48) completed questionnaires regarding peer victimization, depression, and NSSI. Genomic DNA was extracted from saliva and buccal cells from each participant.

RESULTS

The results showed that the positive relation between peer victimization and adolescent NSSI was mediated by depression. Moreover, the triple interaction between peer victimization, rs6313 polymorphism, and gender on adolescent depression was significant. And the triple interaction between depression, rs6313 polymorphism, and gender on adolescent NSSI was also significant. Specifically, the risk effect of peer victimization on adolescent NSSI through increased depression was stronger for female adolescents with CC genotype than for female adolescents with CT or TT genotype, and male adolescents with CT or TT genotype. However, the indirect effect was nonsignificant for male adolescents with CC genotype.

CONCLUSIONS

These findings promote the etiological understanding of adolescent NSSI, highlighting the mediating and moderating effect between peer victimization and NSSI, and adding evidence supporting the relationship between the 5-HTR2A gene rs6313 polymorphism, depression and adolescent NSSI.

Studying the relationship between clinical features and mental health among late-onset myasthenia gravis patients

BACKGROUND

Mental disorders are common comorbidities among individuals with neurological diseases, and the prevalence of depressive and anxiety-related symptoms in newly referred patients at neurology outpatient clinics is high. There have been few studies on the mental health of patients with late-onset myasthenia gravis (MG).

AIM

To examine the relationship between clinical features and the mental health symptoms within late-onset MG patients.

METHODS

A total of 105 patients diagnosed with MG were recruited consecutively from a neuromuscular outpatient clinic between December 2020 and February 2021. Patients were classified into two groups: early-onset MG (age at onset < 50 years, n = 63) and late-onset MG (age at onset ≥ 50 years, n = 42). Social demographic data and information about marital status, education level, clinical symptoms, serum antibody levels, and therapies used were collected for all participants. Participants were also evaluated using the Myasthenia Gravis Composite scale, the Myasthenia Gravis Activities of Daily Living scale, the Myasthenia Gravis Quality of Life 15 (MG-QOL-15) questionnaire, the 17-item version of the Hamilton Depression Rating Scale (HAM-D) and the Hamilton Anxiety Rating Scale (HAM-A). The relationship between clinical features and mental health in late-onset MG patients was examined using multivariate logistic regression analyses.

RESULTS

Late-onset MG patients were more prone to dyspnea, had higher levels of serum anti-acetylcholine receptor antibodies, and higher total scores on the MG-QOL-15, HAM-D, and HAM-A questionnaires, than early-onset MG patients had (P < 0.05). Among those with late-onset MG, female patients had higher total HAM-D and HAM-A scores than male patients had (P < 0.05). High scores on the QOL-15 questionnaire were associated with higher incidences of anxiety and depression, and the association was found to be independent after adjusting for confounding risk factors. In the late-onset subgroup, the areas under the receiver operating characteristic curves for the MG-QOL-15 score-based diagnostic accuracy for anxiety and depression state were 0.816 (P = 0.001) and 0.983 (P < 0.001), respectively.

CONCLUSION

Higher MG-QOL-15 scores were a risk factor for anxiety and depression in late-onset MG, and women with late-onset MG were more likely to have anxiety and depression than men were.

Inflammatory cytokines and callosal white matter microstructure in adolescents

Adolescent depression is characterized by heightened inflammation and altered connectivity of fronto-cingulate-limbic tracts, including the genu of the corpus callosum (CCG) and the uncinate fasciculus (UF). No studies, however, have yet examined the association between inflammation, measured by peripheral levels of cytokines, and white matter connectivity of fronto-cingulate-limbic tracts in adolescents. Here, 56 depressed adolescents (32 females, 3 non-binary; 16.23 ± 1.28 years) and 19 controls (10 females; 15.72 ± 1.17 years) completed a diffusion-weighted MRI scan at 3 Tesla. We conducted deterministic tractography to segment bilateral corpus callosum (genu and splenium) and UF and computed mean fractional anisotropy (FA) in each tract. A subset of participants (43 depressed and 17 healthy controls) also provided dried blood spot samples from which we assayed interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-ɑ) using a Luminex multiplex array. Depressed participants did not differ from controls in FA of the corpus callosum or UF (all FDR-corrected ps > 0.056) but exhibited higher levels of inflammation than did controls (IL-6: β = 0.91, FDR-corrected p = 0.006; TNF-α: β = 0.76, FDR-corrected p = 0.006). Although diagnostic group did not moderate the associations between inflammatory cytokines and FA in the CCG and UF, across both groups, greater peripheral inflammation was associated with lower FA in the CCG (IL-6: β = -0.38; FDR-corrected p = 0.044; TNF-ɑ: β = -0.41, FDR-corrected p = 0.044). This study is the first to examine associations between peripheral inflammation and white matter microstructure of fronto-cingulate-limbic tracts in depressed and nondepressed adolescents. Future mechanistic studies are needed to confirm our findings; nevertheless, our results suggest that heightened inflammation is an important component of neurophenotypes that are relevant to adolescent depression.

Childhood Emotional Abuse and Depression Among Adolescents: Roles of Deviant Peer Affiliation and Gender

Adolescent depression is a significant concern around the world. There is a pressing need to explore risk factors for this disorder to develop better interventions. Based on an integration of attachment theory, Bronfenbrenner's ecological systems theory, and relational theory, the current study aimed to examine (a) whether childhood emotional abuse (CEA) would be significantly and positively related to adolescents' depression, (b) whether deviant peer affiliation would mediate the relation between CEA and depression, and (c) whether gender would moderate the direct and indirect relations between CEA and adolescent's depression via deviant peer affiliation. Participants were 961 Chinese adolescents (M_age = 15.21 years, SD = 1.57). They completed questionnaires regarding demographics, CEA, other types of childhood maltreatment (i.e., physical abuse, sexual abuse, physical neglect, and emotional neglect), deviant peer affiliation, and depression. Results showed that CEA was positively related to adolescent depression even after controlling for other types of childhood maltreatment, and this relation was mediated by deviant peer affiliation. Furthermore, moderated mediation analyses indicated that gender moderated the relation between CEA and deviant peer affiliation, with the relation being stronger for girls than for boys. However, gender did not moderate the relation between deviant peer affiliation and depression, as well as the direct relation between CEA and depression. Results highlight that interventions aimed at reducing CEA may protect adolescents, especially girls from the risks of deviant peer affiliation and depression.

Association of 5-HTTLPR/rs25531 with depressive symptoms in patients with coronary heart disease: A prospective study

BACKGROUND

5-HTTLPR/rs25531 is suspected to be involved in the pathogenesis of both coronary heart disease (CHD)¹ and depression. We aimed to investigate the role of 5-HTTLPR/rs25531 in the development of depressive symptoms among CHD patients in a longitudinal design.

METHODS

N = 265 participants with CHD diagnosis were included while hospitalized in a department of cardiology and genotyped for the 5-HTTLPR/rs25531. Depressive symptoms were measured using the Patient Health Questionnaire (PHQ-9)⁷ at baseline and after 6 and 12 months. Binary logistic regression models were used to analyze the association of 5-HTTLPR/rs25531 with the prevalence of depressive symptoms at each time point as well as with the incidence and persistence of depressive symptoms at follow-up.

RESULTS

"L_AL_A" genotype was associated with a higher prevalence of depressive symptoms 12 months after study inclusion. "L_AL_A" genotype was associated with a higher incidence of depressive symptoms 6 and 12 months after study inclusion. There was no association of 5-HTTLPR/rs25531 with the persistence of depressive symptoms.

LIMITATIONS

Inclusion criteria did not demand a particular cardiac event at baseline, which aggravated the interpretation of the time-specific results. The majority of the participants was of male gender which could cause bias. The present study only vaguely differentiated between ethnical groups which might cause bias regarding nationality-dependent allele distributions.

CONCLUSION

The present study suggests a time-dependent association of the "L_AL_A" genotype with depressive symptoms in CHD patients. 5-HTTLPR/rs25531 might be an important marker to detect risk groups for later onset depressive symptoms among CHD patients.

Polygenic Risk for Major Depression Interacts with Parental Criticism in Predicting Adolescent Depressive Symptom Development

Research has focused more and more on the interplay between genetics and environment in predicting different forms of psychopathology, including depressive symptoms. While the polygenic nature of depressive symptoms is increasingly recognized, only few studies have applied a polygenic approach in gene-by-environment interaction (G × E) studies. Furthermore, longitudinal G × E studies on developmental psychopathological properties of depression are scarce. Therefore, this 6-year longitudinal community study examined the interaction between genetic risk for major depression and a multi-informant longitudinal index of critical parenting in relation to depressive symptom development from early to late adolescence. The sample consisted of 327 Dutch adolescents of European descent (56% boys; M_age T₁ = 13.00, SD_age T₁ = 0.44). Polygenic risk for major depression was based on the Hyde et al. (Nature Genetics, 48, 1031–1036, 2016) meta-analysis and genetic sensitivity analyses were based on the 23andMe discovery dataset. Latent Growth Models suggested that polygenic risk score for major depression was associated with higher depressive symptoms across adolescence (significant main effect), particularly for those experiencing elevated levels of critical parenting (significant G × E). These findings highlight how polygenic risk for major depression in combination with a general environmental factor impacts depressive symptom development from early to late adolescence.

Gender Differences in Depression: Evidence From Genetics

Compared with men, female accounts for a larger proportion of patients with depression. Behavioral genetics researches find gender differences in genetic underpinnings of depression. We found that gender differences exist in heritability and the gene associated with depression after reviewing relevant research. Both genes and gene-environment interactions contribute to the risk of depression in a gender-specific manner. We detailed the relationships between serotonin transporter gene-linked promoter region (5-HTTLPR) and depression. However, the results of these studies are very different. We explored the reasons for the contradictory conclusions and provided some suggestions for future research on the gender differences in genetic underpinnings of depression.

Serotonergic influence on depressive symptoms and trait anxiety is mediated by negative life events and frontal activation in children and adolescents

Depression and anxiety are common in childhood and adolescence. Even though cardinal symptoms differ, there is a considerable overlap regarding the pathogenic influence of serotonergic innervation, negative life experience, disturbed emotion perception/affect regulation, and impaired neural functioning in the fronto-limbic circuit. In this study, we examined the effect of the 5-HTTLPR/rs25531 genotype on depressive symptoms and trait anxiety under the consideration of the amount of negative life events in healthy children and adolescents (N = 389). In a subsample of 49 subjects, we performed fMRI to add fronto-limbic brain activation as a second interacting factor. Across all subjects, negative life events moderated the influence of the 5-HTTLPR/rs25531 genotype on both depressive symptoms and trait anxiety. In the fMRI subsample, 5-HTTLPR/rs25531 S + S/L_G + S/L_A + L_GL_A + L_GL_G genotype-associated left middle frontal gyrus (MFG) activation mediated the influence of 5-HTTLPR/rs25531 genotype on depressive symptoms, however, only in combination with negative life events. Genetic influence on trait anxiety was predominantly mediated by negative life events; only L_AL_A genotype-specific activation in the right MFG worked as a mediator in combination with negative life events. The present findings hint towards distinct mechanisms mediating the influence of 5-HTTLPR/rs25531 genotype on depressive symptoms and anxiety, with negative life events playing a crucial role in both phenotypes. With regard to depressive symptoms, however, this influence was only visible in combination with MFG activation, whereas, in anxiety, it was independent of brain activation.

Asenapine in the Treatment of Bipolar Depression

OBJECTIVES

Asenapine, a potent serotonin 7 (5-HT₇) receptor antagonist, was examined for efficacy as an antidepressant in depressed bipolar subjects. It was predicted that subjects with the genetic variant of the short form of the serotonin transporter (5HTTR) would be more likely to respond.

EXPERIMENTAL DESIGN

A subset of patients participating in a randomized, placebo-controlled study of the efficacy of asenapine in bipolar I depression also underwent genetic testing for the 5HTTR. Montgomery Åsberg Depression Rating Scale (MADRS) score was ≥ 26 prior to randomization to asenapine or placebo for 8 weeks. Gene testing was performed before breaking the blind.

PRINCIPAL OBSERVATIONS

Nine patients completing the study also underwent gene testing. At study end, the average MADRS improvement was -19.80 ± SD 8.59 for the 4 people randomized to asenapine and -3.80 ± 9.01 for the 5 people receiving placebo (P = 0.021, t = 2.88). Anxiety, as measured by the Hamilton Anxiety Rating Scale (HAM-A), also improved in asenapine-treated patients (-15.40 ± 6.15 vs. -2.80 ± 7.95, P = 0.023, t = 2.803). Six participants had the short form of the 5HTTR, and it is believed they influenced the significant outcome in this small sample.

CONCLUSIONS

While this is a very small sample, asenapine appears to have a beneficial effect on both depression and anxiety in depressed bipolar I patients compared to treatment with placebo. Due to the large fraction of subjects with the short form, the hypothesis that the SF-5HTTR might increase asenapine response could not be adequately tested.

Childhood factors associated with increased risk for mood episode recurrences in bipolar disorder-A systematic review

BACKGROUND

Bipolar Disorder (BD) is a recurrent illness associated with high morbidity and mortality. The frequency of mood episode recurrence in BD is highly heterogeneous and significantly impacts the person's psychosocial functioning and well-being. Understanding the factors associated with mood recurrences could inform the prognosis and treatment. The objective of this review is to summarize the literature on factors, present during childhood, that influence recurrence.

METHODOLOGY

A systematic review of PubMed (1946-2017) and PsycINFO (1884-2017) databases was conducted to identify candidate studies. Search terms included bipolar disorder, episodes, predictors, recurrences, and course. Study characteristics, risk for bias, and factors associated with recurrence were coded by two raters according to predetermined criteria.

RESULTS

Twenty child studies and 28 adult studies that retrospectively evaluated childhood variables associated with mood recurrences were included. Early age of onset, low socioeconomic status, comorbid disorders, inter-episode subsyndromal mood symptoms, BD-I/II subtypes, presence of stressors, and family history of BD were associated with higher number of recurrences.

LIMITATIONS

Risk factors and mood recurrences were assessed and defined in different ways, limiting generalizability.

CONCLUSION

Multiple factors are associated with increased risk of mood episode recurrence in BD. Interventions targeting modifiable factors could reduce the impact of BD. For example, treatment of comorbid disorders and subsyndromal mood symptoms, coupled with appropriate cognitive behavioral and family-focused therapies could ameliorate risk related to many clinical factors. When coupled with social services to address environmental factors, the number of episodes could be reduced and the course of BD significantly improved.

The influence of genetic factors on personality and coping with stress among healthy late reproductive age women

Background

Psychological stress is a factor which predisposes people to many somatic and mental disorders. Women are at a significantly higher risk of stress than men, and their reactions to stress are stronger. Personality traits are thought to play a special role in the psychology of stress and may be crucial for the choice of a stress-coping strategy. Considering that stress is so common in everyday life, an attempt to understand how stress-coping styles are related to personality and genetic factors acquires special significance.

Purpose

The aim of this study was to analyze stress-coping styles and personality traits in healthy late reproductive age women with regard to genetic factors.

Patients and methods

The study involved 345 healthy late reproductive age women from northwest Poland, whose mean age was 42.3±4.5 years. The study was conducted using The Coping Inventory for Stressful Situations, The Neuroticism-Extraversion-Openness Five--Factor Inventory, and genetic testing.

Results

There were neither statistically significant relationships between personality traits and the genotype distribution of the 30-bp VNTR polymorphism in the MAO-A promoter region, nor between stress-coping styles and the genotype distribution of the 30-bp VNTR polymorphism in the MAO-A promoter region.

Conclusion

Based on the results, all personality traits statistically significantly correlated with the choice of task-oriented coping and emotion-oriented coping. Some of personality traits are genetically determined. The choice of a stress-coping style was significantly related to personality traits. A direct influence of genetic factors on the choice of a stress-coping style was not confirmed in our study.

Neural Response to Pleasant Pictures Moderates Prospective Relationship Between Stress and Depressive Symptoms in Adolescent Girls

Adolescent girls are at increased risk for depression, which is thought to result from the interaction of biological vulnerabilities and life stressors common to adolescent girls. A blunted late positive potential (LPP) to emotional stimuli (i.e., pleasant and unpleasant) has been associated with depressive symptoms and risk. The current study of adolescent girls examines the moderating effects of the LPP, a candidate biomarker of depression, of the link between life stress and increases in depressive symptoms over 1 year. We measured LPP to pleasant and unpleasant pictures from the International Affective Picture Set among 143 predominantly Caucasian adolescent girls ages 8 to 14, who also reported on the frequency of common life stressors. Self-reported depressive symptoms were assessed both at baseline and 1 year after the initial lab visit. The LPP to pleasant pictures moderated the relationship between baseline life stressors and the change in depressive symptoms. Specifically, life stress was associated with increases in depressive symptoms when the LPP to pleasant pictures was blunted, whereas life stress was associated with decreases in depressive symptoms when the LPP to pleasant pictures was potentiated. These effects showed some specificity to family and school-related stressors and to anhedonic and efficacy-related depressive symptoms. A similar pattern, though not statistically significant, was found for the LPP to unpleasant pictures. Together, these findings suggest that the LPP to pleasant pictures may represent a useful biomarker in identifying individuals at greatest risk of experiencing depressive symptoms following stress.

Interactive effects of genetic polymorphisms and childhood adversity on brain morphologic changes in depression

The etiology of depression is characterized by the interplay of genetic and environmental factors and brain structural alteration. Childhood adversity is a major contributing factor in the development of depression. Interactions between childhood adversity and candidate genes for depression could affect brain morphology via the modulation of neurotrophic factors, serotonergic neurotransmission, or the hypothalamus-pituitary-adrenal (HPA) axis, and this pathway may explain the subsequent onset of depression. Childhood adversity is associated with structural changes in the hippocampus, amygdala, anterior cingulate cortex (ACC), and prefrontal cortex (PFC), as well as white matter tracts such as the corpus callosum, cingulum, and uncinate fasciculus. Childhood adversity showed an interaction with the brain-derived neurotrophic factor (BDNF) gene Val66Met polymorphism, serotonin transporter-linked promoter region (5-HTTLPR), and FK506 binding protein 51 (FKBP5) gene rs1360780 in brain morphologic changes in patients with depression and in a non-clinical population. Individuals with the Met allele of BDNF Val66Met and a history of childhood adversity had reduced volume in the hippocampus and its subfields, amygdala, and PFC and thinner rostral ACC in a study of depressed patients and healthy controls. The S allele of 5-HTTLPR combined with exposure to childhood adversity or a poorer parenting environment was associated with a smaller hippocampal volume and subsequent onset of depression. The FKBP5 gene rs160780 had a significant interaction with childhood adversity in the white matter integrity of brain regions involved in emotion processing. This review identified that imaging genetic studies on childhood adversity may deepen our understanding on the neurobiological background of depression by scrutinizing complicated pathways of genetic factors, early psychosocial environments, and the accompanying morphologic changes in emotion-processing neural circuitry.

The Impact of Religion on Family Functioning in Low-Income African American Families With Adolescents

The current study explores the association between religion and family functioning. Specifically, this study examined whether two aspects of religion, social religious support (from clergy and members of the congregation) and support from God (or spirituality), were related to frequency of household routines and parenting strategies as reported by both parents and adolescents, as well as adolescent problem behaviors. The sample consisted of 115 low-income African American mother-adolescent (age 14-18 years) dyads. Families were recruited as part of a larger study on the lives of low-income African American families with adolescents. Results indicated that higher levels of social religious support and spirituality were associated with increased levels of family routine as reported by caregivers. These results highlight the important roles relationships with God and other church members may play in supporting the lives of low-income African American parents and their children.

Sex differences modulating serotonergic polymorphisms implicated in the mechanistic pathways of risk for depression and related disorders

Despite consistent observations of sex differences in depression and related emotional disorders, we do not yet know how these sex differences modulate the effects of genetic polymorphisms implicated in risk for these disorders. This Mini-Review focuses on genetic polymorphisms of the serotonergic system to illustrate how sex differences might modulate the neurobiological pathways involved in the development of depression. We consider the interacting role of environmental factors such as early-life stress. Given limited current knowledge about this topic, we highlight methodological considerations, challenges, and guidelines for future research. © 2016 Wiley Periodicals, Inc.

Depression as a risk factor for Alzheimer's disease: Genes, steroids, cytokines and neurogenesis - What do we need to know?

Depression (MDD) is prodromal to, and a component of, Alzheimer's disease (AD): it may also be a trigger for incipient AD. MDD is not a unitary disorder, so there may be particular subtypes of early life MDD that pose independent high risks for later AD, though the identification of these subtypes is problematical. There may either be a common pathological event underlying both MDD and AD, or MDD may sensitize the brain to a second event ('hit') that precipitates AD. MDD may also accelerate brain ageing, including altered DNA methylation, increased cortisol but decreasing DHEA and thus the risk for AD. So far, genes predicting AD (e.g. APOEε4) are not risk factors for MDD, and those implicated in MDD (e.g. SLC6A4) are not risks for AD, so a common genetic predisposition looks unlikely. There is as yet no strong indication that an epigenetic event occurs during some forms of MDD that predisposes to later AD, though the evidence is limited. Glucocorticoids (GCs) are disturbed in some cases of MDD and in AD. GCs have marked degenerative actions on the hippocampus, a site of early β-amyloid deposition, and rare genetic variants of GC-regulating enzymes (e.g. 11β-HSD) predispose to AD. GCs also inhibit hippocampal neurogenesis and plasticity, and thus episodic memory, a core symptom of AD. Disordered GCs in MDD may inhibit neurogenesis, but the contribution of diminished neurogenesis to the onset or progression of AD is still debated. GCs and cytokines also reduce BDNF, implicated in both MDD and AD and hippocampal neurogenesis, reinforcing the notion that those cases of MDD with disordered GCs may be a risk for AD. Cytokines, including IL1β, IL6 and TNFα, are increased in the blood in some cases of MDD. They also reduce hippocampal neurogenesis, and increased cytokines are a known risk for later AD. Inflammatory changes occur in both MDD and AD (e.g. raised CRP, TNFα). Both cytokines and GCs can have pro-inflammatory actions in the brain. Inflammation (e.g. microglial activation) may be a common link, but this has not been systematically investigated. We lack substantial, rigorous and comprehensive follow-up studies to better identify possible subtypes of MDD that may represent a major predictor for later AD. This would enable specific interventions during critical episodes of these subtypes of MDD that should reduce this substantial risk.

5-HTTLPR and gender differences in affective disorders: A systematic review

BACKGROUND

Serotonin transporter-linked polymorphic region (5-HTTLPR) variants have been extensively studied in psychiatric disorders. Although gender effects have been reported, they have not been comprehensively reviewed. The aim of our study was to summarize literature findings on 5-HTTLPR and gender differences in affective disorders.

METHODS

A systematic search of PubMed, ISI Web of Knowledge, and PsycINFO databases was performed for dates until January 2015. The included articles (n=78) analyzed the association between 5-HTTLPR and affective spectrum disorders, taking into account gender. The quality of each study was assessed through STROBE and CONSORT.

RESULTS

5-HTTLPR modulation of affective disorders varied by gender. The S allele (or SS genotype) seemed to be differently associated with an increased risk of depression, depressive symptoms, anxiety traits and symptoms, and symptoms of internalizing behavior among women and an increased risk of aggressiveness, conduct disorder and symptom counts of externalizing behavior among men. Moreover, the presence of stressful life events reinforced the association. Interestingly, these differences seemed to begin with adolescence and were not consistent among the elderly, suggesting a plausible role of hormonal fluctuations.

LIMITATIONS

The review is limited by the small number of included papers, due to the paucity of information in the literature regarding 5-HTTLPR and gender.

CONCLUSIONS

5-HTTLPR variants may exert a differential modulation on a number of features depending on gender. Further studies are needed to more deeply investigate the effect of 5-HTTLPR×gender on the modulation of affective disorders.

Tryptophan Biochemistry: Structural, Nutritional, Metabolic, and Medical Aspects in Humans

L-Tryptophan is the unique protein amino acid (AA) bearing an indole ring: its biotransformation in living organisms contributes either to keeping this chemical group in cells and tissues or to breaking it, by generating in both cases a variety of bioactive molecules. Investigations on the biology of Trp highlight the pleiotropic effects of its small derivatives on homeostasis processes. In addition to protein turn-over, in humans the pathways of Trp indole derivatives cover the synthesis of the neurotransmitter/hormone serotonin (5-HT), the pineal gland melatonin (MLT), and the trace amine tryptamine. The breakdown of the Trp indole ring defines instead the "kynurenine shunt" which produces cell-response adapters as L-kynurenine, kynurenic and quinolinic acids, or the coenzyme nicotinamide adenine dinucleotide (NAD(+)). This review aims therefore at tracing a "map" of the main molecular effectors in human tryptophan (Trp) research, starting from the chemistry of this AA, dealing then with its biosphere distribution and nutritional value for humans, also focusing on some proteins responsible for its tissue-dependent uptake and biotransformation. We will thus underscore the role of Trp biochemistry in the pathogenesis of human complex diseases/syndromes primarily involving the gut, neuroimmunoendocrine/stress responses, and the CNS, supporting the use of -Omics approaches in this field.

Genetic Susceptibility and Sleep Disturbance in Black Mothers of Preterm Infants: An Exploratory Study

Serotonin (5HT) is involved in emotion and sleep regulation and the 5HT transporter (5HTT) regulates 5HT function. A common 44-base pair deletion (short allele) or insertion (long allele) polymorphism in the promoter region of 5HTT (5-HTTLPR) is differentially associated with 5HTT transcription efficiency. Under stressful conditions, the short allele of 5-HTTLPR has been associated with depression and sleep disturbance. Black women are at higher risk for preterm labor and depressive symptoms. Thus, this exploratory study aimed to examine whether depressive symptoms and sleep disturbance in Black mothers would vary as a function of the 5-HTTLPR genotype when they faced the stress of infant hospitalization after preterm birth at early postpartum. A total of 30 Black mothers filled out a battery of questionnaires, including the Perceived Stress Scale, Edinburgh Postnatal Depression Scale, and General Sleep Disturbance Scale. A wrist actigraph was used to assess total sleep time and circadian activity rhythms. Buccal cells from saliva were collected to test the 5-HTTLPR genotype. Results showed that about 38% of the mothers were heterozygous for the short (S/L) allele, and 62% were homozygous for the long (L/L) allele. Mothers’ perceived global stress, depressive symptoms, and circadian activity rhythms did not vary with their 5-HTTLPR genotypes. Unexpectedly, mothers with the L/L allele reported greater sleep disturbances than those with the S/L allele. Ethnic specificity in genetic susceptibility to stress was discussed.

The Involvement of Genes in Adolescent Depression: A Systematic Review

Numerous studies have reported on the roles of genetic factors in the development of depression in adolescents and young adults. However, there are few systematic reviews that update our understanding of adolescent depression with the biological findings identifying the roles of gene expression and/or polymorphism(s). This review systematically summarized the findings that clearly identified the contribution of a gene to the risk of depression in adolescents between the ages of 10 and 19 years old and young adults between the ages of 20 and 25 years old. Data were obtained through searching PubMed, Embase, and Web of Science. A total of 47 studies on early adolescence and three studies on young adults were included in the current review. Most articles studied genes in the serotonergic system (n = 26), dopaminergic system (n = 3), and the Brain-derived neurotropic factor (BDNF) gene (n = 12). 92.3% of studies (24/26) identified positive associations of 5-HTTLPR polymorphism with depressive illness or depressive symptoms. 83.3% of studies (10/12) found positive association between BDNF Val66Met genotype and adolescent depressive symptoms. More studies should be conducted on the 18 genes reported in a few studies to clarify their roles in the risk for adolescent depression.

Depression from childhood into late adolescence: Influence of gender, development, genetic susceptibility, and peer stress

Depression is a debilitating mental illness with clear developmental patterns from childhood through late adolescence. Here, we present data from the Gene Environment Mood (GEM) study, which used an accelerated longitudinal cohort design with youth (N = 665) starting in 3rd, 6th, and 9th grades, and a caretaker, who were recruited from the general community, and were then assessed repeatedly through semistructured diagnostic interviews every 6 months over 3 years (7 waves of data) to establish and then predict trajectories of depression from age 8 to 18. First, we demonstrated that overall prevalence rates of depression over time, by age, gender, and pubertal status, in the GEM study closely match those trajectories previously obtained in past developmental epidemiological research. Second, we tested whether a genetic vulnerability-stress model involving 5-HTTLPR and chronic peer stress was moderated by developmental factors. Results showed that older aged adolescents with SS/SL genotype, who experienced higher peer chronic stress over 3 years, were the most likely to be diagnosed with a depressive episode over time. Girls experiencing greater peer chronic stress were the most likely to develop depression. This study used repeated assessments of diagnostic interviewing in a moderately large sample of youth over 3 years to show that depression rates increase in middle to late adolescence, or postpubertally, and that the gender difference in depression emerges earlier in adolescence (age 12.5), or postpubertally. Additionally, genetically susceptible older adolescents who experience chronic peer stress were the most likely to become depressed over time.

Sensitizing effect of early adversity on depressive reactions to later proximal stress: Moderation by polymorphisms in serotonin transporter and corticotropin releasing hormone receptor genes in a 20-year longitudinal study

Previous research supports gene-environment interactions for polymorphisms in the corticotropin hormone receptor 1 gene (CRHR1) and the serotonin transporter gene linked polymorphic region (5-HTTLPR) in predicting depression, but it has rarely considered genetic influences on stress sensitization processes, whereby early adversities (EA) increase depressive reactivity to proximal stressors later in life. The current study tested a gene-environment-environment interaction (G × E × E; specifically, gene-EA-proximal stress interaction) model of depression in a 20-year longitudinal study. Participants were assessed prospectively for EA up to age 5 and recent chronic stress and depressive symptoms at age 20 and genotyped for CRHR1 single nucleotide polymorphism rs110402 and 5-HTTLPR. EA predicted stronger associations between recent chronic stress and depression, and the effect was moderated by genes. CRHR1 A alleles and 5-HTTLPR short alleles were associated with greater stress sensitization (i.e., greater depressive reactivity to chronic stress for those also exposed to high levels of EA). The results are consistent with the notion that EA exposure results in neurobiological and cognitive-emotional consequences (e.g., altered hypothalamic-pituitary-adrenal axis functioning), leading to emotional distress in the face of recent stressors among those with certain genetic characteristics, although further research is needed to explore explanatory mechanisms.

Individual, school-related and family characteristics distinguish co-occurrence of drinking and depressive symptoms in very young adolescents

INTRODUCTION AND AIMS

Alcohol misuse and depressed mood are common during early adolescence, and comorbidity of these conditions in adulthood is associated with poorer health and social outcomes, yet little research has examined the co-occurrence of these problems at early adolescence. This study assessed risky and protective characteristics of pre-teens with concurrent depressed mood/early alcohol use in a large school-based sample.

DESIGN AND METHODS

School children aged 10-14 years (n = 7289) from late primary and early secondary school classes in government, Catholic and independent sectors participated with parental consent in the cross-sectional Healthy Neighbourhoods Study. Key measures included depressed mood, recent alcohol use, school mobility, family relationship quality, school engagement and coping style. Multinomial logistic regression analyses were used to identify school and family-related factors that distinguished those with co-occurring drinking and depressive symptoms from those with either single condition. Gender and school-level interactions for each factor were evaluated.

RESULTS

Co-occurring conditions were reported by 5.7% of students [confidence interval (CI)95 5.19, 6.19]. Recent drinkers were more likely than non-drinkers to have symptoms consistent with depression (odds ratio 1.80; CI95 1.58, 2.03). Low school commitment was associated with co-occurring drinking/depressive symptoms (odds ratio 2.86; CI95 2.25, 3.65 compared with null condition). This association appeared to be weaker in the presence of adaptive stress-coping skills (odds ratio 0.18; CI95 0.14, 0.23).

CONCLUSIONS

We have identified factors that distinguish pre-teens with very early co-occurrence of drinking and depressed mood, and protective factors with potential utility for school-based prevention programmes targeting these conditions. [Salom CL, Kelly AB, Alati R, Williams GM, Patton GC, Williams JW. Individual, school-related and family characteristics distinguish co-occurrence of drinking and depressive symptoms in very young adolescents. Drug Alcohol Rev 2016;35:387-396].

Genetic moderation of the association between adolescent romantic involvement and depression: Contributions of serotonin transporter gene polymorphism, chronic stress, and family discord

Studies support a link between adolescent romantic involvement and depression. Adolescent romantic relationships may increase depression risk by introducing chronic stress, and genetic vulnerability to stress reactivity/emotion dysregulation may moderate these associations. We tested genetic moderation of longitudinal associations between adolescent romantic involvement and later depressive symptoms by a polymorphism in the serotonin transporter linked polymorphic region gene (5-HTTLPR) and examined contributory roles of chronic stress and family discord. Three hundred eighty-one youth participated at ages 15 and 20. The results indicated that 5-HTTLPR moderated the association between age 15 romantic involvement and age 20 depressive symptoms, with strongest effects for short homozygotes. Conditional process analysis revealed that chronic stress functioned as a moderated mediator of this association, fully accounting for the romantic involvement-depression link among short/short genotypes. Also, romantic involvement predicted later depressive symptoms most strongly among short-allele carriers with high family discord. The results have important implications for understanding the romantic involvement-depression link and the behavioral and emotional correlates of the 5-HTTLPR genotype.

Mice lacking integrin β3 expression exhibit altered response to chronic stress

Recent studies indicate multiple roles for integrin αvβ3 in adult neurons, including response to pharmacological agents such as cocaine and selective serotonin reuptake inhibitors. In this study, we examined the role of the integrin β3 gene (Itgb3) in the response to environmental stimuli by subjecting Itgb3^+/+ and Itgb3^-/- mice to unpredictable chronic mild stressors. We found that genetic abrogation of integrin β3 expression elicits an exaggerated vulnerability to chronic unpredictable stress in the open field test. In this test, chronic stress elicited significant decreases in stereotypic behavior and horizontal locomotor activity, including increases in anxiety behaviors. Mild chronic stress led to reductions in dopamine turnover in midbrains of Itgb3^+/+, but not Itgb3^-/- mice, suggesting a disruption of stress-dependent regulation of DA homeostasis. Chronic stress elicited altered synaptic expression of syntaxin and synaptophysin in midbrains of Itgb3^-/- mice, when compared to Itgb3^+/+. Semi-quantitative Western blot studies revealed that the synaptic expression, but not total tissue expression, of multiple signaling proteins is correlated with integrin αv levels in the midbrain. Moreover, loss of integrin β3 expression modifies this correlation network. Together, these findings demonstrate that Itgb3^-/- mice display a pattern of changes indicating disrupted regulation of midbrain synaptic systems involved in conferring resilience to mild stressors.

Role of hippocampus mitogen-activated protein kinase phosphatase-1 mRNA expression and DNA methylation in the depression of the rats with chronic unpredicted stress

Stressful life events especially the chronic unpredictable stress are the obvious precipitating factors of depression. The biological information transduction in cells plays an important role in the molecular biology mechanism of depression. Mitogen-activated protein kinase phosphatase-1 (MKP-1) regulates the cell physiological activity and involves in the adjustment of neural plasticity, function, and survival. This experiment tried to explore the possible effects of MKP-1 in hippocampus on depression of rats by determining the expression of MKP-1 mRNA and DNA methylation in MKP-1 gene promoter. The animal model was established by chronic unpredictable stress, and evaluated by open-field test and weight changes. All the rats were divided into the sham stimulation, the physiological saline, and the fluoxetine (1.25, 2.50, and 5.00 mg/kg) groups randomly. The expression of MKP-1 mRNA in the hippocampus was measured by RT-PCR and the methylation of MKP-1 promoter DNA was detected by COBRA. The chronic unpredicted stress (1) increased the animal movement scores in open-field test, and fluoxetine could prevent this increasement; (2) increased the body weight, and fluoxetine could not prevent this increasement; and (3) increased MKP-1 mRNA expression in the hippocampus, and fluoxetine could prevent it. However, fluoxetine did not influence the DNA methylation of MKP-1 gene promoter in the hippocampus during the chronic unpredicted stress. MKP-1 in the hippocampus might be involved in the etiology of depression, and DNA methylation of MKP-1 gene promoter in the hippocampus did not related with the depression.

Biomarkers of intergenerational risk for depression: a review of mechanisms in longitudinal high-risk (LHR) studies

BACKGROUND

Longitudinal research is critical for understanding the biological mechanisms underlying the development of depression. Researchers recruit high-risk cohorts to understand how risk is transmitted from one generation to the next. Biological measurements have been incorporated into these longitudinal high-risk (LHR) studies in order to illuminate mechanistic pathways.

METHODS

To frame our review, we first present heritability estimates along the gene-by-environment continuum as a foundation. We then offer a Biomarkers of Intergenerational Risk for Depression (BIRD) model to describe the multiple hits individuals at risk receive and to allow for greater focus on the interactive effects of markers. BIRD allows for the known multifinality of pathways towards depression and considers the context (i.e., environment) in which these mechanisms emerge. Next, we review the extant LHR cohort studies that have assessed central nervous system (electroencephalography (EEG), neuroimaging), endocrine (hypothalamic-pituitary-adrenal axis (HPA)/cortisol), autonomic (startle, heart rate), genetic, sleep, and birth characteristics.

RESULTS

Results to date, in conjunction with the proposed model, point towards several pathways of discovery in understanding mechanisms, providing clear direction for future research examining potential endophenotypes.

LIMITATIONS

Our review is based on relatively narrow inclusion and exclusion criteria. As such, many interesting studies were excluded, but this weakness is offset by strengths such as the increased reliability of findings.

CONCLUSIONS

Blanket prevention programs are inefficient and plagued by low effect sizes due to low rates of actual conversion to disorder. The inclusion of biomarkers of risk may lead to enhanced program efficiency by targeting those at greatest risk.

Burnout-depression overlap: a review

Whether burnout is a form of depression or a distinct phenomenon is an object of controversy. The aim of the present article was to provide an up-to-date review of the literature dedicated to the question of burnout-depression overlap. A systematic literature search was carried out in PubMed, PsycINFO, and IngentaConnect. A total of 92 studies were identified as informing the issue of burnout-depression overlap. The current state of the art suggests that the distinction between burnout and depression is conceptually fragile. It is notably unclear how the state of burnout (i.e., the end stage of the burnout process) is conceived to differ from clinical depression. Empirically, evidence for the distinctiveness of the burnout phenomenon has been inconsistent, with the most recent studies casting doubt on that distinctiveness. The absence of consensual diagnostic criteria for burnout and burnout research's insufficient consideration of the heterogeneity of depressive disorders constitute major obstacles to the resolution of the raised issue. In conclusion, the epistemic status of the seminal, field-dominating definition of burnout is questioned. It is suggested that systematic clinical observation should be given a central place in future research on burnout-depression overlap.

Genetic susceptibility to family environment: BDNF Val66met and 5-HTTLPR influence depressive symptoms

Functional genetic polymorphisms associated with Brain-Derived Neurotrophic Factor (BDNF) and serotonin (5-HTTLPR) have demonstrated associations with depression in interaction with environmental stressors. In light of evidence for biological connections between BDNF and serotonin, it is prudent to consider genetic epistasis between variants in these genes in the development of depressive symptoms. The current study examined the effects of val66met, 5-HTTLPR, and family environment quality on youth depressive symptoms in adolescence and young adulthood in a longitudinal sample oversampled for maternal depression history. A differential susceptibility model was tested, comparing the effects of family environment on depression scores across different levels of a cumulative plasticity genotype, defined as presence of both, either, or neither plasticity alleles (defined here as val66met Met and 5-HTTLPR 'S'). Cumulative plasticity genotype interacted with family environment quality to predict depression among males and females at age 15. After age 15, however, the interaction of cumulative plasticity genotype and early family environment quality was only predictive of depression among females. Results supported a differential susceptibility model at age 15, such that plasticity allele presence was associated with more or less depressive symptoms depending on valence of the family environment, and a diathesis-stress model of gene-environment interaction after age 15. These findings, although preliminary because of the small sample size, support prior results indicating interactive effects of 5-HTTLPR, val66met, and environmental stress, and suggest that family environment may have a stronger influence on genetically susceptible women than men.

Comparing chronic interpersonal and noninterpersonal stress domains as predictors of depression recurrence in emerging adults

Understanding how persistent interpersonal difficulties distinctly affect the course of major depressive disorder (MDD) during emerging adulthood is critical, given that early experiences impact future coping resources and functioning. Research on stress and MDD has mostly concentrated on stressful life events, while chronic stress largely has not been explored. The present study examined interpersonal (intimate relationship, close friendships, social life, family relationships) and noninterpersonal (academic, work, financial, personal health, and family members' health) domains of chronic stress as time-varying predictors of depressive recurrence in emerging adults. Baseline assessments identified previously depressed emerging adults (N = 119), who subsequently completed 6-month, 12-month and 18-month follow-up interviews to determine chronic stress experiences and onset of new major depressive episodes. Survival analyses indicated that time-varying total chronic stress and chronic interpersonal stress predicted higher risk for depression recurrence; however, chronic noninterpersonal stress was not associated with recurrence. Intimate relationship stress, close friendship stress, family relationship stress, personal health, and family members' health independently predicted MDD recurrence, over and above well-established depression risk factors of dysfunctional cognitions and personality disorder symptoms. Evidence that interpersonal stress could have substantial impact on course of depression is consistent with theories of emerging adulthood, a time when young people are individuating from the family and experiencing significant social transition.

An update on the interaction between the serotonin transporter promoter variant (5-HTTLPR), stress and depression, plus an exploration of non-confirming findings

In the three years since the most recent meta-analysis of the association between the serotonin transported promoter polymorphism (5-HTTLPR), stress and the development of depression, another 27 studies have been published on this issue, which is an increase of 50% more studies than were previously reviewed. In addition, previous findings of inconsistency of results across studies argued for further exploration of this relationship. From the 81 studies identified to June 2013, the significant relationship between the short form of the 5-HTTLPR was confirmed (p=.0000009), which is stronger than the relationship reported in the most recent meta-analysis in 2011. However, nearly 26% of the 81 studies reviewed failed to show any significant association between the 5-HTTLPR, stress and depression, and four studies found opposite results to those expected. Examination of the methodologies of all studies failed to indicate any flaws in the opposite or unequivocal studies, and the latter had larger sample sizes than those studies which supported the expected association, arguing that the null results were not an outcome of insufficient statistical power. The need to consider aspects of samples and measures of depression, particularly the presence of subtypes of depression in future research is discussed.

Differential susceptibility in longitudinal models of gene-environment interaction for adolescent depression

Although family support reliably predicts the development of adolescent depression and suicidal behaviors, relatively little is known about the interplay of family support with potential genetic factors. We tested the association of the 44 base pair polymorphism in the serotonin transporter linked promoter region gene (5-HTTLPR), family support (i.e., cohesion, communication, and warmth), and their interaction with self-reported depression symptoms and risk for suicide in 1,030 Caucasian adolescents and young adults from the National Longitudinal Study of Adolescent Health. High-quality family support predicted fewer symptoms of depression and reduced risk for suicidality. There was also a significant interaction between 5-HTTLPR and family support for boys and a marginally significant interaction for girls. Among boys with poor family support, youth with at least one short allele had more symptoms of depression and a higher risk for suicide attempts relative to boys homozygous for the long allele. However, in the presence of high family support, boys with the short allele had the fewest depression symptoms (but not suicide attempts). Results suggest that the short allele may increase reactivity to both negative and positive family influences in the development of depression. We discuss the potential role of interactive exchanges between family support and offspring genotype in the development of adolescent depression and suicidal behaviors.

Does relational dysfunction mediate the association between anxiety disorders and later depression? Testing an interpersonal model of comorbidity

BACKGROUND

Anxiety disorders tend to precede onset of comorbid depression. Several researchers have suggested a causal role for anxiety in promoting depressive episodes, but few studies have identified specific mechanisms. The current study proposes an interpersonal model of comorbidity, where anxiety disorders disrupt interpersonal functioning, which in turn elevates risk for depression.

METHODS

At age 15 (T1), 815 adolescents oversampled for maternal depression completed diagnostic interviews, social chronic stress interviews, and self-report measures. At age 20 (T2), participants repeated all measures and reported on self-perceived interpersonal problems. At approximately age 23 (T3), a subset of participants (n = 475) completed a self-report depressive symptoms measure.

RESULTS

Consistent with other samples, anxiety disorders largely preceded depressive disorders. Low sociability and interpersonal oversensitivity mediated the association between T1 social anxiety disorder and later depression (including T2 depressive diagnosis and T3 depressive symptoms), controlling for baseline. Interpersonal oversensitivity and social chronic stress similarly mediated the association between generalized anxiety disorder before age 15 and later depression.

CONCLUSIONS

Interpersonal dysfunction may be one mechanism through which anxiety disorders promote later depression, contributing to high comorbidity rates.

A Preliminary Examination of the Relationship Between the 5-HTTLPR and Childhood Emotional Abuse on Depressive Symptoms in 10-12-Year-Old Youth

Childhood emotional abuse (CEA) is a pervasive problem associated with negative sequelae such as elevated depressive symptoms. Key stress-related genes, such as the 5-HTTLPR polymorphism, interact with childhood abuse to produce elevated depressive symptoms in older adolescent girls, but not in older adolescent boys. To date, studies have not examined this relationship as a function of CEA specifically or among younger adolescents. To extend prior work, we examined the effects of the 5-HTTLPR and CEA on depressive symptoms among 10-12-year-old youth. Based on previous findings, we expected a main effect of CEA on depressive symptoms among all youth, but only expected an interactive effect between the 5-HTTLPR and CEA on depressive symptoms in girls. In the current study, 222 youth (mean age 11.02 years, 44.1% girls, 51.6% Caucasian, 33.0% African American, 2.7% Latino, and 12.7% other) and their parent(s)/guardian(s) completed the Revised Child Anxiety and Depression Scale and the Emotional Abuse subscale of the Childhood Trauma Questionnaire and provided saliva samples for genotyping the 5-HTTLPR. Results indicate that CEA, but not the 5-HTTLPR, was related to elevated depressive symptoms among boys. Among girls, each copy of the s allele of the 5-HTTLPR was related to increased depressive symptoms, but only for those who had experienced CEA. Our results extend prior findings by specifically examining CEA and by focusing on 10-12-year-old youth. These results, although preliminary, suggest that focusing on the interplay between putative genetic markers and a broader range of environmental events, such as CEA, might allow researchers to determine factors differentially influencing the later emergence of sex differences in depressive symptoms.

Gene-environment interactions and intermediate phenotypes: early trauma and depression

This review focuses on current research developments in the study of gene by early life stress (ELS) interactions and depression. ELS refers to aversive experiences during childhood and adolescence such as sexual, physical or emotional abuse, emotional or physical neglect as well as parental loss. Previous research has focused on investigating and characterizing the specific role of ELS within the pathogenesis of depression and linking these findings to neurobiological changes of the brain, especially the stress response system. The latest findings highlight the role of genetic factors that increase vulnerability or, likewise, promote resilience to depression after childhood trauma. Considering intermediate phenotypes has further increased our understanding of the complex relationship between early trauma and depression. Recent findings with regard to epigenetic changes resulting from adverse environmental events during childhood promote current endeavors to identify specific target areas for prevention and treatment schemes regarding the long-term impact of ELS. Taken together, the latest research findings have underscored the essential role of genotypes and epigenetic processes within the development of depression after childhood trauma, thereby building the basis for future research and clinical interventions.

Differential impact of cumulative SES risk on methylation of protein-protein interaction pathways as a function of SLC6A4 genetic variation in African American young adults

Exposure to cumulative SES risk in childhood may interact with variability at the serotonin transporter linked polymorphic region (5HTTLPR) to alter DNA methylation across interacting sets of proteins. DNA was obtained from 388 African Americans at age 19. Genotype at the 5HTTLPR was determined, and methylation ratios for C-phosphate-G (CpG) residues were assessed. Exposure to cumulative SES risk was determined using repeated parental reports at ages 11-13. At high SES risk, CpG methylation patterns indicated altered cellular stress response in women, but not men, who carried a short allele at the 5HTTLPR. These changes in methylation patterns may lead to increases in mental and physical health risks. No genotype effect emerged for either women or men at low SES risk. Methylation patterns provide guidance in identifying pathways by which genetic susceptibility is transformed into adverse outcomes years later.

Refining the Candidate Environment: Interpersonal Stress, the Serotonin Transporter Polymorphism, and Gene-Environment Interactions in Major Depression

Meta-analytic evidence supports a gene-environment (G×E) interaction between life stress and the serotonin transporter polymorphism (5-HTTLPR) on depression, but few studies have examined factors that influence detection of this effect, despite years of inconsistent results. We propose that the "candidate environment" (akin to a candidate gene) is key. Theory and evidence implicate major stressful life events (SLEs)-particularly major interpersonal SLEs-as well as chronic family stress. Participants (N = 400) from the Youth Emotion Project (which began with 627 high school juniors oversampled for high neuroticism) completed up to five annual diagnostic and life stress interviews and provided DNA samples. A significant G×E effect for major SLEs and S-carrier genotype was accounted for significantly by major interpersonal SLEs but not significantly by major non-interpersonal SLEs. S-carrier genotype and chronic family stress also significantly interacted. Identifying such candidate environments may facilitate future G×E research in depression and psychopathology more broadly.

Involvement of pGluR1, EAAT2 and EAAT3 in offspring depression induced by prenatal stress

It is widely known that prenatal stress (PS) exposure causes depression-like behaviour to offspring, as well as maladaptive responses including neurobiological and physiological changes. However, the underlying mechanism of PS induced juvenile-onset depression remains largely unravelled. The inadequacies of monoamine deficiency hypothesis, the emerging evidence of altered glutamate neurotransmission in mood disorders, as well as our previous studies inspired us to assess the potential role of glutamatergic system in the pathogenesis of juvenile depression. In this research, we examined the expression of phosphorylated GluR1 subunit of ionotropic receptor alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR), the Na+-dependent glutamate transporters excitatory amino acid transporter 2 (EAAT2) and EAAT3 in the hippocampus, striatum and frontal cortex of 1-month-old rat offspring after mid and late PS exposure. Prenatally stressed offspring rats showed significantly prolonged duration of immobility and shortened immobility latency in tail suspension test. We also detected that PS significantly altered the expression of glutamate receptor and glutamate transporters of these depressed rats. In brief, the changes of phosphorylated GluR1 subunit of AMPAR protein level in the hippocampus and frontal cortex, as well as markedly decreased EAAT2 mRNA expression in the hippocampus, striatum and frontal cortex and EAAT3 mRNA expression in the hippocampus of stressed rats were both observed. These results underpinned that glutamate receptors and glutamate transporters might be involved in the progress of depression-like behaviour in juvenile rat offspring induced by PS.

Interaction between a serotonin transporter gene promoter region polymorphism and stress predicts depressive symptoms in Chinese adolescents: a multi-wave longitudinal study

BACKGROUND

The serotonin transporter (5-HTT) gene may play an important role in the onset and development of mental disorders. Past studies have tested whether a functional polymorphism in the 5-HTT gene linked promoter region (5-HTTLPR) moderated the association between stress and depressive symptoms, but the results of these studies were inconsistent. Thus, the aim of the current study was to examine the interaction between 5-HTTLPR and stress that predict depressive symptoms in Chinese adolescents.

METHODS

A total of 252 healthy adolescents (131 females and 121 males, aged from 14 to 18, mean = 16.00, standard deviation = 0.60) participated in this study. During the initial assessment, all participants completed the Center for Epidemiological Studies Depression Scale (CES-D) and Adolescent Life Events Questionnaire (ALEQ) and were genotyped for the 5-HTTLPR polymorphism. Participants subsequently completed CES-D and ALEQ once every three months during the subsequent 24 months. A multilevel model was used to investigate the 5-HTTLPR × stress interaction in predicting depressive symptoms.

RESULTS

The results indicated no main effect of 5-HTTLPR and a significant 5-HTTLPR × stress interaction in females only. Females with at least one 5-HTTLPR S allele exhibited more depressive symptoms under stressful situations. No significant 5-HTTLPR × stress interaction was found in males.

CONCLUSIONS

In Chinese adolescents, there are gender differences on the interaction between 5-HTTLPR and stress that predict depressive symptoms. The association between stress and depressive symptoms is moderated by 5-HTTLPR in Chinese female adolescents.

Depression persistence and serotonin transporter genotype in adolescents under usual care conditions

OBJECTIVES

Polymorphisms of the serotonin transporter (SERT) gene have been shown to influence the risk for depression. The goal of this study was to investigate a possible effect of SERT polymorphisms on severity and course of depression symptoms in a community sample of adolescents.

METHODS

Community-dwelling adolescents (n=192) ages 13-17 years, who were at risk for depression, were followed for a period of 6 months. Subjects donated a saliva sample for genotyping of the 5-HTTLPR and STin2 VNTR polymorphisms of SERT.

RESULTS

We found no associations between SERT genotype and severity of depressive symptoms at baseline. Depression symptom severity markedly decreased over time. For 5-HTTLPR, we observed a significant interaction between time and genotype, indicating the possibility that heterozygote genotype carriers (s/l) might experience a greater reduction in depression symptoms over time compared with adolescents with the 5-HTTLPR l/l genotype.

CONCLUSIONS

Our study shows that for most community-dwelling adolescents, depressive symptoms decrease over time. A possible interaction effect of time and SERT genotype will require confirmation in larger studies.

Relational security moderates the effect of serotonin transporter gene polymorphism (5-HTTLPR) on stress generation and depression among adolescents

Previous research demonstrates that carriers of the short allele of the serotonin transporter gene (5-HTTLPR) show both greater susceptibility to depression in response to stressful life events and higher rates of generation of stressful events in response to depression. The current study examines relational security (i.e., self-reported beliefs about attachment security) as a moderator of these effects, building on emerging research suggesting that the short allele acts as a marker of sensitivity to the social environment. Participants were 354 Caucasian adolescents oversampled for maternal depression (137 male, 217 female), assessed at ages 15 and 20. Results indicated that the short allele predicted increased stress generation at age 20 among those with low age 15 security but decreased stress generation among those with high security, and revealed a three-way interaction between age 15 depression, age 15 security, and genotype, where depression predicted stress generation only among short allele carriers with low security. Further, among boys only, security interacted with genotype to predict longitudinal changes in depression diagnosis, with the s-allele predicting relative increases in probability of depression among boys with low security but decreases among boys with high security. Results support the notion of the short allele as a marker of social reactivity, and suggest that attachment security may buffer against the genetic vulnerability introduced by the short allele, in line with predictions of the differential susceptibility theory.

G × E interaction and neurodevelopment II. Focus on adversities in paediatric depression: the moderating role of serotonin transporter

In a short series of articles, we will review the evidence for genotype by environment interaction (G × E) in developmental psychopathology. We will focus specifically on the characteristics of types of exposure assessed with respect to both their methods and findings. This article aims to review the studies exploring the moderating role of serotonin transporter on the effect of environmental adversities over time, particularly during childhood and adolescence, which is when level of internalizing symptoms and prevalence of mood disorders change substantially. Environmental adversities will not include abuse and maltreatment that have been reviewed before (see Bellani et al. 2012) and child's broader social ecology that will be reviewed in the next section.

Interaction between specific forms of childhood maltreatment and the serotonin transporter gene (5-HTT) in recurrent depressive disorder

BACKGROUND

There is inconsistent evidence of interaction between stressful events and a serotonin transporter promoter polymorphism (5-HTTLPR) in depression. Recent studies have indicated that the moderating effect of 5-HTTLPR may be strongest when adverse experiences have occurred in childhood and the depressive symptoms persist over time. However, it is unknown whether this gene-environment interaction is present for recurrent depressive disorder and different forms of maltreatment. Therefore, patients with recurrent clinically diagnosed depression and controls screened for the absence of depression were utilised to examine the moderating effect of 5-HTTLPR on associations between specific forms of childhood adversity and recurrent depression.

METHOD

A sample of 227 recurrent unipolar depression cases and 228 never psychiatrically ill controls completed the Childhood Trauma Questionnaire to assess exposure to sexual, physical and emotional abuse, physical and emotional neglect in childhood. DNA extracted from blood or cheek swabs was genotyped for the short (s) and long (l) alleles of 5-HTTLPR.

RESULTS

All forms of childhood maltreatment were reported as more severe by cases than controls. There was no direct association between 5-HTTLPR and depression. Significant interactions with additive and recessive 5-HTTLPR genetic models were found for overall severity of maltreatment, sexual abuse and to a lesser degree for physical neglect, but not other maltreatment types.

LIMITATIONS

The cross-sectional design limits causal inference. Retrospective report of childhood adversity may have reduced the accuracy of the findings.

CONCLUSIONS

This study provides support for the role of interplay between 5-HTTLPR and a specific early environmental risk in recurrent depressive disorder.

Influence of genetic polymorphisms in the glutamatergic and GABAergic systems and their interactions with environmental stressors on antidepressant response

Aim: To investigate the role of genetic polymorphisms in glutamatergic and GABAergic genes and their interactions with environmental stressors in antidepressant response. Methods: A set of 114 SNPs of 34 glutamatergic and GABAergic genes, mainly in promoter and coding regions, were genotyped in 281 Chinese Han major depressive disorder patients. The 17-item Hamilton Depression Rating Scale was used to evaluate the symptom severity and therapeutic efficacy. Childhood Trauma Questionnaire and Life Events Scale were used for assessing early-onset and recent stressful life events, respectively. Results: The single SNPs rs1954787 (GRIK4), rs1992647 (GABRA6), rs10036156 (GABRP) and rs3810651 (GABRQ) were significantly associated with antidepressant response, as were haplotypes in GRIK4 and GABRP genes. A genetic interaction between rs11542313 (GAD1), rs13303344 (GABRD) and rs2256882 (GABRE) was identified as impacting therapeutic response. SNPs in GRIA3 demonstrated interactions with early-onset adverse events and recent negative life stress that influence treatment outcome. Conclusion: Genetic polymorphisms in the glutamatergic and GABAergic systems and certain genetic interactions, as well as gene–environment interactions, are associated with antidepressant response.

Original submitted 9 July 2012; Revision submitted 1 January 2013

Serotonin transporter length polymorphism, childhood maltreatment, and chronic depression: a specific gene-environment interaction

BACKGROUND

Key questions about the interaction between the serotonin transporter length polymorphism (5-HTTLPR) and stress in the etiology of depression remain unresolved. We test the hypotheses that the interaction is restricted to childhood maltreatment (as opposed to stressful events in adulthood), and leads to chronic depressive episodes (as opposed to any onset of depression), using gold-standard assessments of childhood maltreatment, severe life events, chronic depression, and new depressive onsets.

METHOD

In a risk-enriched sample of 273 unrelated women, childhood maltreatment was retrospectively assessed with the Childhood Experience of Care and Abuse (CECA) interview and 5-HTTLPR was genotyped. A subset of 220 women was followed prospectively for 12 months with life events assessed with the Life Events and Difficulties (LEDS) interview. Any chronic episode of depression (12 months or longer) during adulthood and onset of a major depressive episode during a 12-month follow-up were established with the Schedules for Clinical Assessment in Neuropsychiatry (SCAN) interview.

RESULTS

The short alleles of 5-HTTLPR moderated the relationship between childhood maltreatment and chronic depression in adulthood, reflected in a significant gene-environment interaction (RD = 0.226, 95% CI: 0.076-0.376, P = .0032). 5-HTTLPR did not moderate the effects of either childhood maltreatment or severe life events on new depressive onsets.

CONCLUSIONS

The short variant of the serotonin transporter gene specifically sensitizes to the effect of early-life experience of abuse or neglect on whether an adult depressive episode takes a chronic course. This interaction may be responsible for a substantial proportion of cases of chronic depression in the general population.