Depression is a severe and debilitating mental disorder diagnosed by evaluation of affective, cognitive and physical depression symptoms. Severity of these symptoms strongly impacts individual's ...quality of life and is influenced by a combination of genetic and environmental factors. One of the molecular mechanisms allowing for an interplay between these factors is DNA methylation, an epigenetic modification playing a pivotal role in regulation of brain functioning across lifespan. The aim of this study was to investigate if there are DNA methylation signatures associated with depression symptomatology in order to identify molecular mechanisms contributing to pathophysiology of depression. We performed an epigenome-wide association study (EWAS) of continuous depression symptomatology score measured in a cohort of 724 monozygotic Danish twins (346 males, 378 females). Through EWAS analyses adjusted for sex, age, flow-cytometry based blood cell composition, and twin relatedness structure in the data we identified depression symptomatology score to be associated with blood DNA methylation levels in promoter regions of neuropsin (KLK8, p-value = 4.7 × 10
) and DAZ associated protein 2 (DAZAP2, p-value = 3.13 × 10
) genes. Other top associated probes were located in gene bodies of MAD1L1 (p-value = 5.16 × 10
), SLC29A2 (p-value = 6.15 × 10
) and AKT1 (p-value = 4.47 × 10
), all genes associated before with development of depression. Additionally, the following three measures (a) DNAmAge (calculated with Horvath and Hannum epigenetic clock estimators) adjusted for chronological age, (b) difference between DNAmAge and chronological age, and (c) DNAmAge acceleration were not associated with depression symptomatology score in our cohort. In conclusion, our data suggests that depression symptomatology score is associated with DNA methylation levels of genes implicated in response to stress, depressive-like behaviors, and recurrent depression in patients, but not with global DNA methylation changes across the genome.
Major depressive disorder (MDD) that onsets by adolescence is associated with various deficits in psychosocial functioning. However, adolescent-onset MDD often follows a recurrent course that may ...drive its associated impairment.
To tease apart these two clinical features, we examined the relative associations of age of onset (adolescent versus adult) and course (recurrent versus single episodes) of MDD with a broad range of psychosocial functioning outcomes assessed in early adulthood. Participants comprised a large, population-based sample of male and female twins from the Minnesota Twin Family Study (MTFS; n = 1252) assessed prospectively from ages 17 to 29 years.
A recurrent course of MDD predicted impairment in several psychosocial domains in adulthood, regardless of whether the onset was in adolescence or adulthood. By contrast, adolescent-onset MDD showed less evidence of impairment in adulthood after accounting for recurrence. Individuals with both an adolescent onset and recurrent episodes of MDD represented a particularly severe group with pervasive psychosocial impairment in adulthood.
The negative implications of adolescent-onset MDD for psychosocial functioning in adulthood seem to be due primarily to its frequently recurrent course, rather than its early onset, per se. The results highlight the importance of considering both age of onset and course for understanding MDD and its implications for functioning, and also in guiding targeted intervention efforts.
Gender differences in the prevalence of alcohol use disorder (AUD) have motivated the separate study of its risk factors and consequences in men and women. However, leveraging gender as a third ...variable to help account for the association between risk factors and consequences for AUD could elucidate etiological mechanisms and clinical outcomes.
Using data from a large, community sample followed longitudinally from 17 to 29 years of age, we tested for gender differences in psychosocial risk factors and consequences in adolescence and adulthood after controlling for gender differences in the base rates of AUD and psychosocial factors. Psychosocial factors included alcohol use, other drug use, externalizing and internalizing symptoms, deviant peer affiliation, family adversity, academic problems, attitudes and use of substances by a romantic partner, and adult socio-economic status.
At both ages of 17 and 29 years, mean levels of psychosocial risks and consequences were higher in men and those with AUD. However, the amount of risk exposure in adolescence was more predictive of AUD in women than men. By adulthood, AUD consequences were larger in women than men and internalizing risk had a stronger relationship with AUD in women at both ages.
Despite higher mean levels of risk exposure in men overall, AUD appears to be a more severe disorder in women characterized by higher levels of adolescent risk factors and a greater magnitude of the AUD consequences among women than men. Furthermore, internalizing symptoms appear to be a gender-specific risk factor for AUD in women.
Although common sense suggests that environmental influences increasingly account for individual differences in behavior as experiences accumulate during the course of life, this hypothesis has not ...previously been tested, in part because of the large sample sizes needed for an adequately powered analysis. Here we show for general cognitive ability that, to the contrary, genetic influence increases with age. The heritability of general cognitive ability increases significantly and linearly from 41% in childhood (9 years) to 55% in adolescence (12 years) and to 66% in young adulthood (17 years) in a sample of 11 000 pairs of twins from four countries, a larger sample than all previous studies combined. In addition to its far-reaching implications for neuroscience and molecular genetics, this finding suggests new ways of thinking about the interface between nature and nurture during the school years. Why, despite life's 'slings and arrows of outrageous fortune', do genetically driven differences increasingly account for differences in general cognitive ability? We suggest that the answer lies with genotype-environment correlation: as children grow up, they increasingly select, modify and even create their own experiences in part based on their genetic propensities.
Little is known about the etiology of adolescents' externalizing behavior (Ext) in collectivistic cultures. We aimed to fill this gap by investigating the genetic and environmental influences on Ext ...in Chinese adolescents. The etiological heterogeneity of aggression (AGG) and rule breaking (RB) was also examined.
The study sample included 908 pairs of same-sex twins aged from 10 to 18 years (mean = 13.53 years, s.d. = 2.26). Adolescents' Ext were assessed with the Achenbach System of Empirically Based Assessment including Child Behavior Checklist, Teacher Report Form, and Youth Self-Report.
Univariate genetic analyses showed that genetic influences on all measures were moderate ranging from 34% to 50%, non-shared environmental effects ranged from 23% to 52%, and shared environmental effects were significant in parent- and teacher-reported measures ranging from 29% to 43%. Bivariate genetic analyses indicated that AGG and RB shared large genetic influences (r g = 0.64-0.79) but moderate non-shared environmental factors (r e = 0.34-0.52).
Chinese adolescents' Ext was moderately influenced by genetic factors. AGG and RB had moderate independent genetic and non-shared environmental influences, and thus constitute etiologically distinct dimensions within Ext in Chinese adolescents. The heritability of AGG, in particular, was smaller in Chinese adolescents than suggested by previous data obtained on Western peers. This study suggests that the collectivistic cultural values and Confucianism philosophy may attenuate genetic potential in Ext, especially AGG.
There is a strong etiological link between brain‐derived neurotrophic factor and depression, but the neurocellular mechanisms and gene–environment interactions remain obscure. This study investigated ...whether one functional polymorphism in the brain‐derived neurotrophic factor gene (BDNF Val66Met) modulates the influence of stressful life events on adolescent depressive symptoms. A total of 780 pairs of ethnic Han Chinese adolescent twins, 11–17 years of age, were randomly assigned to one of two subgroups (twin1 and twin2). All subjects were genotyped as Val/Val, Val/Met or Met/Met, and assessed for depressive symptoms using the Children's Depression Inventory. The level of environmental stress was estimated by the frequency of stressful life events using the Life Events Checklist. The frequency of stressful life events was significantly correlated with depressive symptoms (twin1: β = 0.21, P = 0.01; twin2: β = 0.27, P < 0.01), but there was no significant main effect of the BDNF Val66Met genotype on depressive symptoms. In both subgroups, however, the interaction between the BDNF Val66Met genotype and stressful life event frequency was significant (twin1: β = 0.19, P = 0.01; twin2: β = 0.15, P = 0.04); individuals with one or two Val alleles demonstrated a greater susceptibility to both the detrimental effects of higher stress and the beneficial effects of lower stress compared to the Met/Met genotype. These findings support the ‘differential‐susceptibility’ hypothesis, whereby the BDNF Val allele modulates the influence of environmental stress on depression by enhancing the neuroplastic response to all life events.
The BDNF Val66Met polymorphism interacts with recent stressful life events and has impact on adolescent depressive symptoms.
Abstract The epigenetic clock, also known as DNA methylation age (DNAmAge), represents age-related changes of DNA methylation at multiple sites of the genome and is suggested to be a biomarker for ...biological age. Elevated blood DNAmAge is associated with all-cause mortality, with the strongest effects reported in a recent intrapair twin study where epigenetically older twins had increased mortality risk in comparison to their co-twins. In the study presented here, we hypothesize that DNAmAge in blood is associated with cross-sectional and longitudinal cognitive abilities in middle-aged individuals. In 486 monozygotic twins, we investigated the association of DNAmAge, difference between DNAmAge and chronological age and age acceleration with cognition. Despite using a powerful paired twin design, we found no evidence for association of blood DNAmAge with cognitive abilities. This observation was confirmed in unpaired analyses, where DNAmAge initially correlated with cognitive abilities, until adjusting for chronological age. Overall, our study shows that for middle-aged individuals DNAmAge calculated in blood does not correlate with cognitive abilities.
It is well documented that memory is heritable and that older adults tend to have poorer memory performance than younger adults. However, whether the magnitudes of genetic and environmental ...contributions to late-life verbal episodic memory ability differ from those at earlier ages remains unresolved. Twins from 12 studies participating in the Interplay of Genes and Environment in Multiple Studies (IGEMS) consortium constituted the analytic sample. Verbal episodic memory was assessed with immediate word list recall (N = 35,204 individuals; 21,792 twin pairs) and prose recall (N = 3805 individuals; 2028 twin pairs), with scores harmonized across studies. Average test performance was lower in successively older age groups for both measures. Twin models found significant age moderation for both measures, with total inter-individual variance increasing significantly with age, although it was not possible definitively to attribute the increase specifically to either genetic or environmental sources. Pooled results across all 12 studies were compared to results where we successively dropped each study (leave-one-out) to assure results were not due to an outlier. We conclude the models indicated an overall increase in variance for verbal episodic memory that was driven by a combination of increases in the genetic and nonshared environmental parameters that were not independently statistically significant. In contrast to reported results for other cognitive domains, differences in environmental exposures are comparatively important for verbal episodic memory, especially word list learning.
•Verbal episodic memory performance is poorer at older ages compared to midlife.•Individual variance in verbal episodic memory shows an increase across age.•Environmental variance unique to individuals is more important than genetic variance.•Genetic variance is greater for remembering a prose passage than a list of words.
Previous studies have shown that genetic risk for externalizing (EXT) disorders is greater in the context of adverse family environments during adolescence, but it is unclear whether these effects ...are long lasting. The current study evaluated developmental changes in gene-environment interplay in the concurrent and prospective associations between parent-child relationship problems and EXT at ages 18 and 25 years.
The sample included 1382 twin pairs (48% male) from the Minnesota Twin Family Study, participating in assessments at ages 18 years (mean = 17.8, s.d. = 0.69 years) and 25 years (mean = 25.0, s.d. = 0.90 years). Perceptions of parent-child relationship problems were assessed using questionnaires. Structured interviews were used to assess symptoms of adult antisocial behavior and nicotine, alcohol and illicit drug dependence.
We detected a gene-environment interaction at age 18 years, such that the genetic influence on EXT was greater in the context of more parent-child relationship problems. This moderation effect was not present at age 25 years, nor did parent-relationship problems at age 18 years moderate genetic influence on EXT at age 25 years. Rather, common genetic influences accounted for this longitudinal association.
Gene-environment interaction evident in the relationship between adolescent parent-child relationship problems and EXT is both proximal and developmentally limited. Common genetic influence, rather than a gene-environment interaction, accounts for the long-term association between parent-child relationship problems at age 18 years and EXT at age 25 years. These results are consistent with a relatively pervasive importance of gene-environmental correlation in the transition from late adolescence to young adulthood.
Previous research indicates that alcohol and drug dependence constitute aspects of a general vulnerability to externalizing disorders that accounts for much of the parent-offspring resemblance for ...these and related disorders. This study examined how adolescent offspring risk for externalizing psychopathology varies with respect to parental alcoholism and illicit drug dependence.
Data from the Minnesota Twin Family Study, a community-based investigation of adolescents (age 17 years, n=1252) and their parents, were used. Lifetime diagnoses of alcohol and drug dependence (among both parents and offspring) and offspring attention deficit hyperactivity disorder, oppositional defiant disorder, conduct disorder, adult antisocial behavior, and nicotine dependence were assessed via structured interviews.
Parental alcohol dependence and parental drug dependence were similarly associated with increased risk for nearly all offspring disorders, with offspring of alcohol and drug-dependent parents having approximately 2-3 times the odds for developing a disorder by late adolescence compared to low-risk offspring. Compared to parental dependence on other illicit drugs, parental cannabis dependence was associated with weaker increased risk for offspring externalizing disorders.
Both parental alcohol and drug dependence are independently associated with an increased risk for a broad range of externalizing psychopathology among late-adolescent offspring.
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