Genetic and environmental determinants of stressful life events and their overlap with depression and neuroticism

Patterns of stressful life events and polygenic scores for five mental disorders and neuroticism among adults with depression

The dominant ('general') version of the diathesis-stress theory of depression views stressors and genetic vulnerability as independent risks. In the Australian Genetics of Depression Study (N = 14,146; 75% female), we tested whether polygenic scores (PGS) for major depression, bipolar disorder, schizophrenia, anxiety, ADHD, and neuroticism were associated with reported exposure to 32 childhood, past-year, lifetime, and accumulated stressful life events (SLEs). In false discovery rate-corrected models, the clearest PGS-SLE relationships were for the ADHD- and depression-PGSs, and to a lesser extent, the anxiety- and schizophrenia-PGSs. We describe the associations for childhood and accumulated SLEs, and the 2-3 strongest past-year/lifetime SLE associations. Higher ADHD-PGS was associated with all childhood SLEs (emotional abuse, emotional neglect, physical neglect; ORs = 1.09-1.14; p's < 1.3 × 10-5), more accumulated SLEs, and reported exposure to sudden violent death (OR = 1.23; p = 3.6 × 10-5), legal troubles (OR = 1.15; p = 0.003), and sudden accidental death (OR = 1.14; p = 0.006). Higher depression-PGS was associated with all childhood SLEs (ORs = 1.07-1.12; p's < 0.013), more accumulated SLEs, and severe human suffering (OR = 1.17; p = 0.003), assault with a weapon (OR = 1.12; p = 0.003), and living in unpleasant surroundings (OR = 1.11; p = 0.001). Higher anxiety-PGS was associated with childhood emotional abuse (OR = 1.08; p = 1.6 × 10-4), more accumulated SLEs, and serious accident (OR = 1.23; p = 0.004), physical assault (OR = 1.08; p = 2.2 × 10-4), and transportation accident (OR = 1.07; p = 0.001). Higher schizophrenia-PGS was associated with all childhood SLEs (ORs = 1.12-1.19; p's < 9.3-8), more accumulated SLEs, and severe human suffering (OR = 1.16; p = 0.003). Higher neuroticism-PGS was associated with living in unpleasant surroundings (OR = 1.09; p = 0.007) and major financial troubles (OR = 1.06; p = 0.014). A reversed pattern was seen for the bipolar-PGS, with lower odds of reported physical assault (OR = 0.95; p = 0.014), major financial troubles (OR = 0.93; p = 0.004), and living in unpleasant surroundings (OR = 0.92; p = 0.007). Genetic risk for several mental disorders influences reported exposure to SLEs among adults with moderately severe, recurrent depression. Our findings emphasise that stressors and diatheses are inter-dependent and challenge diagnosis and subtyping (e.g., reactive/endogenous) based on life events.

Chronic exposure to aflatoxin B1 increases hippocampal microglial pyroptosis and vulnerability to stress in mice

BACKGROUND

Chronic aflatoxin B1 (AFB1) exposure may increase the risk of multiple neuropsychiatric disorders. Stress is considered one of the main contributors to major depressive disorder. Whether and how chronic AFB1 exposure affects vulnerability to stress is unclear.

METHODS

Mice were exposed for three weeks to AFB1 (100 µg/kg/d) and/or chronic mild stress (CMS). The vulnerability behaviors in response to stress were assessed in the forced swimming test (FST), sucrose preference test (SPT), and tail suspension test (TST). Microglial pyroptosis was investigated using immunofluorescence, enzyme-linked immunosorbent assays, and western blot assay in the hippocampus of mice. Hippocampal neurogenesis and the effects of AFB1-treated microglia on proliferation and differentiation of neural stem/precursor cells (NSPCs) were assessed via immunofluorescence in the hippocampus of mice.

RESULTS

Mice exposed to CMS in the presence of AFB1 exhibited markedly greater vulnerability to stress than mice treated with CMS or AFB1 alone, as indicated by reduced sucrose preference and longer immobility time in the forced swimming test. Chronic aflatoxin B1 exposure resulted in changes in the microglial morphology and increase in TUNEL⁺ microglia and GSDMD⁺ microglia in the hippocampal dentate gyrus. When mice were exposed to both CMS and AFB1, pyroptosis-related molecules (such as NLRP3, caspase-1, GSDMD-N, and interleukin-1β) were significantly upregulated in the hippocampus. These molecules were also significantly enhanced by AFB1 in primary microglial cultures. AFB1-treated mice showed decrease in the numbers of BrdU⁺, BrdU-DCX⁺, and BrdU-NeuN⁺ cells in the hippocampal dentate gyrus, as well as the percentages of BrdU⁺ cells that were NeuN⁺ in the presence or absence of CMS when compared with vehicle-treated mice. The combination of AFB1 and CMS exacerbated these effects to an even greater extent. The number of DCX⁺ cells correlated negatively with the percentage of ameboid microglia, TUNEL⁺ microglia and GSDMD⁺ microglia in the hippocampal dentate gyrus. AFB1-treated microglia suppressed the proliferation and neuronal differentiation of NSPCs in vitro.

CONCLUSION

Chronic AFB1 exposure induces microglial pyroptosis, promoting an adverse neurogenic microenvironment that impairs hippocampal neurogenesis, which may render mice more vulnerable to stress.

Current Knowledge of the Antidepressant Activity of Chemical Compounds from Crocus sativus L

Psychotropic effect of Crocus sativus L. (family Iridaceae) biologically active chemical compounds are quite well documented and they can therefore be used in addition to the conventional pharmacological treatment of depression. This systematic review on antidepressant compounds in saffron crocus and their mechanisms of action and side effects is based on publications released between 1995−2022 and data indexed in 15 databases under the following search terms: antidepressant effect, central nervous system, Crocus sativus, cognitive impairement, crocin, crocetin, depression, dopamine, dopaminergic and serotonergic systems, picrocrocin, phytotherapy, neurotransmitters, safranal, saffron, serotonin, and biologically active compounds. The comparative analysis of the publications was based on 414 original research papers. The investigated literature indicates the effectiveness and safety of aqueous and alcoholic extracts and biologically active chemical compounds (alkaloids, anthocyanins, carotenoids, flavonoid, phenolic, saponins, and terpenoids) isolated from various organs (corms, leaves, flower petal, and stigmas) in adjuvant treatment of depression and anxiety. Monoamine reuptake inhibition, N-methyl-d-aspartate (NMDA) receptor antagonism, and gamma-aminobutyric acid (GABA)-α agonism are the main proposed mechanism of the antidepressant action. The antidepressant and neuroprotective effect of extract components is associated with their anti-inflammatory and antioxidant activity. The mechanism of their action, interactions with conventional drugs and other herbal preparations and the safety of use are not fully understood; therefore, further detailed research in this field is necessary. The presented results regarding the application of C. sativus in phytotherapy are promising in terms of the use of herbal preparations to support the treatment of depression. This is particularly important given the steady increase in the incidence of this disease worldwide and social effects.

The P-factor and its genomic and neural equivalents: an integrated perspective

Different psychiatric disorders and symptoms are highly correlated in the general population. A general psychopathology factor (or "P-factor") has been proposed to efficiently describe this covariance of psychopathology. Recently, genetic and neuroimaging studies also derived general dimensions that reflect densely correlated genomic and neural effects on behaviour and psychopathology. While these three types of general dimensions show striking parallels, it is unknown how they are conceptually related. Here, we provide an overview of these three general dimensions, and suggest a unified interpretation of their nature and underlying mechanisms. We propose that the general dimensions reflect, in part, a combination of heritable 'environmental' factors, driven by a dense web of gene-environment correlations. This perspective calls for an update of the traditional endophenotype framework, and encourages methodological innovations to improve models of gene-brain-environment relationships in all their complexity. We propose concrete approaches, which by taking advantage of the richness of current large databases will help to better disentangle the complex nature of causal factors underlying psychopathology.

Depresión Infanto-Juvenil y exposición temprana a la violencia

Este artículo de revisión bibliográfica  tiene como objetivo conocer las aproximaciones teóricas de la depresión en el curso de vida infanto juvenil, a partir de la exposición temprana a situaciones de violencia, en tanto los procesos de mielinización se obstruyen, en la medida en que en los primeros años de vida, se es  víctima de violencia, influyendo esto directamente en alteraciones, cognitivas, comportamentales y emocionales. Resulta del interés en conocer los avances de  las disciplinas, las metodologías, las categorías y las preguntas que están motivando a los investigadores sobre el la depresión como síntoma arraigado en la violencia, hoy.  El análisis de la información fue desarrollada a través del estado del arte que constaba de 8 (ocho) ítems y 50 (cincuenta) filas, con el fin de ordenar y categorizar la información a partir de  conceptos relacionales. Las perspectivas disciplinares indagadas en esta revisión son la Psicología, la psiquiatría, la neuropsicología y las ciencias sociales. Las principales categorías indagadas por los autores son: mielinización, violencia infantil, depresión, consecuencias Neuropsicológicas y emocionales de la violencia. Las preguntas que formulan los investigadores se  ubican en cuatro campos: procesos neurobiológicos, violencia y maltrato infantil, pautas de crianza, depresión infanto juvenil, y  trastornos comportamentales, emocionales y cognitivos. Por los resultados obtenidos, se identificó que los problemas cardinales abordados en las investigaciones son, la violencia intrafamiliar, las pautas de crianza como uno de los ejes articuladores, y la depresión infanto juvenil.

Reciprocal effects of neuroticism and life stress in adolescence

BACKGROUND

Stressful life experiences and personality can influence one another. Personality may contribute to the amount and type of stress individuals experience, which is referred to as a selection effect. Life stress may also impact one's personality, which is referred to as a socialization effect. It was hypothesized that neuroticism would predict increased chronic and episodic stress (selection effect) and that chronic and episodic stress would predict increased neuroticism (socialization effect).

METHODS

The current study investigated selection and socialization effects of neuroticism and life stress over a three-year period in 627 adolescents. Life stress data were examined in terms of duration (chronic versus episodic) and type (interpersonal versus non-interpersonal). Episodic stress data were examined as dependent or independent.

RESULTS

The results from ten cross-lagged panel models provided some evidence for significant selection and socialization effects depending on stress type. Over three years, we observed that neuroticism increases interpersonal chronic stress and non-interpersonal stressful events (selection effects) and that dependent non-interpersonal stressful events and chronic stress increase neuroticism (socialization effects).

LIMITATIONS

Study limitations include a lack of a lifespan perspective and a statistical approach that does not differentiate between- from within-person variance.

CONCLUSIONS

Findings suggest the value of attending to stress response as well as targeting neuroticism in prevention and intervention approaches in adolescents.

Childhood maltreatment and DNA methylation: A systematic review

DNA methylation (DNAm) - an epigenetic process that regulates gene expression - may represent a mechanism for the biological embedding of early traumatic experiences, including childhood maltreatment. Here, we conducted the first systematic review of human studies linking childhood maltreatment to DNAm. In total, 72 studies were included in the review (2008-2018). The majority of extant studies (i) were based on retrospective data in adults, (ii) employed a candidate gene approach (iii) focused on global maltreatment, (iv) were based on easily accessible peripheral tissues, typically blood; and (v) were cross-sectional. Two-thirds of studies (n = 48) also examined maltreatment-related outcomes, such as stress reactivity and psychiatric symptoms. While findings generally support an association between childhood maltreatment and altered patterns of DNAm, factors such as the lack of longitudinal data, low comparability across studies as well as potential genetic and 'pre-exposure' environmental confounding currently limit the conclusions that can be drawn. Key challenges are discussed and concrete recommendations for future research are provided to move the field forward.

Prenatal and childhood adverse life events, inflammation and depressive symptoms across adolescence

BACKGROUND

No study has investigated the role of inflammation in explaining the association between early exposures to adverse life events and depressive symptoms in adolescence.

METHOD

Using data from the Avon Longitudinal Study of Parents and Children, we tested if inflammatory markers [serum C-reactive protein (CRP) and interleukin 6 (IL-6)] at age 9 years mediate the association between adverse life events, measured separately for the prenatal (since the beginning of pregnancy) and the childhood (ages 0-9 years) periods, and the development of depressive symptoms at ages 10-17 years. Data (n = 4,263) were analyzed using mediation analysis in a latent growth curve modeling framework.

RESULTS

Depressive symptoms at the beginning of adolescence (age 10) were associated with the number of prenatal events, the number of events around birth and the increase in events over time in childhood (ages 0-9), even after adjustment for confounders. IL-6 partially mediated the association between increasing exposure to events over time in childhood and depressive symptoms at the beginning of adolescence. IL-6 did not mediate any other association between events and symptoms. There was no evidence for mediation by CRP, which was generally unrelated to exposure to events.

LIMITATIONS

The small size of the mediation effect and the robust direct effects of events prenatally and around birth suggest there are multiple routes from early stressors to adolescent depression.

CONCLUSIONS

In the general adolescent population, increasing exposure to psychosocial stressors over time during childhood is associated with the early onset of depressive symptoms, partly via increasing levels of plasma IL-6.

Genetic influences on treatment-seeking for common mental health problems in the UK biobank

The majority of those who experience clinical anxiety and/or depressive symptoms in the population do not receive treatment. Studies investigating inequalities in treatment outcomes rarely consider that individuals respond differently to their experience of the environment. Much of our environment is under genetic influence, via our behaviour, whereby individuals actively select their experiences. If genes influence who seeks and receives treatment, selection bias will confound genomic studies of treatment response. Furthermore, if some individuals are at high genetic risk of needing but not commencing treatment, then greater efforts could be made to engage them. The role of common genetic variation on four lifetime treatment-seeking behaviours (treatment-seeking, treatment-receipt, self-help, self-medication with alcohol/drugs) was examined in participants of the UK Biobank (sample size range: 48,106 - 75,322). Treatment-related behaviours were only modestly heritable in these data. Nonetheless, genetic correlations reveal substantial genetic overlap between lifetime treatment-related behaviours and psychiatric disorders, symptoms and behavioural traits. To our knowledge, this is the first study to examine genetic influences on treatment-related behaviours. Further work is required to determine whether genetic factors could be used alongside clinical, social and demographic factors to identify at risk groups and inform strategies which target early intervention.

Dispositional negativity, cognition, and anxiety disorders: An integrative translational neuroscience framework

When extreme, anxiety can become debilitating. Anxiety disorders, which often first emerge early in development, are common and challenging to treat, yet the underlying mechanisms have only recently begun to come into focus. Here, we review new insights into the nature and biological bases of dispositional negativity, a fundamental dimension of childhood temperament and adult personality and a prominent risk factor for the development of pediatric and adult anxiety disorders. Converging lines of epidemiological, neurobiological, and mechanistic evidence suggest that dispositional negativity increases the likelihood of psychopathology via specific neurocognitive mechanisms, including attentional biases to threat and deficits in executive control. Collectively, these observations provide an integrative translational framework for understanding the development and maintenance of anxiety disorders in adults and youth and set the stage for developing improved intervention strategies.