Human and animal research into sex-specific effects of child abuse

[Gender characteristics of depressive disorders: clinical, psychological, neurobiological and translational aspects]

Various studies have indicated that the prevalence of depression is almost twice as high among women as among men. A major factor associated with the development of depression and other affective disorders are adverse and psychologically traumatic life events that contribute to changes in the neuroendocrine system, altering the capacity to adapt to stress. These changes are involved in the pathogenesis of mental disorders, along with genetic and other factors, and are to a significant degree regulated by gender dependent mechanisms. While women have a high prevalence of depressive disorders, men show a higher rate of alcohol and substance abuse. These differences in the epidemiology are most likely explained by different predisposition to mental disorders in men and women and a diversity of biological consequences to adverse life events. Taking this into account, there is a need for a critical review of currently used approaches to modeling depressive disorders in preclinical studies, including the use of animals of both sexes. Adaptation of experimental models and protocols taking into account gender characteristics of neuroendocrine changes in response to stress, as well as structural-morphological, electrophysiological, molecular, genetic and epigenetic features, will significantly increase the translational validity of experimental work.

Early life stress is associated with reduced avoidance of threatening facial expressions

Early neglect or maltreatment has been associated with changes in children's processing of emotional facial expressions, including a hypersensitivity to the emotion of anger. This may facilitate the avoidance of danger in a maltreating environment. However, few studies have examined whether experiences of early life stress (ELS) are associated with atypical avoidance responses towards emotional facial expressions, or whether the effects of ELS can be observed in adult participants. The present study therefore examined the effects of ELS on adults' approach-avoidance tendencies towards angry, happy, and neutral facial expressions. Surprisingly, higher levels of ELS were associated with reduced avoidance of angry facial expressions among individuals with no evidence of mental illness. In contrast, there was no evidence of a relationship between ELS and avoidance of angry facial expressions among individuals with experience of mental illness. These novel findings suggest that ELS-related changes in social cognition can be observed years after the ELS itself occurred.

Sex differences in neurodevelopmental and common mental disorders examined from three epidemiological perspectives

Sex differences in neurodevelopmental and common mental disorders are a ubiquitous, well-known, though poorly understood phenomenon. This study examined the issue from three epidemiological perspectives: congruence in age of onset, distribution of sex-ratios with respect to age of onset and similarity of comorbidity and risk factor patterns. The analysis was based on data from the population-based PsyCoLaus study (N = 4874, age 35-82 y). Congruence in age of onset and distribution of sex-ratios were examined with the Mann-Whitney test and cluster analysis. The similarity of comorbidity and risk factor patterns, which were represented by 35 variables, was assessed with the Jaccard coefficient and, after factor analysis, with Tucker's congruence coefficient. While age of onset parameters differed little by sex, the sex ratio varied markedly both in early and in late onset disorders. Moreover, the Jaccard coefficients for most disorders indicated that the similarity of comorbidity and further association patterns was low. Similarly, Tucker's congruence coefficient remained below the range of fair similarity in all factor combinations. In sum, sex differences in common mental disorders were impressively reflected by diverging sex ratios and comorbidity / risk factor patterns. This outcome supports the notion that most mental disorders need a sex-specific etiopathogenetic understanding.

Altered fear processing in adolescents with a history of severe childhood maltreatment: an fMRI study

BACKGROUND

Children with a history of maltreatment suffer from altered emotion processing but the neural basis of this phenomenon is unknown. This pioneering functional magnetic resonance imaging (fMRI) study investigated the effects of severe childhood maltreatment on emotion processing while controlling for psychiatric conditions, medication and substance abuse.

METHOD

Twenty medication-naive, substance abuse-free adolescents with a history of childhood abuse, 20 psychiatric control adolescents matched on psychiatric diagnoses but with no maltreatment and 27 healthy controls underwent a fMRI emotion discrimination task comprising fearful, angry, sad happy and neutral dynamic facial expressions.

RESULTS

Maltreated participants responded faster to fearful expressions and demonstrated hyper-activation compared to healthy controls of classical fear-processing regions of ventromedial prefrontal cortex (vmPFC) and anterior cingulate cortex, which survived at a more lenient threshold relative to psychiatric controls. Functional connectivity analysis, furthermore, demonstrated reduced connectivity between left vmPFC and insula for fear in maltreated participants compared to both healthy and psychiatric controls.

CONCLUSIONS

The findings show that people who have experienced childhood maltreatment have enhanced fear perception, both at the behavioural and neurofunctional levels, associated with enhanced fear-related ventromedial fronto-cingulate activation and altered functional connectivity with associated limbic regions. Furthermore, the connectivity adaptations were specific to the maltreatment rather than to the developing psychiatric conditions, whilst the functional changes were only evident at trend level when compared to psychiatric controls, suggesting a continuum. The neurofunctional hypersensitivity of fear-processing networks may be due to childhood over-exposure to fear in people who have been abused.

Altered Functional Connectivity of Fronto-Cingulo-Striatal Circuits during Error Monitoring in Adolescents with a History of Childhood Abuse

Childhood maltreatment is associated with error hypersensitivity. We examined the effect of childhood abuse and abuse-by-gene (5-HTTLPR, MAOA) interaction on functional brain connectivity during error processing in medication/drug-free adolescents. Functional connectivity was compared, using generalized psychophysiological interaction (gPPI) analysis of functional magnetic resonance imaging (fMRI) data, between 22 age- and gender-matched medication-naïve and substance abuse-free adolescents exposed to severe childhood abuse and 27 healthy controls, while they performed an individually adjusted tracking stop-signal task, designed to elicit 50% inhibition failures. During inhibition failures, abused participants relative to healthy controls exhibited reduced connectivity between right and left putamen, bilateral caudate and anterior cingulate cortex (ACC), and between right supplementary motor area (SMA) and right inferior and dorsolateral prefrontal cortex. Abuse-related connectivity abnormalities were associated with longer abuse duration. No group differences in connectivity were observed for successful inhibition. The findings suggest that childhood abuse is associated with decreased functional connectivity in fronto-cingulo-striatal networks during error processing. Furthermore that the severity of connectivity abnormalities increases with abuse duration. Reduced connectivity of error detection networks in maltreated individuals may be linked to constant monitoring of errors in order to avoid mistakes which, in abusive contexts, are often associated with harsh punishment.

Reduced functional connectivity of fronto-parietal sustained attention networks in severe childhood abuse

Childhood maltreatment is associated with attention deficits. We examined the effect of childhood abuse and abuse-by-gene (5-HTTLPR, MAOA, FKBP5) interaction on functional brain connectivity during sustained attention in medication/drug-free adolescents. Functional connectivity was compared, using generalised psychophysiological interaction (gPPI) analysis of functional magnetic resonance imaging (fMRI) data, between 21 age-and gender-matched adolescents exposed to severe childhood abuse and 27 healthy controls, while they performed a parametrically modulated vigilance task requiring target detection with a progressively increasing load of sustained attention. Behaviourally, participants exposed to childhood abuse had increased omission errors compared to healthy controls. During the most challenging attention condition abused participants relative to controls exhibited reduced connectivity, with a left-hemispheric bias, in typical fronto-parietal attention networks, including dorsolateral, rostromedial and inferior prefrontal and inferior parietal regions. Abuse-related connectivity abnormalities were exacerbated in individuals homozygous for the risky C-allele of the single nucleotide polymorphism rs3800373 of the FK506 Binding Protein 5 (FKBP5) gene. Findings suggest that childhood abuse is associated with decreased functional connectivity in fronto-parietal attention networks and that the FKBP5 genotype moderates neurobiological vulnerability to abuse. These findings represent a first step towards the delineation of abuse-related neurofunctional connectivity abnormalities, which hopefully will facilitate the development of specific treatment strategies for victims of childhood maltreatment.

Associations between the FKBP5 haplotype, exposure to violence and anxiety in females

The gene that encodes the FK506-binding protein 5 (FKBP5) is regarded as a candidate for investigating how negative life events interact with a genetic predisposition to stress-related disorders, such as depression and anxiety. Given the role of FKBP5 as an important regulator of stress responses, we aimed to investigate if single-nucleotide polymorphisms (SNPs) in FKBP5-in the presence/absence of exposure to violence-are associated with symptoms of depression and anxiety. Data from two community-based samples of adolescents (n=1705) and young adults (n=1800) regarding ratings on depression, anxiety, exposure to violence and FKBP5 genotype were collected. A risk haplogenotype including the minor alleles of seven common SNPs in the FKBP5 (rs3800373, rs9296158, rs7748266, rs1360780, rs9394309, rs9470080 and rs4713916) conferred higher ratings on anxiety among females, but not males, in the presence of violence. Exposure to violence and female sex were associated with higher ratings on both depression and anxiety, with the exception of ratings on depression among young adults, on which sex had no effect. Ratings on depression were not associated with the haplogenotype. These findings may correspond to differences in the regulation of the HPA axis and with the higher vulnerability to anxiety in females.

A putatively functional polymorphism in the HTR2C gene is associated with depressive symptoms in white females reporting significant life stress

Psychosocial stress is well known to be positively associated with subsequent depressive symptoms. Cortisol response to stress may be one of a number of biological mechanisms that links psychological stress to depressive symptoms, although the precise causal pathway remains unclear. Activity of the x-linked serotonin 5-HTR2C receptor has also been shown to be associated with depression and with clinical response to antidepressant medications. We recently demonstrated that variation in a single nucleotide polymorphism on the HTR2C gene, rs6318 (Ser23Cys), is associated with different cortisol release and short-term changes in affect in response to a series of stress tasks in the laboratory. Based on this observation, we decided to examine whether rs6318 might moderate the association between psychosocial stress and subsequent depressive symptoms. In the present study we use cross-sectional data from a large population-based sample of young adult White men (N = 2,366) and White women (N = 2,712) in the United States to test this moderation hypothesis. Specifically, we hypothesized that the association between self-reported stressful life events and depressive symptoms would be stronger among homozygous Ser23 C females and hemizygous Ser23 C males than among Cys23 G carriers. In separate within-sex analyses a genotype-by-life stress interaction was observed for women (p = .022) but not for men (p = .471). Homozygous Ser23 C women who reported high levels of life stress had depressive symptom scores that were about 0.3 standard deviations higher than female Cys23 G carriers with similarly high stress levels. In contrast, no appreciable difference in depressive symptoms was observed between genotypes at lower levels of stress. Our findings support prior work that suggests a functional SNP on the HTR2C gene may confer an increased risk for depressive symptoms in White women with a history of significant life stress.

Environmental Health Factors and Sexually Dimorphic Differences in Behavioral Disruptions

Mounting evidence suggests that environmental factors-in particular, those that we are exposed to during perinatal life-can dramatically shape the organism's risk for later diseases, including neurobehavioral disorders. However, depending on the environmental insult, one sex may demonstrate greater vulnerability than the other sex. Herein, we focus on two well-defined extrinsic environmental factors that lead to sexually dimorphic behavioral differences in animal models and linkage in human epidemiological studies. These include maternal or psychosocial stress (such as social stress) and exposure to endocrine-disrupting compounds (such as one of the most prevalent, bisphenol A [BPA]). In general, the evidence suggests that early environmental exposures, such as BPA and stress, lead to more pronounced behavioral deficits in males than in females, whereas female neurobehavioral patterns are more vulnerable to later in life stress. These findings highlight the importance of considering sex differences and developmental timing when examining the effects of environmental factors on later neurobehavioral outcomes.

Behavioral and neuroendocrine consequences of juvenile stress combined with adult immobilization in male rats

Exposure to stress during childhood and adolescence increases vulnerability to developing several psychopathologies in adulthood and alters the activity of the hypothalamic-pituitary-adrenal (HPA) axis, the prototypical stress system. Rodent models of juvenile stress appear to support this hypothesis because juvenile stress can result in reduced activity/exploration and enhanced anxiety, although results are not always consistent. Moreover, an in-depth characterization of changes in the HPA axis is lacking. In the present study, the long-lasting effects of juvenile stress on adult behavior and HPA function were evaluated in male rats. The juvenile stress consisted of a combination of stressors (cat odor, forced swim and footshock) during postnatal days 23-28. Juvenile stress reduced the maximum amplitude of the adrenocorticotropic hormone (ACTH) levels (reduced peak at lights off), without affecting the circadian corticosterone rhythm, but other aspects of the HPA function (negative glucocorticoid feedback, responsiveness to further stressors and brain gene expression of corticotrophin-releasing hormone and corticosteroid receptors) remained unaltered. The behavioral effects of juvenile stress itself at adulthood were modest (decreased activity in the circular corridor) with no evidence of enhanced anxiety. Imposition of an acute severe stressor (immobilization on boards, IMO) did not increase anxiety in control animals, as evaluated one week later in the elevated-plus maze (EPM), but it potentiated the acoustic startle response (ASR). However, acute IMO did enhance anxiety in the EPM, in juvenile stressed rats, thereby suggesting that juvenile stress sensitizes rats to the effects of additional stressors.