1 3313 97 HIPPOCAMPAL BDNF IN PHYSIOLOGICAL CONDITIONS AND SOCIAL ISOLATION. EXPOSURE OF AN ORGANISM TO CHRONIC PSYCHOSOCIAL STRESS MAY AFFECT BRAIN-DERIVED NEUROTROPHIC FACTOR (BDNF) EXPRESSION THAT HAS BEEN IMPLICATED IN THE ETIOLOGY OF PSYCHIATRIC DISORDERS, SUCH AS DEPRESSION. GIVEN THAT DEPRESSION IN HUMANS HAS BEEN LINKED WITH SOCIAL STRESS, THE CHRONIC SOCIAL STRESS PARADIGMS FOR MODELING PSYCHIATRIC DISORDERS IN ANIMALS HAVE THUS BEEN DEVELOPED. CHRONIC SOCIAL ISOLATION IN ANIMAL MODELS GENERALLY CAUSES CHANGES IN HYPOTHALAMIC-PITUITARY-ADRENAL AXIS FUNCTIONING, ASSOCIATED WITH ANXIETY- AND DEPRESSIVE-LIKE BEHAVIORS. ALSO, THIS CHRONIC STRESS CAUSES DOWNREGULATION OF BDNF PROTEIN AND MRNA IN THE HIPPOCAMPUS, A STRESS-SENSITIVE BRAIN REGION CLOSELY RELATED TO THE PATHOPHYSIOLOGY OF DEPRESSION. IN THIS REVIEW, WE DISCUSS THE CURRENT KNOWLEDGE REGARDING THE STRUCTURE, FUNCTION, INTRACELLULAR SIGNALING, INTER-INDIVIDUAL DIFFERENCES AND EPIGENETIC REGULATION OF BDNF IN BOTH PHYSIOLOGICAL CONDITIONS AND DEPRESSION AND CHANGES IN CORTICOSTERONE LEVELS, AS A MARKER OF STRESS RESPONSE. SINCE BDNF LEVELS ARE AGE DEPENDENT IN HUMANS AND RODENTS, THIS REVIEW WILL ALSO HIGHLIGHT THE EFFECTS OF ADOLESCENT AND ADULT CHRONIC SOCIAL ISOLATION MODELS OF BOTH GENDERS ON THE BDNF EXPRESSION. 2017 2 4642 36 NEURONAL PLASTICITY: A LINK BETWEEN STRESS AND MOOD DISORDERS. ALTHOUGH STRESS REPRESENTS THE MAJOR ENVIRONMENTAL ELEMENT OF SUSCEPTIBILITY FOR MOOD DISORDERS, THE RELATIONSHIP BETWEEN STRESS AND DISEASE REMAINS TO BE FULLY ESTABLISHED. IN THE PRESENT ARTICLE WE REVIEW THE EVIDENCE IN SUPPORT FOR A ROLE OF NEURONAL PLASTICITY, AND IN PARTICULAR OF NEUROTROPHIC FACTORS. EVEN THOUGH DECREASED LEVELS OF NOREPINEPHRINE AND SEROTONIN MAY UNDERLIE DEPRESSIVE SYMPTOMS, COMPELLING EVIDENCE NOW SUGGESTS THAT MOOD DISORDERS ARE CHARACTERIZED BY REDUCED NEURONAL PLASTICITY, WHICH CAN BE BROUGHT ABOUT BY EXPOSURE TO STRESS AT DIFFERENT STAGES OF LIFE. INDEED THE EXPRESSION OF NEUROTROPHIC MOLECULES, SUCH AS THE NEUROTROPHIN BDNF, IS REDUCED IN DEPRESSED SUBJECTS AS WELL AS IN EXPERIMENTAL ANIMALS EXPOSED TO ADVERSE EXPERIENCE AT EARLY STAGES OF LIFE OR AT ADULTHOOD. THESE CHANGES SHOW AN ANATOMICAL SPECIFICITY AND MIGHT BE SUSTAINED BY EPIGENETIC MECHANISMS. PHARMACOLOGICAL INTERVENTION MAY NORMALIZE SUCH DEFECTS AND IMPROVE NEURONAL FUNCTION THROUGH THE MODULATION OF THE SAME FACTORS THAT ARE DEFECTIVE IN DEPRESSION. SEVERAL STUDIES HAVE DEMONSTRATED THAT CHRONIC, BUT NOT ACUTE, ANTIDEPRESSANT TREATMENT INCREASES THE EXPRESSION OF BDNF AND MAY ENHANCE ITS LOCALIZATION AT SYNAPTIC LEVEL. ANTIDEPRESSANT TREATMENT CAN NORMALIZE DEFICITS IN NEUROTROPHIN EXPRESSION PRODUCED BY CHRONIC STRESS PARADIGMS, BUT MAY ALSO ALTER THE MODULATION OF BDNF UNDER ACUTE STRESSFUL CONDITIONS. IN SUMMARY, THERE IS GOOD AGREEMENT IN CONSIDERING NEURONAL PLASTICITY, AND THE EXPRESSION OF KEY PROTEINS SUCH AS THE NEUROTROPHIN BDNF, AS A CENTRAL PLAYER FOR THE EFFECTS OF STRESS ON BRAIN FUNCTION AND ITS IMPLICATION FOR PSYCHOPATHOLOGY. ACCORDINGLY, EFFECTIVE TREATMENTS SHOULD NOT LIMIT THEIR EFFECTS TO THE CONTROL OF NEUROTRANSMITTER AND HORMONAL DYSFUNCTIONS, BUT SHOULD BE ABLE TO NORMALIZE DEFECTIVE MECHANISMS THAT SUSTAIN THE IMPAIRMENT OF NEURONAL PLASTICITY. 2009 3 6174 44 THE HIPPOCAMPUS, NEUROTROPHIC FACTORS AND DEPRESSION: POSSIBLE IMPLICATIONS FOR THE PHARMACOTHERAPY OF DEPRESSION. DEPRESSION IS A PREVALENT, HIGHLY DEBILITATING MENTAL DISORDER AFFECTING UP TO 15% OF THE POPULATION AT LEAST ONCE IN THEIR LIFETIME, WITH HUGE COSTS FOR SOCIETY. NEUROBIOLOGICAL MECHANISMS OF DEPRESSION ARE STILL NOT WELL KNOWN, ALTHOUGH THERE IS CONSENSUS ABOUT INTERPLAY BETWEEN GENETIC AND ENVIRONMENTAL FACTORS. ANTIDEPRESSANT MEDICATIONS ARE FREQUENTLY USED IN DEPRESSION, BUT AT LEAST 50% OF PATIENTS ARE POOR RESPONDERS, EVEN TO MORE RECENTLY DISCOVERED MEDICATIONS. FURTHERMORE, CLINICAL RESPONSE ONLY OCCURS FOLLOWING WEEKS TO MONTHS OF TREATMENT AND ONLY CHRONIC TREATMENT IS EFFECTIVE, SUGGESTING THAT ACTIONS BEYOND THE RAPIDLY OCCURRING EFFECT OF ENHANCING MONOAMINERGIC SYSTEMS, SUCH AS ADAPTATION OF THESE SYSTEMS, ARE RESPONSIBLE FOR THE EFFECTS OF ANTIDEPRESSANTS. RECENT STUDIES INDICATE THAT AN IMPAIRMENT OF SYNAPTIC PLASTICITY (NEUROGENESIS, AXON BRANCHING, DENDRITOGENESIS AND SYNAPTOGENESIS) IN SPECIFIC AREAS OF THE CNS, PARTICULARLY THE HIPPOCAMPUS, MAY BE A CORE FACTOR IN THE PATHOPHYSIOLOGY OF DEPRESSION. THE ABNORMAL NEURAL PLASTICITY MAY BE RELATED TO ALTERATIONS IN THE LEVELS OF NEUROTROPHIC FACTORS, NAMELY BRAIN-DERIVED NEUROTROPHIC FACTOR (BDNF), WHICH PLAY A CENTRAL ROLE IN PLASTICITY. AS BDNF IS REPRESSED BY STRESS, EPIGENETIC REGULATION OF THE BDNF GENE MAY PLAY AN IMPORTANT ROLE IN DEPRESSION. THE HIPPOCAMPUS IS SMALLER IN DEPRESSED PATIENTS, ALTHOUGH IT IS UNCLEAR WHETHER SMALLER SIZE IS A CONSEQUENCE OF DEPRESSION OR A PRE-EXISTING, VULNERABILITY MARKER FOR DEPRESSION. ENVIRONMENTAL STRESSORS TRIGGERING ACTIVATION OF THE HYPOTHALAMIC-PITUITARY-ADRENAL AXIS CAUSE THE BRAIN TO BE EXPOSED TO CORTICOSTEROIDS, AFFECTING NEUROBEHAVIOURAL FUNCTIONS WITH A STRONG DOWNREGULATION OF HIPPOCAMPAL NEUROGENESIS, AND ARE A MAJOR RISK FACTOR FOR DEPRESSION. ANTIDEPRESSANT TREATMENT INCREASES BDNF LEVELS, STIMULATES NEUROGENESIS AND REVERSES THE INHIBITORY EFFECTS OF STRESS, BUT THIS EFFECT IS EVIDENT ONLY AFTER 3-4 WEEKS OF ADMINISTRATION, THE TIME COURSE FOR MATURATION OF NEW NEURONS. THE ABLATION OF HIPPOCAMPAL NEUROGENESIS BLOCKS THE BEHAVIOURAL EFFECTS OF ANTIDEPRESSANTS IN ANIMAL MODELS. THE ABOVE FINDINGS SUGGEST NEW POSSIBLE TARGETS FOR THE PHARMACOTHERAPY OF DEPRESSION SUCH AS NEUROTROPHIC FACTORS, THEIR RECEPTORS AND RELATED INTRACELLULAR SIGNALLING CASCADES; AGENTS COUNTERACTING THE EFFECTS OF STRESS ON HIPPOCAMPAL NEUROGENESIS (INCLUDING ANTAGONISTS OF CORTICOSTEROIDS, INFLAMMATORY CYTOKINES AND THEIR RECEPTORS); AND AGENTS FACILITATING THE ACTIVATION OF GENE EXPRESSION AND INCREASING THE TRANSCRIPTION OF NEUROTROPHINS IN THE BRAIN. 2011 4 1981 35 EPIGENETIC ALTERATIONS IN DNA AND HISTONE MODIFICATIONS CAUSED BY DEPRESSION AND ANTIDEPRESSANT DRUGS: LESSONS FROM THE RODENT MODELS. EPIGENETIC MODIFICATIONS REGULATE CHROMATIN FOLDING AND FUNCTION. EPIGENETIC MECHANISMS REGULATE TRANSCRIPTION MEDIATING EFFECTS OF VARIOUS STIMULI ON GENE EXPRESSION. THESE MECHANISMS ARE INVOLVED IN TRANSCRIPTIONAL CONTROL IN VARIOUS PHYSIOLOGICAL AND PATHOLOGICAL CONDITIONS INCLUDING NEUROPSYCHIATRIC DISORDERS AND BEHAVIORAL ABNORMALITIES SUCH AS DEPRESSION. IN RODENTS, EXPOSURE TO CHRONIC SOCIAL STRESS WAS SHOWN TO INDUCE BEHAVIORAL IMPAIRMENTS AND MEMORY/LEARNING DEFICITS THAT RESEMBLE DEPRESSIVE-LIKE PHENOTYPE IN HUMANS. THE RODENT MODELS OF CHRONIC STRESS WERE WIDELY USED TO STUDY MOLECULAR MECHANISMS OF DEPRESSION. IN THESE MODELS, EARLY EXPOSURE TO CHRONIC STRESS SUCH AS PRENATAL OR POSTNATAL STRESS INDUCES LONG-TERM HYPERACTIVE STRESS RESPONSES, BEHAVIORAL ABNORMALITIES, AND FUNCTIONAL IMPAIRMENTS IN BRAIN FUNCTION THAT PERSIST IN ADULTHOOD. FURTHERMORE, THESE ALTERATIONS CAN BE TRANSMITTED TO OFFSPRING OF CHRONICALLY STRESSED ANIMALS ACROSS SEVERAL GENERATIONS. MOLECULAR STUDIES IN ANIMAL MODELS SHOWED THAT CHRONIC STRESS INDUCES STABLE EPIGENETIC CHANGES IN SPECIFIC BRAIN REGIONS, PRIMARILY IN THE LIMBIC SYSTEM. THESE CHANGES LEAD TO LONG-LASTING ABNORMALITIES IN BEHAVIOR THAT PERSIST IN ADULTHOOD AND CAN BE TRANSMITTED TO OFFSPRING. TREATMENT WITH EPIGENETICALLY ACTIVE ANTIDEPRESSANTS DISRUPTS THE ABNORMAL STRESS-INDUCED EPIGENETIC PROGRAMMING AND PROVIDES EPIGENETIC PATTERNS THAT RESEMBLE EPIGENETIC BACKGROUND OF STRESS RESILIENT INDIVIDUALS. 2017 5 291 32 AGING AND STRESS: PAST HYPOTHESES, PRESENT APPROACHES AND PERSPECTIVES. BRAIN AGING HAS BEEN SUGGESTED TO BE CONDITIONED BY AN EXCESSIVE GLUCOCORTIOID SECRETION LEADING TO DAMAGES ON BRAIN AREAS INVOLVED NOT ONLY IN COGNITIVE AND EMOTIONAL PROCESSES BUT ALSO IN THE CONTROL OF THE ACTIVITY OF THE HYPOTHALAMIC-PITUITARY ADRENAL AXIS. THIS REVIEW DESCRIBES SOME OF THE HYPOTHESIS THAT TRY TO EXPLAIN THE RELATION BETWEEN THE DYSREGULATION OF THE STRESS RESPONSE AND BRAIN AGING, FOCUSING ON CORTICOSTERONE BUT ALSO ON NEUROTRANSMISSION IN THE HIPPOCAMPUS, THE PREFRONTAL CORTEX AND THE AMYGDALA. MOREOVER, DIFFERENT MOLECULAR FACTORS CAN ACCOUNT FOR AN ENHANCED VULNERABILITY OF THE AGED BRAIN TO STRESS EXPOSURE, SPECIALLY FOR RESILIENCE. AMONG THEM, GOOD CANDIDATES COULD BE THOSE MECHANISMS DETERMINING THE LEVELS OF CORTICOSTERONE IN THE BRAIN, SEVERAL MOLECULES DOWNSTREAM GLUCOCORTICOID RECEPTOR ACTIVATION (IE: HEAT SHOCK PROTEINS, BAG-1) OR EVEN THE EPIGENETIC PROGRAMMING OF THE HPA AXIS IN EARLY STAGES. IN CONCLUSION, GENETIC AND ENVIRONMENTAL FACTORS (EARLY LIFE STRESS, CHRONIC STRESS DURING ADULTHOOD) CAN PRODUCE AN ENHANCED VULNERABILITY AND A REDUCED RESILIENCE OF THE BRAIN TO SUBSEQUENT STRESS EXPOSURES OR TO METABOLIC CHALLENGES LEADING, IN TURN, TO AN UNSUCCESSFUL AGING OF THE BRAIN. HOWEVER, RESULTS OBTAINED WITH THE USE OF THE ENVIRONMENTAL ENRICHMENT MODEL IN ANIMALS, ADDED TO SEVERAL RESULTS IN HUMANS ALSO DESCRIBED IN THIS REVIEW SUGGEST THAT POSITIVE ENVIRONMENTAL FACTORS (COGNITIVE-DEMANDING TASKS OR PHYSICAL EXERCISE) CAN HELP TO MAINTAIN NEURONAL PLASTICITY DURING AGING AND TO PROTECT THE BRAIN AGAINST THE DAMAGING EFFECTS OF STRESS EXPOSURE. 2011 6 6228 29 THE LINKS BETWEEN STRESS AND DEPRESSION: PSYCHONEUROENDOCRINOLOGICAL, GENETIC, AND ENVIRONMENTAL INTERACTIONS. THE ROLE OF STRESS IN THE ORIGIN AND DEVELOPMENT OF DEPRESSION MAY BE CONCEIVED AS THE RESULT OF MULTIPLE CONVERGING FACTORS, INCLUDING THE CHRONIC EFFECT OF ENVIRONMENTAL STRESSORS AND THE LONG-LASTING EFFECTS OF STRESSFUL EXPERIENCES DURING CHILDHOOD, ALL OF WHICH MAY INDUCE PERSISTENT HYPERACTIVITY OF THE HYPOTHALAMIC-PITUITARY-ADRENAL AXIS. THESE CHANGES, INCLUDING INCREASED AVAILABILITY OF CORTICOTROPIN-RELEASING FACTOR AND CORTISOL, ARE ALSO ASSOCIATED WITH HYPERACTIVITY OF THE AMYGDALA, HYPOACTIVITY OF THE HIPPOCAMPUS, AND DECREASED SEROTONERGIC NEUROTRANSMISSION, WHICH TOGETHER RESULT IN INCREASED VULNERABILITY TO STRESS. THE ROLE OF OTHER MONOAMINERGIC NEUROTRANSMITTERS, GENETIC POLYMORPHISMS, EPIGENETIC MECHANISMS, INFLAMMATORY PROCESSES, AND ALTERED COGNITIVE PROCESSING HAS ALSO BEEN CONSIDERED IN THE DEVELOPMENT OF A COMPREHENSIVE MODEL OF THE INTERACTIONS BETWEEN DIFFERENT FACTORS OF VULNERABILITY. FURTHER UNDERSTANDING OF THE UNDERLYING MECHANISMS THAT LINK THESE FACTORS MAY CONTRIBUTE SIGNIFICANTLY TO THE DEVELOPMENT OF MORE EFFECTIVE TREATMENTS AND PREVENTIVE STRATEGIES IN THE INTERFACE BETWEEN STRESS AND MOOD DISORDERS. 2016 7 235 32 ADDING FUEL TO THE FIRE: THE IMPACT OF STRESS ON THE AGEING BRAIN. BOTH AGEING AND CHRONIC STRESS ARE ASSOCIATED WITH ALTERED BRAIN PLASTICITY, DYSREGULATION OF THE IMMUNE SYSTEM, AND AN INCREASED RISK OF DEVELOPING BRAIN DISORDERS; ALL OF WHICH HAVE CONSEQUENCES FOR COGNITIVE AND EMOTIONAL PROCESSING. HERE WE EXAMINE THE SIMILARITIES BETWEEN BEHAVIOURAL CHANGES DURING AGEING AND STRESS ALTERED BEHAVIOURS (ANXIETY, DEPRESSIVE-LIKE BEHAVIOUR, COGNITION, AND SOCIABILITY) IN RODENTS AND HUMANS. THE MOLECULAR MECHANISMS HYPOTHESISED TO MEDIATE AGE-RELATED CHANGES IN BRAIN FUNCTION INCLUDING DYSFUNCTION OF THE HYPOTHALAMIC-PITUITARY-ADRENAL (HPA) AXIS, DYSREGULATION OF NEUROTRANSMISSION AND NEUROTROPHIC FACTOR SIGNALLING, INCREASED INFLAMMATORY STATE, GENETIC AND EPIGENETIC CHANGES, OXIDATIVE STRESS, METABOLIC CHANGES, AND CHANGES IN THE MICROBIOTA-GUT-BRAIN AXIS ARE DISCUSSED. FINALLY, WE EXPLORE HOW THE ALREADY STRESSED AGED BRAIN PSYCHOLOGICALLY AND PHYSIOLOGICALLY RESPONDS TO EXTERNAL STRESSORS. 2015 8 2269 42 EPIGENETIC PROGRAMMING OF THE NEUROENDOCRINE STRESS RESPONSE BY ADULT LIFE STRESS. THE HYPOTHALAMIC-PITUITARY-ADRENAL (HPA) AXIS IS CRITICALLY INVOLVED IN THE NEUROENDOCRINE REGULATION OF STRESS ADAPTATION, AND THE RESTORATION OF HOMEOSTASIS FOLLOWING STRESS EXPOSURE. DYSREGULATION OF THIS AXIS IS ASSOCIATED WITH STRESS-RELATED PATHOLOGIES LIKE MAJOR DEPRESSIVE DISORDER, POST-TRAUMATIC STRESS DISORDER, PANIC DISORDER AND CHRONIC ANXIETY. IT HAS LONG BEEN UNDERSTOOD THAT STRESS DURING EARLY LIFE CAN HAVE A SIGNIFICANT LASTING INFLUENCE ON THE DEVELOPMENT OF THE NEUROENDOCRINE SYSTEM AND ITS NEURAL REGULATORS, PARTIALLY BY MODIFYING EPIGENETIC REGULATION OF GENE EXPRESSION, WITH IMPLICATIONS FOR HEALTH AND WELL-BEING IN LATER LIFE. EVIDENCE IS ACCUMULATING THAT EPIGENETIC PLASTICITY ALSO EXTENDS TO ADULTHOOD, PROPOSING IT AS A MECHANISM BY WHICH PSYCHOLOGICAL TRAUMA LATER IN LIFE CAN LONG-LASTINGLY AFFECT HPA AXIS FUNCTION, BRAIN PLASTICITY, NEURONAL FUNCTION AND BEHAVIOURAL ADAPTATION TO NEUROPSYCHOLOGICAL STRESS. FURTHER CORROBORATING THIS CLAIM IS THE PHENOMENON THAT THESE EPIGENETIC CHANGES CORRELATE WITH THE BEHAVIOURAL CONSEQUENCES OF TRAUMA EXPOSURE. THEREBY, EPIGENETIC MODIFICATIONS PROVIDE A PUTATIVE MOLECULAR MECHANISM BY WHICH THE BEHAVIOURAL PHENOTYPE AND TRANSCRIPTIONAL/TRANSLATIONAL POTENTIAL OF GENES INVOLVED IN HPA AXIS REGULATION CAN CHANGE DRASTICALLY IN RESPONSE TO ENVIRONMENTAL CHALLENGES, AND APPEAR AN IMPORTANT TARGET FOR TREATMENT OF STRESS-RELATED DISORDERS. HOWEVER, IMPROVED INSIGHT IS REQUIRED TO INCREASE THEIR THERAPEUTIC (DRUG) POTENTIAL. HERE, WE PROVIDE AN OVERVIEW OF THE GROWING BODY OF LITERATURE DESCRIBING THE EPIGENETIC MODULATION OF THE (PRIMARILY NEUROENDOCRINE) STRESS RESPONSE AS A CONSEQUENCE OF ADULT LIFE STRESS AND INTERPRET THE IMPLICATIONS FOR, AND THE CHALLENGES INVOLVED IN APPLYING THIS KNOWLEDGE TO, THE IDENTIFICATION AND TREATMENT OF STRESS-RELATED PSYCHIATRIC DISORDERS. 2017 9 2445 23 EPIGENETIC STATUS OF GDNF IN THE VENTRAL STRIATUM DETERMINES SUSCEPTIBILITY AND ADAPTATION TO DAILY STRESSFUL EVENTS. STRESSFUL EVENTS DURING ADULTHOOD ARE POTENT ADVERSE ENVIRONMENTAL FACTORS THAT CAN PREDISPOSE INDIVIDUALS TO PSYCHIATRIC DISORDERS, INCLUDING DEPRESSION; HOWEVER, MANY INDIVIDUALS EXPOSED TO STRESSFUL EVENTS CAN ADAPT AND FUNCTION NORMALLY. WHILE STRESS VULNERABILITY MAY INFLUENCE DEPRESSION, THE MOLECULAR MECHANISMS UNDERLYING THE SUSCEPTIBILITY AND ADAPTATION TO CHRONIC STRESS WITHIN THE BRAIN ARE POORLY UNDERSTOOD. IN THIS STUDY, TWO GENETICALLY DISTINCT MOUSE STRAINS THAT EXHIBIT DIFFERENT BEHAVIORAL RESPONSES TO CHRONIC STRESS WERE USED TO DEMONSTRATE HOW THE DIFFERENTIAL EPIGENETIC STATUS OF THE GLIAL CELL-DERIVED NEUROTROPHIC FACTOR (GDNF) GENE IN THE VENTRAL STRIATUM MODULATES SUSCEPTIBILITY AND ADAPTATION TO CHRONIC STRESS. OUR RESULTS SUGGEST THAT THE HISTONE MODIFICATIONS AND DNA METHYLATION OF THE GDNF PROMOTER HAVE CRUCIAL ROLES IN THE CONTROL OF BEHAVIORAL RESPONSES TO CHRONIC STRESS. OUR DATA PROVIDE INSIGHTS INTO THESE MECHANISMS, SUGGESTING THAT EPIGENETIC MODIFICATIONS OF GDNF, ALONG WITH GENETIC AND ENVIRONMENTAL FACTORS, CONTRIBUTE TO BEHAVIORAL RESPONSES TO STRESS. 2011 10 2159 35 EPIGENETIC MECHANISMS IMPACTED BY CHRONIC STRESS ACROSS THE RODENT LIFESPAN. EXPOSURES TO STRESS AT ALL STAGES OF DEVELOPMENT CAN LEAD TO LONG-TERM BEHAVIOURAL EFFECTS, IN PART THROUGH CHANGES IN THE EPIGENOME. THIS REVIEW DESCRIBES RODENT RESEARCH SUGGESTING THAT STRESS IN PRENATAL, POSTNATAL, ADOLESCENT AND ADULT STAGES LEADS TO LONG-TERM CHANGES IN EPIGENETIC REGULATION IN THE BRAIN WHICH HAVE CAUSAL IMPACTS ON RODENT BEHAVIOUR. WE FOCUS ON STRESS-INDUCED EPIGENETIC CHANGES THAT HAVE BEEN LINKED TO BEHAVIOURAL DEFICITS INCLUDING POOR LEARNING AND MEMORY, AND INCREASED ANXIETY-LIKE AND DEPRESSIVE-LIKE BEHAVIOURS. INTERESTINGLY, ASPECTS OF THESE STRESS-INDUCED BEHAVIOURAL CHANGES CAN BE TRANSMITTED TO OFFSPRING ACROSS SEVERAL GENERATIONS, A PHENOMENON THAT HAS BEEN PROPOSED TO RESULT VIA EPIGENETIC MECHANISMS IN THE GERMLINE. HERE, WE ALSO DISCUSS EVIDENCE FOR THE DIFFERENTIAL IMPACT OF STRESS ON THE EPIGENOME IN MALES AND FEMALES, CONSCIOUS OF THE FACT THAT THE MAJORITY OF PUBLISHED STUDIES HAVE ONLY INVESTIGATED MALES. THIS HAS LED TO A LIMITED PICTURE OF THE EPIGENETIC IMPACT OF STRESS, HIGHLIGHTING THE NEED FOR FUTURE STUDIES TO INVESTIGATE FEMALES AS WELL AS MALES. 2022 11 248 35 ADVANCE IN STRESS FOR DEPRESSIVE DISORDER. STRESS IS AN ADAPTIVE RESPONSE TO ENVIRONMENT AVERSIVE STIMULI AND A COMMON LIFE EXPERIENCE OF ONE'S DAILY LIFE. CHRONIC OR EXCESSIVE STRESS ESPECIALLY THAT HAPPENED IN EARLY LIFE IS FOUND TO BE DELETERIOUS TO INDIVIDUAL'S PHYSICAL AND MENTAL HEALTH, WHICH IS HIGHLY RELATED TO DEPRESSIVE DISORDERS ONSET. STRESSFUL LIFE EVENTS ARE CONSISTENTLY CONSIDERED TO BE THE HIGH-RISK FACTORS OF ENVIRONMENT FOR PREDISPOSING DEPRESSIVE DISORDERS. IN LINKING STRESSFUL LIFE EVENTS WITH DEPRESSIVE DISORDER ONSET, DYSREGULATED HPA AXIS ACTIVITY IS SUPPOSED TO PLAY AN IMPORTANT ROLE IN MEDIATING AVERSIVE IMPACTS OF LIFE STRESS ON BRAIN STRUCTURE AND FUNCTION. INCREASING EVIDENCE HAVE INDICATED THE STRONG ASSOCIATION OF STRESS, ESPECIALLY THE CHRONIC STRESS AND EARLY LIFE STRESS, WITH DEPRESSIVE DISORDERS DEVELOPMENT, WHILE THE ASSOCIATION OF STRESS WITH DEPRESSION IS MODERATED BY GENETIC RISK FACTORS, INCLUDING POLYMORPHISM OF SERT, BDNF, GR, FKBP5, MR, AND CRHR1. MEANWHILE, STRESSFUL LIFE EXPERIENCE PARTICULARLY EARLY LIFE STRESS WILL EXERT EPIGENETIC MODIFICATION IN THESE RISK GENES VIA DNA METHYLATION AND MIRNA REGULATION TO GENERATE LONG-LASTING EFFECTS ON THESE GENES EXPRESSION, WHICH IN TURN CAUSE BRAIN STRUCTURAL AND FUNCTIONAL ALTERATION, AND FINALLY INCREASE THE VULNERABILITY TO DEPRESSIVE DISORDERS. THEREFORE, THE INTERACTION OF ENVIRONMENT WITH GENE, IN WHICH STRESSFUL LIFE EXPOSURE INTERPLAY WITH GENETIC RISK FACTORS AND EPIGENETIC MODIFICATION, IS ESSENTIAL IN PREDICTING DEPRESSIVE DISORDERS DEVELOPMENT. AS THE MEDIATOR OF ENVIRONMENTAL RISK FACTORS, STRESS WILL FUNCTION TOGETHER WITH GENETIC AND EPIGENETIC MECHANISM TO INFLUENCE BRAIN STRUCTURE AND FUNCTION, PHYSIOLOGY AND PSYCHOLOGY, AND FINALLY THE VULNERABILITY TO DEPRESSIVE DISORDERS. 2019 12 2021 28 EPIGENETIC CHANGES ASSOCIATED WITH DIFFERENT TYPES OF STRESSORS AND SUICIDE. STRESS IS ASSOCIATED WITH VARIOUS EPIGENETIC CHANGES. SOME STRESS-INDUCED EPIGENETIC CHANGES ARE HIGHLY DYNAMIC, WHEREAS OTHERS ARE ASSOCIATED WITH LASTING MARKS ON THE EPIGENOME. IN OUR STUDY, A COMPREHENSIVE NARRATIVE REVIEW OF THE LITERATURE WAS PERFORMED BY INVESTIGATING THE EPIGENETIC CHANGES THAT OCCUR WITH ACUTE STRESS, CHRONIC STRESS, EARLY CHILDHOOD STRESS, AND TRAUMATIC STRESS EXPOSURES, ALONG WITH EXAMINING THOSE OBSERVED IN POST-MORTEM BRAINS OR BLOOD SAMPLES OF SUICIDE COMPLETERS AND ATTEMPTERS. IN ADDITION, THE TRANSGENERATIONAL EFFECTS OF THESE CHANGES ARE REPORTED. FOR ALL TYPES OF STRESS STUDIES EXAMINED, THE GENES NR3C1, OXTR, SLC6A4, AND BDNF REPRODUCIBLY SHOWED EPIGENETIC CHANGES, WITH SOME MODIFICATIONS OBSERVED TO BE PASSED DOWN TO SUBSEQUENT GENERATIONS FOLLOWING STRESS EXPOSURES. THE AFOREMENTIONED GENES ARE KNOWN TO BE INVOLVED IN NEURONAL DEVELOPMENT AND HORMONAL REGULATION AND ARE ALL ASSOCIATED WITH SUSCEPTIBILITY TO MENTAL HEALTH DISORDERS INCLUDING DEPRESSION, ANXIETY, PERSONALITY DISORDERS, AND PTSD (POST-TRAUMATIC STRESS DISORDER). FURTHER RESEARCH IS WARRANTED IN ORDER TO DETERMINE THE SCOPE OF EPIGENETIC ACTIONABLE TARGETS IN INDIVIDUALS SUFFERING FROM THE LONG-LASTING EFFECTS OF STRESSFUL EXPERIENCES. 2023 13 1790 33 EFFECT OF CHRONIC MILD STRESS ON HIPPOCAMPAL TRANSCRIPTOME IN MICE SELECTED FOR HIGH AND LOW STRESS-INDUCED ANALGESIA AND DISPLAYING DIFFERENT EMOTIONAL BEHAVIORS. THERE IS INCREASING EVIDENCE THAT MOOD DISORDERS MAY DERIVE FROM THE IMPACT OF ENVIRONMENTAL PRESSURE ON GENETICALLY SUSCEPTIBLE INDIVIDUALS. STRESS-INDUCED HIPPOCAMPAL PLASTICITY HAS BEEN IMPLICATED IN DEPRESSION. WE STUDIED HIPPOCAMPAL TRANSCRIPTOMES IN STRAINS OF MICE THAT DISPLAY HIGH (HA) AND LOW (LA) SWIM STRESS-INDUCED ANALGESIA AND THAT DIFFER IN EMOTIONAL BEHAVIORS AND RESPONSES TO DIFFERENT CLASSES OF ANTIDEPRESSANTS. CHRONIC MILD STRESS (CMS) AFFECTED EXPRESSION OF A NUMBER OF GENES COMMON FOR BOTH STRAINS. CMS ALSO PRODUCED STRAIN SPECIFIC CHANGES IN EXPRESSION SUGGESTING THAT HIPPOCAMPAL RESPONSES TO STRESS DEPEND ON GENOTYPE. CONSIDERABLY LARGER NUMBER OF GENES, BIOLOGICAL PROCESSES, MOLECULAR FUNCTIONS, BIOCHEMICAL PATHWAYS, AND GENE NETWORKS WERE AFFECTED BY CMS IN LA THAN IN HA MICE. THE RESULTS SUGGEST THAT POTENTIAL DRUG TARGETS AGAINST DETRIMENTAL EFFECTS OF STRESS INCLUDE GLUTAMATE TRANSPORTERS, AND CHOLINERGIC, CHOLECYSTOKININ (CCK), GLUCOCORTICOIDS, AND THYROID HORMONES RECEPTORS. FURTHERMORE, SOME BIOLOGICAL PROCESSES EVOKED BY STRESS AND DIFFERENT BETWEEN THE STRAINS, SUCH AS APOPTOSIS, NEUROGENESIS AND CHROMATIN MODIFICATIONS, MAY BE RESPONSIBLE FOR THE LONG-TERM, IRREVERSIBLE EFFECTS OF STRESS AND SUGGEST A ROLE FOR EPIGENETIC REGULATION OF MOOD RELATED STRESS RESPONSES. 2011 14 110 29 A ROLE FOR ACTIVITY-DEPENDENT EPIGENETICS IN THE DEVELOPMENT AND TREATMENT OF MAJOR DEPRESSIVE DISORDER. CHRONIC STRESSORS, DURING DEVELOPMENTAL SENSITIVE PERIODS AND BEYOND, CONTRIBUTE TO THE RISK OF DEVELOPING PSYCHIATRIC CONDITIONS, INCLUDING MAJOR DEPRESSIVE DISORDER (MDD). EPIGENETIC MECHANISMS INCLUDING DNA METHYLATION AND HISTONE MODIFICATIONS, AT KEY STRESS RESPONSE AND NEUROTROPHIN GENES, ARE INCREASINGLY IMPLICATED IN MEDIATING THIS RISK. ALTHOUGH THE EXACT MECHANISMS THROUGH WHICH STRESSFUL ENVIRONMENTAL STIMULI ALTER THE EPIGENOME ARE STILL UNCLEAR, RESEARCH FROM THE LEARNING AND MEMORY FIELDS INDICATES THAT EPIGENOMIC MARKS CAN BE ALTERED, AT LEAST IN PART, THROUGH CALCIUM-DEPENDENT SIGNALING CASCADES IN DIRECT RESPONSE TO NEURONAL ACTIVITY. IN THIS REVIEW, WE HIGHLIGHT KEY FINDINGS FROM THE STRESS, MDD, AND LEARNING AND MEMORY FIELDS TO PROPOSE A MODEL WHERE STRESS REGULATES DOWNSTREAM CELLULAR FUNCTIONING THROUGH ACTIVITY-DEPENDENT EPIGENETIC CHANGES. FURTHERMORE, WE SUGGEST THAT BOTH TYPICAL AND NOVEL ANTIDEPRESSANT TREATMENTS MAY EXERT POSITIVE INFLUENCE THROUGH SIMILAR, ACTIVITY-DEPENDENT PATHWAYS. 2018 15 3151 33 GLUCOCORTICOIDS, EPIGENETIC CONTROL AND STRESS RESILIENCE. GLUCOCORTICOID HORMONES PLAY A PIVOTAL ROLE IN THE RESPONSE TO STRESSFUL CHALLENGES. THE SURGE IN GLUCOCORTICOID HORMONE SECRETION AFTER STRESS NEEDS TO BE TIGHTLY CONTROLLED WITH CHARACTERISTICS LIKE PEAK HEIGHT, CURVATURE AND DURATION DEPENDING ON THE NATURE AND SEVERITY OF THE CHALLENGE. THIS IS IMPORTANT AS CHRONIC HYPER- OR HYPO-RESPONSES ARE DETRIMENTAL TO HEALTH DUE TO INCREASING THE RISK FOR DEVELOPING A STRESS-RELATED MENTAL DISORDER. PROPER GLUCOCORTICOID RESPONSES TO STRESS ARE CRITICAL FOR ADAPTATION. THEREFORE, THE TIGHT CONTROL OF BASELINE AND STRESS-EVOKED GLUCOCORTICOID SECRETION ARE IMPORTANT CONSTITUENTS OF AN ORGANISM'S RESILIENCE. HERE, WE ADDRESS A NUMBER OF MECHANISMS THAT ILLUSTRATE THE MULTITUDE AND COMPLEXITY OF MEASURES SAFEGUARDING THE CONTROL OF GLUCOCORTICOID FUNCTION. THESE MECHANISMS INCLUDE THE CONTROL OF MINERALOCORTICOID (MR) AND GLUCOCORTICOID RECEPTOR (GR) OCCUPANCY AND CONCENTRATION, THE DYNAMIC CONTROL OF FREE GLUCOCORTICOID HORMONE AVAILABILITY BY CORTICOSTEROID-BINDING GLOBULIN (CBG), AND THE CONTROL EXERTED BY GLUCOCORTICOIDS AT THE SIGNALING, EPIGENETIC AND GENOMIC LEVEL ON GENE TRANSCRIPTIONAL RESPONSES TO STRESS. WE REVIEW THE BENEFICIAL EFFECTS OF REGULAR EXERCISE ON HPA AXIS AND SLEEP PHYSIOLOGY, AND COGNITIVE AND ANXIETY-RELATED BEHAVIOR. FURTHERMORE, WE DESCRIBE THAT, POSSIBLY THROUGH CHANGES IN THE GABAERGIC SYSTEM, EXERCISE REDUCES THE IMPACT OF STRESS ON A SIGNALING PATHWAY SPECIFICALLY IN THE DENTATE GYRUS THAT IS STRONGLY IMPLICATED IN THE BEHAVIORAL RESPONSE TO THAT STRESSOR. THESE OBSERVATIONS UNDERLINE THE IMPACT OF LIFE STYLE ON STRESS RESILIENCE. FINALLY, WE ADDRESS HOW SINGLE NUCLEOTIDE POLYMORPHISMS (SNPS) AFFECTING GLUCOCORTICOID ACTION CAN COMPROMISE STRESS RESILIENCE, WHICH BECOMES MOST APPARENT UNDER CONDITIONS OF CHILDHOOD ABUSE. 2015 16 534 35 ASTROGLIA IN THE VULNERABILITY TO AND MAINTENANCE OF STRESS-MEDIATED NEUROPATHOLOGY AND DEPRESSION. SIGNIFICANT STRESS EXPOSURE AND PSYCHIATRIC DEPRESSION ARE ASSOCIATED WITH MORPHOLOGICAL, BIOCHEMICAL, AND PHYSIOLOGICAL DISTURBANCES OF ASTROCYTES IN SPECIFIC BRAIN REGIONS RELEVANT TO THE PATHOPHYSIOLOGY OF THOSE DISORDERS, SUGGESTING THAT ASTROCYTES ARE INVOLVED IN THE MECHANISMS UNDERLYING THE VULNERABILITY TO OR MAINTENANCE OF STRESS-RELATED NEUROPATHOLOGY AND DEPRESSION. TO UNDERSTAND THOSE MECHANISMS A VARIETY OF STUDIES HAVE PROBED THE EFFECT OF VARIOUS MODALITIES OF STRESS EXPOSURE ON THE METABOLISM, GENE EXPRESSION AND PLASTICITY OF ASTROCYTES. THESE STUDIES HAVE UNCOVERED THE PARTICIPATION OF VARIOUS CELLULAR PATHWAYS, SUCH AS THOSE FOR INTRACELLULAR CALCIUM REGULATION, NEUROIMMUNE RESPONSES, EXTRACELLULAR IONIC REGULATION, GAP JUNCTIONS-BASED CELLULAR COMMUNICATION, AND REGULATION OF NEUROTRANSMITTER AND GLIOTRANSMITTER RELEASE AND UPTAKE. MORE RECENTLY EPIGENETIC MODIFICATIONS RESULTING FROM EXPOSURE TO CHRONIC FORMS OF STRESS OR TO EARLY LIFE ADVERSITY HAVE BEEN SUGGESTED TO AFFECT NOT ONLY NEURONAL MECHANISMS BUT ALSO GENE EXPRESSION AND PHYSIOLOGY OF ASTROCYTES AND OTHER GLIAL CELLS. HOWEVER, MUCH REMAINS TO BE LEARNED TO UNDERSTAND THE SPECIFIC ROLE OF THOSE AND OTHER MODIFICATIONS IN THE ASTROGLIAL CONTRIBUTION TO THE VULNERABILITY TO AND MAINTENANCE OF STRESS-RELATED DISORDERS AND DEPRESSION, AND FOR LEVERAGING THAT KNOWLEDGE TO ACHIEVE MORE EFFECTIVE PSYCHIATRIC THERAPIES. 2022 17 2386 33 EPIGENETIC REGULATORY MECHANISMS IN STRESS-INDUCED BEHAVIOR. STRESS RESPONSE IS CONSIDERED TO HAVE ADAPTIVE VALUE FOR ORGANISMS FACED WITH STRESSFUL CONDITION. CHRONIC STRESS HOWEVER ADVERSELY AFFECTS THE PHYSIOLOGY AND MAY LEAD TO NEUROPSYCHIATRIC DISORDERS. REPEATED STRESSFUL EVENTS IN ANIMAL MODELS HAVE BEEN SHOWN TO CAUSE LONG-LASTING CHANGES IN NEURAL CIRCUITRIES AT MOLECULAR, CELLULAR, AND PHYSIOLOGICAL LEVEL, LEADING TO DISORDERS OF MOOD AS WELL AS COGNITION. MOLECULAR STUDIES IN RECENT YEARS HAVE IMPLICATED DIVERSE EPIGENETIC MECHANISMS, INCLUDING HISTONE MODIFICATIONS, DNA METHYLATION, AND NONCODING RNAS, THAT UNDERLIE DYSREGULATION OF GENES IN THE AFFECTED NEURAL CIRCUITRIES IN CHRONIC STRESS-INDUCED PATHOPHYSIOLOGY. A REVIEW OF THE MYRIAD EPIGENETIC REGULATORY MECHANISMS ASSOCIATED WITH NEURAL AND BEHAVIORAL RESPONSES IN ANIMAL MODELS OF STRESS-INDUCED NEUROPSYCHIATRIC DISORDERS IS PRESENTED HERE. THE REVIEW ALSO DEALS WITH CLINICAL EVIDENCE OF THE EPIGENETIC DYSREGULATION OF GENES IN PSYCHIATRIC DISORDERS WHERE CHRONIC STRESS APPEARS TO UNDERLIE THE ETIOPATHOLOGY. 2014 18 632 33 BIOLOGICAL CORRELATES OF EARLY LIFE STRESSFUL EVENTS IN MAJOR DEPRESSIVE DISORDER. MAJOR DEPRESSIVE DISORDER (MDD) IS THE MOST COMMON PSYCHIATRIC DISORDER AND RESPONDS FOR IMPORTANT PSYCHOSOCIAL CONSEQUENCES. STRESSFUL LIFE EVENTS, ESPECIALLY EARLY LIFE STRESS (ELS), CONTRIBUTE TO AN INCREASED PROBABILITY TO DEVELOP MDD, LEADING IN PARTICULAR TO SEVERE AND CHRONIC MANIFESTATION AND UNFAVORABLE TREATMENT OUTCOME. THE ASSOCIATION BETWEEN ELS AND MDD SEEMS TO HAVE BIOLOGICAL BASES, CONSISTING IN DYSREGULATIONS OCCURRING AT DIFFERENT LEVELS. THE AIM OF THIS NARRATIVE REVIEW IS TO PROPOSE AN OVERVIEW OF THE LITERATURE RANGING FROM GENETIC, EPIGENETIC, EXPRESSION AND PROTEIN TO NEUROIMAGING CORRELATES UNDERLYING THIS RELATIONSHIP. A SEARCH ON PUBMED OF STUDIES ASSESSING BIOLOGICAL CORRELATES OF ELS IN MDD DEVELOPMENT, FOCUSING ON HUMAN STUDIES CONDUCTED IN BOTH PERIPHERAL AND BRAIN TISSUES, WAS PERFORMED. EVIDENCE INDICATED THAT THE HYPOTHALAMIC-PITUITARY-ADRENAL (HPA) AXIS AND THE SEROTONERGIC, DOPAMINERGIC, NEUROTROPHIN AND OXYTOCIN SYSTEMS MIGHT PLAY A ROLE IN THE MEDIATION BETWEEN ELS AND MDD. THE MOST CONSISTENT RESULTS WERE FOUND FOR GENETIC AND EPIGENETIC STUDIES AND INDICATED A JOINT INVOLVEMENT OF THE SYSTEMS MENTIONED. EXPRESSION STUDIES ARE LESS NUMEROUS AND POINT TO AN INVOLVEMENT OF STRESS-RELATED SYSTEMS. CONCERNING PROTEIN STUDIES, THE MAIN MEDIATORS ARE MARKERS RELATED TO THE INFLAMMATORY AND IMMUNE SYSTEMS. NEUROIMAGING STUDIES AIMING AT EVALUATING BRAIN ALTERATIONS CONNECTING ELS AND MDD IN RELATION TO BIOMARKERS INDICATED THE HIPPOCAMPUS, THE AMYGDALA AND THE FRONTAL CORTEX AS IMPORTANT ANATOMICAL MEDIATORS. THESE FINDINGS CAN BUILD THE BASES FOR FUTURE RESEARCH AND CLINICAL INTERVENTIONS; INDEED, THE CLARIFICATION OF BIOLOGICAL MECHANISMS MEDIATING THE RELATIONSHIP BETWEEN ELS AND MDD CAN LEAD TO NEW AND INDIVIDUALIZED PREVENTIVE AND THERAPEUTIC POSSIBILITIES. 2021 19 5812 41 STRESS AND ANXIETY: STRUCTURAL PLASTICITY AND EPIGENETIC REGULATION AS A CONSEQUENCE OF STRESS. THE BRAIN IS THE CENTRAL ORGAN OF STRESS AND ADAPTATION TO STRESS BECAUSE IT PERCEIVES AND DETERMINES WHAT IS THREATENING, AS WELL AS THE BEHAVIORAL AND PHYSIOLOGICAL RESPONSES TO THE STRESSOR. THE ADULT, AS WELL AS DEVELOPING BRAIN, POSSESS A REMARKABLE ABILITY TO SHOW REVERSIBLE STRUCTURAL AND FUNCTIONAL PLASTICITY IN RESPONSE TO STRESSFUL AND OTHER EXPERIENCES, INCLUDING NEURONAL REPLACEMENT, DENDRITIC REMODELING, AND SYNAPSE TURNOVER. THIS IS PARTICULARLY EVIDENT IN THE HIPPOCAMPUS, WHERE ALL THREE TYPES OF STRUCTURAL PLASTICITY HAVE BEEN RECOGNIZED AND INVESTIGATED, USING A COMBINATION OF MORPHOLOGICAL, MOLECULAR, PHARMACOLOGICAL, ELECTROPHYSIOLOGICAL AND BEHAVIORAL APPROACHES. THE AMYGDALA AND THE PREFRONTAL CORTEX, BRAIN REGIONS INVOLVED IN ANXIETY AND FEAR, MOOD, COGNITIVE FUNCTION AND BEHAVIORAL CONTROL, ALSO SHOW STRUCTURAL PLASTICITY. ACUTE AND CHRONIC STRESS CAUSE AN IMBALANCE OF NEURAL CIRCUITRY SUBSERVING COGNITION, DECISION MAKING, ANXIETY AND MOOD THAT CAN INCREASE OR DECREASE EXPRESSION OF THOSE BEHAVIORS AND BEHAVIORAL STATES. IN THE SHORT TERM, SUCH AS FOR INCREASED FEARFUL VIGILANCE AND ANXIETY IN A THREATENING ENVIRONMENT, THESE CHANGES MAY BE ADAPTIVE; BUT, IF THE DANGER PASSES AND THE BEHAVIORAL STATE PERSISTS ALONG WITH THE CHANGES IN NEURAL CIRCUITRY, SUCH MALADAPTATION MAY NEED INTERVENTION WITH A COMBINATION OF PHARMACOLOGICAL AND BEHAVIORAL THERAPIES, AS IS THE CASE FOR CHRONIC OR MOOD ANXIETY DISORDERS. WE SHALL REVIEW CELLULAR AND MOLECULAR MECHANISMS, AS WELL AS RECENT WORK ON INDIVIDUAL DIFFERENCES IN ANXIETY-LIKE BEHAVIOR AND ALSO DEVELOPMENTAL INFLUENCES THAT BIAS HOW THE BRAIN RESPONDS TO STRESSORS. FINALLY, WE SUGGEST THAT SUCH AN APPROACH NEEDS TO BE EXTENDED TO OTHER BRAIN AREAS THAT ARE ALSO INVOLVED IN ANXIETY AND MOOD. THIS ARTICLE IS PART OF A SPECIAL ISSUE ENTITLED 'ANXIETY AND DEPRESSION'. 2012 20 5164 34 PRECLINICAL AND CLINICAL EVIDENCE OF DNA METHYLATION CHANGES IN RESPONSE TO TRAUMA AND CHRONIC STRESS. EXPOSURE TO CHRONIC STRESS, EITHER REPEATED SEVERE ACUTE OR MODERATE SUSTAINED STRESS, IS ONE OF THE STRONGEST RISK FACTORS FOR THE DEVELOPMENT OF PSYCHOPATHOLOGIES SUCH AS POST-TRAUMATIC STRESS DISORDER AND DEPRESSION. CHRONIC STRESS IS LINKED WITH SEVERAL LASTING BIOLOGICAL CONSEQUENCES, PARTICULARLY TO THE STRESS ENDOCRINE SYSTEM BUT ALSO AFFECTING INTERMEDIATE PHENOTYPES SUCH AS BRAIN STRUCTURE AND FUNCTION, IMMUNE FUNCTION, AND BEHAVIOR. ALTHOUGH GENETIC PREDISPOSITION CONFERS A PROPORTION OF THE RISK, THE MOST RELEVANT MOLECULAR MECHANISMS DETERMINING THOSE SUSCEPTIBLE AND RESILIENT TO THE EFFECTS OF STRESS AND TRAUMA MAY BE EPIGENETIC. EPIGENETICS REFERS TO THE MECHANISMS THAT REGULATE GENOMIC INFORMATION BY DYNAMICALLY CHANGING THE PATTERNS OF TRANSCRIPTION AND TRANSLATION OF GENES. MOUNTING EVIDENCE FROM PRECLINICAL RODENT AND CLINICAL POPULATION STUDIES STRONGLY SUPPORT THAT EPIGENETIC MODIFICATIONS CAN OCCUR IN RESPONSE TO TRAUMATIC AND CHRONIC STRESS. HERE, WE DISCUSS THIS LITERATURE EXAMINING STRESS-INDUCED EPIGENETIC CHANGES IN PRECLINICAL MODELS AND CLINICAL COHORTS OF STRESS AND TRAUMA OCCURRING EARLY IN LIFE OR IN ADULTHOOD. WE HIGHLIGHT THAT A COMPLEX RELATIONSHIP BETWEEN THE TIMING OF ENVIRONMENTAL STRESSORS AND GENETIC PREDISPOSITIONS LIKELY MEDIATE THE RESPONSE TO CHRONIC STRESS OVER TIME, AND THAT A BETTER UNDERSTANDING OF EPIGENETIC CHANGES IS NEEDED BY FURTHER INVESTIGATIONS IN LONGITUDINAL AND POSTMORTEM BRAIN CLINICAL COHORTS. 2017