A Population Based Twin Study of Sex Differences in Depressive Symptoms

The genetic background of the associations between sense of coherence and mental health, self-esteem and personality

PURPOSE

Sense of coherence (SOC) represents coping and can be considered an essential component of mental health. SOC correlates with mental health and personality, but the background of these associations is poorly understood. We analyzed the role of genetic factors behind the associations of SOC with mental health, self-esteem and personality using genetic twin modeling and polygenic scores (PGS).

METHODS

Information on SOC (13-item Orientation of Life Questionnaire), four mental health indicators, self-esteem and personality (NEO Five Factor Inventory Questionnaire) was collected from 1295 Finnish twins at 20-27 years of age.

RESULTS

In men and women, SOC correlated negatively with depression, alexithymia, schizotypal personality and overall mental health problems and positively with self-esteem. For personality factors, neuroticism was associated with weaker SOC and extraversion, agreeableness and conscientiousness with stronger SOC. All these psychological traits were influenced by genetic factors with heritability estimates ranging from 19 to 66%. Genetic and environmental factors explained these associations, but the genetic correlations were generally stronger. The PGS of major depressive disorder was associated with weaker, and the PGS of general risk tolerance with stronger SOC in men, whereas in women the PGS of subjective well-being was associated with stronger SOC and the PGSs of depression and neuroticism with weaker SOC.

CONCLUSION

Our results indicate that a substantial proportion of genetic variation in SOC is shared with mental health, self-esteem and personality indicators. This suggests that the correlations between these traits reflect a common neurobiological background rather than merely the influence of external stressors.

Research Review: Developmental origins of depression - a systematic review and meta-analysis

BACKGROUND

Many observational studies have found a direct association between adverse in utero, perinatal and postnatal exposures and offspring's depression. These findings are consistent with the 'developmental origins of disease hypothesis'. But no review has comprehensively summarized the roles of these exposures. This review aims to systematically scrutinize the strength of associations between individual prenatal, perinatal, and postnatal exposures and subsequent depression in offspring.

METHODS

We conducted a systematic review and meta-analysis to synthesize the literature from the EMBASE, HealthStar, PsychoInfo, and Medline databases since their inception to September 1, 2019. English language articles on population-based prospective cohort studies examining the associations between in utero, perinatal, and postnatal exposures and offspring's depression were searched. Random-effects models were used to calculate pooled estimates, and heterogeneity and sensitivity tests were conducted to explore potential confounders in the relationships of depression and early-life factors. Qualitative analysis was also conducted.

RESULTS

Sixty-four prospective cohort studies with 28 exposures studied in the relationships to offspring's depression met inclusion criteria. The meta-analysis found 12 prenatal, perinatal, and postnatal characteristics were associated with an increased risk of depression in offspring: low birth weight, premature birth, small gestational age, maternal education, socioeconomic status, having younger parents (<20 years), having older parents (≥35 years), maternal smoking, paternal smoking, maternal stress, maternal anxiety, and prenatal depression. Heterogeneity and sensitivity tests supported the findings. By and large, study characteristics had no effects on conclusions. Qualitative analyses generally supported the findings of meta-analysis and reported on additional risk factors.

CONCLUSIONS

This review provides a robust and comprehensive overview of the lasting psychopathological effects of in utero, perinatal, and postnatal exposures. The findings highlight the need for clinical and public health interventions focusing on the identified risk factors. Large prospective cohort studies are warranted to investigate the combined effects of multiple co-existing early-life exposures.

Etiological pathways of depressive and anxiety symptoms linked to personality traits: A genetically-informative longitudinal study

BACKGROUND

The comorbidity of depression and anxiety is associated with an increased risk of prolonged adverse mental health status. However, little is currently known about their genetic and environmental influences that help to explain both the comorbidity and distinctiveness. Using longitudinal twin data, the present study investigated both the overlapping and distinct relationships between depression and anxiety viewed from the perspective of Gray's Reinforcement Sensitivity Theory (RST): two personality traits of the Behavioral Inhibition and Activation Systems (BIS and BAS).

METHODS

A total of 422 twin pairs (298 monozygotic and 124 dizygotic pairs) participated by completing a personality questionnaire at wave 1, and mood symptoms questionnaires at wave 2. The waves were on average 2.23 years apart.

RESULTS

Multivariate Cholesky decomposition indicated that the genetic variance of the personality traits (BIS and BAS) explained all of the genetic variance in depressive and anxiety symptoms. Additionally, genetic factors related to the BIS positively explained depressive and anxiety symptoms, whereas genetic factors related to the BAS negatively explained only depressive symptoms.

LIMITATIONS

Limitations include shorter time interval and the reliance on self-reported data.

CONCLUSIONS

The present study provided evidence explaining the overlap and differentiation of depressive and anxiety symptoms by using data on personality traits in a longitudinal, genetically-informative design. The findings suggested the personality traits from Gray's RST model played an important role in the prediction, and clarified the description, of both depressive and anxiety symptoms.

Phenotypic and aetiological architecture of depressive symptoms in a Japanese twin sample

BACKGROUND

The phenotypic and aetiological architecture of depression symptomatology has been mostly studied in Western samples. In this study, we conducted a genetically informed factor analysis to elucidate both the phenotypic and aetiological architectures of self-reported depression among a Japanese adult twin sample.

METHODS

Depressive symptoms assessed by Zung's Self-rating Depression Scale were self-rated by 425 twin pairs (301 monozygotic and 124 dizygotic twin pairs) in a community sample in Japan.

RESULTS

An exploratory factor analysis extracted three symptom domains representing cognitive, affective and somatic symptomatology. A confirmatory factor analysis demonstrated that a bi-factor solution fitted better than the alternative solutions, implying that depression may be defined as a combination of a single general construct and three factors specific to each of the three symptom domains. A multivariate genetic analysis with the bi-factor solution showed that the general factor was substantially heritable (47%), and that only the affective symptom domain was significantly heritable (29%) among the three specific factors, their remaining variance being explained by non-shared environmental influences.

CONCLUSIONS

Depression symptomatology appears to be adequately captured by a substantially heritable general factor. The heritability of this factor (47%) in a Japanese adult sample is in line with commonly reported heritability estimates for depression. The three specific factors - cognitive, affective and somatic - are mostly explained by non-shared environmental factors, which include measurement error. The extent to which these specific factors are uniquely associated with correlates of depression when the general factor is accounted for should be investigated in future studies.

The 'affect tagging and consolidation' (ATaC) model of depression vulnerability

Since the 1960's polysomnographic sleep research has demonstrated that depressive episodes are associated with REM sleep alterations. Some of these alterations, such as increased REM sleep density, have also been observed in first-degree relatives of patients and remitted patients, suggesting that they may be vulnerability markers of major depressive disorder (MDD), rather than mere epiphenomena of the disorder. Neuroimaging studies have revealed that depression is also associated with heightened amygdala reactivity to negative emotional stimuli, which may also be a vulnerability marker for MDD. Several models have been developed to explain the respective roles of REM sleep alterations and negatively-biased amygdala activity in the pathology of MDD, however the possible interaction between these two potential risk-factors remains uncharted. This paper reviews the roles of the amygdala and REM sleep in the encoding and consolidation of negative emotional memories, respectively. We present our 'affect tagging and consolidation' (ATaC) model, which argues that increased REM sleep density and negatively-biased amygdala activity are two separate, genetically influenced risk-factors for depression which interact to promote the development of negative memory bias - a well-known cognitive vulnerability marker for depression. Predictions of the ATaC model may motivate research aimed at improving our understanding of sleep dependent memory consolidation in depression aetiology.

Sex differences in the shared genetics of dimensions of self-reported depression and anxiety

BACKGROUND

The prevalence of depression and anxiety symptoms and their comorbidity varies between males and females for reasons still unknown. This study aims to test whether differences between males and females in self-reported symptoms and their covariation are caused by variations in the magnitude of genetic and environmental factors.

METHODS

750 monozygotic and dizygotic healthy twin pairs (18-60 years; M=39.77 years) participated in the TWIN-E project. Univariate and multivariate genetic modelling was undertaken using the Depression Anxiety Stress Scale (DASS-42).

RESULTS

Additive genetics and unique environment contributed to self-reported depression (heritability, h(2): 34%), anxiety (h(2): 30%) and stress (h(2): 34%) scores in univariate models, and to the common latent factor (h(2): 39%) in the multivariate model. No sex differences in magnitude of estimates for DASS-42 scores were found in the univariate model. However when considering correlated depression and anxiety symptomatology only shared genetic factors between depression and anxiety contributed to depression scores in males, but both specific and shared genetic factors contributed to depression scores in females.

LIMITATIONS

The results are limited to the sample of healthy, community, adult, same sex twin pairs who participated in the study.

CONCLUSIONS

Differences in males and females in genetic aetiology of self-reported dimensions of depression are only apparent when taking into consideration the covariation with self-reported anxiety. This difference is highlighted by the finding that both common and specific genetic factors contribute to self-reported depression in females but not males. This novel finding may help explain the increased incidence of depression symptoms in females.

Glutamate cysteine ligase (GCL) and self reported depression: an association study from the HUNT

BACKGROUND

There is increasing evidence suggesting oxidative stress may play a role in the aetiology of depression. Glutathione is the brain's predominant free radical scavenger, and associated polymorphisms of the glutamate cysteine ligase (GCL) gene have been reported for related psychiatric disorders. The aim of the study was to investigate candidate polymorphisms of GCL validated in schizophrenia and their association with current state depression, as measured by the Hospital Anxiety and Depression Scale (HADS).

METHODS

Polymorphisms were genotyped on 983 cases and 967 controls selected from a population sample of adults participating in the Nord-Trøndelag Health Study. Cases were the top scoring individuals (98.5th percentile) on the HADS depression subscale while the controls were randomly selected from below this cut-off. The polymorphisms comprised three SNPs from GCLM, the gene encoding the GCL modifier and 9 SNPs plus a trinucleotide repeat (TNTR) from intron 1 and the 5'UTR of GCLC, the gene encoding the GCL catalytic subunit. Using the linkage disequilibrium between the GCLC markers we also tested whether SNPs could represent the variation of the TNTR.

RESULTS

The candidate polymorphisms showed no evidence for association with depression. The C allele of SNP rs9474592 is coupled with the 9 GAG repeats allele of the TNTR, r²=0.81. None of the other SNPs either individually or as two or three-SNP haplotypes was associated with the TNTR alleles.

LIMITATIONS

Depression was self-reported and measured at one time point.

CONCLUSIONS

This study provides no evidence to suggest that polymorphisms of GCL are associated with self-reported depression.

A population based family study of symptoms of anxiety and depression: the HUNT study

OBJECTIVE

To estimate an upper limit on the heritability of self-reported symptoms of anxiety and depression in a large and population representative nuclear family sample.

METHOD

The ten-item symptom checklist (SCL-10) was administered as part of a health survey in a Norwegian county. The SCL-10 is a shortened version of the SCL-25, assessing symptoms of anxiety and depression. In all, 46,064 people responded, and with data from Statistics Norway, responses of first-degree relatives could be linked. Polychoric correlations between family members score on SCL-10 were calculated, and a structural equation model was fitted to these correlations using the software package R.

RESULTS

All correlations between nuclear family members were in the range of 0.12 to 0.16, indicating small but significant familial influences on SCL-10. In the best fitting model, heritability was estimated at 0.25 (95% CI=0.22-0.27), and sibling specific environmental effects could be discarded.

CONCLUSIONS

The estimated upper level heritability for SCL-10 in our sample was lower than what has been reported in twin studies of similar measures.

Bipolar and major depressive disorder: neuroimaging the developmental-degenerative divide

Both major depressive disorder and bipolar disorder are the subject of a voluminous imaging and genetics literature. Here, we attempt a comprehensive review of MRI and metabolic PET studies conducted to date on these two disorders, and interpret our findings from the perspective of developmental and degenerative models of illness. Elevated activity and volume loss of the hippocampus, orbital and ventral prefrontal cortex are recurrent themes in the literature. In contrast, dorsal aspects of the PFC tend to display hypometabolism. Ventriculomegaly and white matter hyperintensities are intimately associated with depression in elderly populations and likely have a vascular origin. Important confounding influences are medication, phenotypic and genetic heterogeneity, and technological limitations. We suggest that environmental stress and genetic risk variants interact with each other in a complex manner to alter neural circuitry and precipitate illness. Imaging genetic approaches hold out promise for advancing our understanding of affective illness.

Personal Goals of Older Female Twins

This study examined genetic and environmental influences on older women’s personal goals by using data from the Finnish Twin Study on Aging. The interview for the personal goals was completed by 67 monozygotic (MZ) pairs and 75 dizygotic (DZ) pairs. The tetrachoric correlations for personal goals related to health and functioning, close relationships, and independent living were higher in MZ than DZ twins, indicating possible genetic influence. The pattern of tetrachoric correlations for personal goals related to cultural activities, care of others, and physical exercise indicated environmental influence. For goals concerning health and functioning, independent living, and close relationships, additive genetic effect accounted for about half of the individual variation. The rest was the result of a unique environmental effect. Goals concerning physical exercise and care of others showed moderate common environmental effect, while the rest of the variance was the result of a unique environmental effect. Personal goals concerning cultural activities showed unique environmental effects only.

Medically unexplained presentations and quality of life: a study of a predominantly South Asian primary care population in England

Primary care subjects from a predominantly South Asian inner-city setting in Manchester, UK, were studied. We aimed to determine whether medically unexplained symptoms (MUS) are associated with worse health-related quality of life than medically explained symptoms (MES), after controlling for differences in sociodemographic variables, number of somatic symptoms, and levels of anxiety and depression. One hundred nineteen subjects attending general practice completed questionnaires to assess somatic symptoms, anxiety, depression, and quality of life. Doctors' records were later studied to ascertain whether the presentation was medically explained. Thirty-nine subjects (33%) had medically unexplained presentations. Compared to patients with MES, those with MUS had significantly more somatic symptoms (6.9 vs. 4.3, P<.001), higher levels of anxiety (Hospital anxiety and depression scale -- anxiety score) (9.8 vs. 6.7, P=.004), depression (Hospital anxiety and depression scale -- depression) (6.8 vs. 4.5, P=.005), and poorer health-related quality of life (EuroQol standardized score 54.6 vs. 73.3, P=.001). On multiple regression analysis, anxiety, depression, and somatic symptom scores independently (P<.01) predicted quality of life, after controlling for demographic factors. Whether the presentation was medically unexplained or not did not contribute to the regression model (P=.85). Our findings suggest that it is the number of somatic symptoms and the associated anxiety/depression that account for greater impairment in people's health-related quality of life, and not whether they have a medical explanation for their symptoms.

A 4-year follow-up study of syndromal and sub-syndromal anxiety and depression symptoms in the general population: the HUNT study

BACKGROUND

Our aims were to examine the stability of self-rated anxiety and depression symptoms and the predictors for change in case-level status after 4 years in a general population sample.

METHODS

Prospective cohort study. Based on the total score on the Hospital Anxiety and Depression rating scale (HADS-T) in HUNT 2 (1995-1997), three groups were identified: Level 3 (n = 654, score >or= 25 points), Level 2 (n = 654, score 19-24 points), and Level 1 (n = 1,308, score < 19 points). The groups were followed up with a mailed questionnaire after 4 years.

RESULTS

Among the 1,326 (53% response rate) who participated in the follow-up, 816 (62%) had not changed symptom level. The number of participants that had crossed the HADS-T caseness level (19 points) was the same in both directions. In non-cases at baseline (Level 1), lack of friends (OR 2.34, 95% CI 1.28-4.27, P = 0.006) and previous episodes of depression (OR 2.90, 95% CI 1.76-4.78, P < 0.001) predicted HADS-T caseness at follow-up, while higher educational level (OR 0.66, 95% CI 0.46-0.96, P = 0.028) protected from developing caseness level of anxiety and depression. In HADS-T cases (Levels 2 and 3) at baseline, previous episode(s) of depression (OR 0.36, 95% CI 0.19-0.68, P = 0.002) and being unemployed (OR 0.58, 95% CI 0.34-1.00, P = 0.050) predicted HADS-T caseness at follow-up, whereas a higher educational level (OR 1.83, 95% CI 1.24-2.70, P = 0.002) was associated with remission from HADS-T caseness after 4 years.

CONCLUSIONS

Though symptom fluctuation was considerable, conventional HADS-T caseness (>or=19 points) was a reliable and valid predictor for high long-term symptom stability of anxiety and depression in our general population sample.

Return of depressed men: changes in distribution of depression and symptom cases in Norway between 1990 and 2001

BACKGROUND

Women's elevated risk of depression compared to men is a common finding in psychiatric epidemiology. Studies conducted in the 1950s and 1970s, however, documented approximately equal prevalence of sex rates.

AIM

This study investigated changes in depression rates between 1990 and 2001 in Norway. Further, differences in severity were examined between men and women.

METHOD

A study population (later to be called OsLof) was established in 1990, supplemented in 2001, and analysed as two cross-sectional datasets to compare sex and age differences in ICD-10 diagnoses and HSCL-25> or =1.75 caseness. Organic depression and the DSM-IV Major Depressive Episode were also examined in 2001.

RESULTS

There was no significant change in the prevalence of depression or HSCL-25 caseness from 1990 to 2001. However, a major shift in prevalence occurred over time within the 18-34 year old age category with significantly higher rates among younger men (1% to 10%) and lowered rates among younger women (10% to 4%). Among persons depressed, no significant differences were found for severity between the sexes.

LIMITATIONS

A selection of healthier participants than found in the source population might have resulted in lower prevalence than real.

CONCLUSION

There was no indication of an overall increase in depression from 1990 to 2001, neither by diagnosis nor by symptom checklist scores. However, a major shift in prevalence occurred within the 18-34 year old age category with significantly higher rates among younger men and lowered rates among younger women. No sex differences existed in terms of severity of depression.

Length of gestation and depressive symptoms at age 60 years

BACKGROUND

A non-optimal foetal environment, reflected in smaller birth size and shorter duration of gestation, is a risk factor for compromised health later in life.

AIMS

To examine whether smaller birth size and shorter gestation predict depressive symptoms.

METHOD

A total of 1371 members of a cohort born between 1934 and 1944 at term (259-294 days'gestation) in Helsinki, Finland, completed the Beck Depression Inventory (BDI) and the Center for Epidemiological Studies Depression scale (CES-D) at an average age of 61.5 years (BDI) and 63.4 years (BDI and CES-D).

RESULTS

Gestational length predicted depressive symptoms linearly and independently of gender and birth weight: per day decrease in gestational length, depressive symptoms scores increased by 0.8-0.9% (95% CI 0.2-1.4, P<0.009). Weight, length and head circumference at birth showed no linear association with depression, adjusted for gender and gestational length. The results did not change when further controlled for socio-economic characteristics at birth and in adulthood, age and body mass index in adulthood.

CONCLUSIONS

Susceptibility to depressive symptoms may relate to shorter length of gestation.

Genetic and environmental contributions to depressive personality disorder in a population-based sample of Norwegian twins

BACKGROUND

Depressive personality disorder (DPD) was introduced in DSM-IV as a new category requiring further study. The aim of this study was to estimate genetic and environmental contributions to DPD in a population-based twin sample, and include data on criteria performance, prevalence and diagnostic overlap.

METHODS

Axis I and Axis II diagnoses were obtained by structured interviews in a population-based sample of 2794 young adult twins. Statistical analyses included correlation and factor analysis based on polychoric correlation coefficients, and diagnostic overlap applying adjusted odds ratios. Contributions from additive genetic and common and unique environmental influences to the liability to DPD were computed using structural equation modelling, applying a multiple threshold variable.

RESULTS

Liability to DPD could best be explained by additive genetic and unique environmental factors, with heritability estimates of 49% (95% CI 0.41-0.57) in females and 25% (95% CI 0.12-0.40) in males. The best-fitting model indicated that some of the genes contributing to DPD differ between men and women. Chronbach's alpha was 0.87. 2.0% of participants fulfilled the criteria for DPD, and overlap was most pronounced for dysthymic disorder and avoidant personality disorder.

LIMITATIONS

Low prevalence rates and subsequent inclusion of subthreshold criteria could have influenced parameter estimates, especially in males.

CONCLUSIONS

DPD was almost twice as heritable in females as in males, comparable to previous studies on major depression. The proposed criteria showed good measurement properties, and DPD was not completely subsumed within any other disorder.

Estimating genetic and environmental influences on depressive symptoms in adolescence: differing effects on higher and lower levels of symptoms

We estimate the relative effect sizes of genetic and environmental influences on both higher and lower levels of depressive symptoms with attention to persistence over a 1-year period in the genetically informative subsample of adolescents participating in the National Longitudinal Study of Adolescent Health (Add Health). Shared environmental effects were significant for persistent higher levels of depressive symptoms but not nonpersistent symptoms. Genetic effects were significant for both persistent and nonpersistent lower levels of depressive symptoms. Nongenetic factors that promote similarity between siblings for high levels of depressive symptoms are important and should be considered in both etiological and applied research. Genetic contributions to lack of susceptibility to depression should be considered in biological models of depression suppression.

Whole genome linkage scan of recurrent depressive disorder from the depression network study

Genome-wide linkage analysis was carried out in a sample of 497 sib pairs concordant for recurrent major depressive disorder (MDD). There was suggestive evidence for linkage on chromosome 1p36 where the LOD score for female-female pairs exceeded 3 (but reduced to 2.73 when corrected for multiple testing). The region includes a gene, MTHFR, that in previous studies has been associated with depressive symptoms. Two other regions, on chromosomes 12q23.3-q24.11 and 13q31.1-q31.3, showed evidence for linkage with a nominal P < 0.01. The 12q peak overlaps with a region previously implicated by linkage studies of unipolar and bipolar disorders and contains a gene, DAO, that has been associated with both bipolar disorder and schizophrenia. The 13q peak lies within a region previously linked strongly to panic disorder. A fourth modest peak with an LOD of greater than 1 on chromosome 15q lies within a region that showed genome-wide significant evidence of a recurrent depression locus in a previous sib-pair study. Both the 12q and the 15q findings remained significant at genome-wide level when the data from the present study and the previous reports were combined.

The Depression Network (DeNT) Study: methodology and sociodemographic characteristics of the first 470 affected sibling pairs from a large multi-site linkage genetic study

BACKGROUND

The Depression Network Study (DeNt) is a multicentre study designed to identify genes and/or loci linked to and/or associated with susceptibility to unipolar depression in Caucasian families. This study presents the method and socio-demographic details of the first 470 affected sibling pairs recruited from 8 different sites in Europe and the United States of America.

METHODS

Probands fulfilling either the Diagnostic and Statistical Manual 4th edition (DSM-IV) or the International Classification of Diseases 10th edition (ICD-10) criteria for recurrent unipolar depression of moderate or severe degree and who had at least one similarly affected sibling were eligible for the study. Detailed clinical and psychological assessments were undertaken on all subjects including an interview using the Schedules for Clinical Assessment in Neuropsychiatry. Blood samples were collected from all participants to extract DNA for linkage analysis.

RESULTS

The different sites used different recruitment strategies depending on local health care organisation but despite this there was remarkable similarity across sites for the subjects recruited. Although the Bonn site had significantly older subjects both for age of onset and age at interview, for the sample as a whole, subjects were interviewed in their mid-40s and had experienced the onset of their recurrent depression in their 20s. Preliminary genome screening was able to include 929 out of the 944 subjects (98.4%) typed at 932 autosomal and 544 X chromosome markers.

CONCLUSIONS

This paper describes the methodology and the characteristics of the subjects from the 414 families included in the first wave of genotyping from the multi-site DeNT study. Ultimately the study aims to collect affected sibling pairs from approximately 1200 families.