Cardiff depression study. A sib-pair study of life events and familiality in major depression

The Cannabis-Induced Epigenetic Regulation of Genes Associated with Major Depressive Disorder

The prevalence of depression is increasing worldwide, as is the number of people suffering from treatment-resistant depression; these patients constitute 30% of those treated. Unfortunately, there have not been significant advances in the treatment of this disorder in the past few decades. Exposure to cannabis and cannabis-derived compounds impacts depression symptomatology in different ways, with evidence indicating that cannabidiol has antidepressant effects; there have been mixed results with medical cannabis. Even though the exact molecular mechanisms of the action underlying changes in depression symptomatology upon exposure to cannabis and cannabis-derived compounds are still unknown, there is strong evidence that these agents have a widespread impact on epigenetic regulation. We hypothesized that exposure to cannabis or cannabis-derived compounds changes the DNA methylation levels of genes associated with depression. To test this hypothesis, we first performed a literature search to identify genes that are differentially methylated upon exposure to cannabis and cannabis-derived compounds, as reported in methylome-wide association studies. We next checked whether genes residing in loci associated with depression, as identified in the largest currently available genome-wide association study of depression, were reported to be epigenetically regulated by cannabis or cannabis-related compounds. Multiple genes residing in loci associated with depression were found to be epigenetically regulated by exposure to cannabis or cannabis-derived compounds. This epigenomic regulation of depression-associated genes by cannabis or cannabis-derived compounds was reported across diverse organisms, tissues, and developmental stages and occurred in genes crucial for neuronal development, functioning, survival, and synapse functioning, as well as in genes previously implicated in other mental disorders.

Adiposity and Smoking Mediate the Relationship Between Depression History and Inflammation Among Young Adults

BACKGROUND

Depression is associated with inflammation, but the mechanisms underlying this association are unclear. We examined adiposity and smoking as potential pathways through which childhood depression may lead to an elevated inflammatory status among young adults.

METHODS

The sample included 294 subjects with histories of depression (probands), 270 never-depressed siblings of probands (high-risk siblings), and 169 controls. C-reactive protein (CRP), interleukin-6 (IL-6), and soluble intercellular adhesion molecule-1 (sICAM-1) were assessed in serum samples. An adiposity score was computed from body mass index and waist circumference. Smoking behavior was evaluated during an interview. Mixed-effects models were used to test whether adiposity and smoking mediate the relationship between depression and inflammation.

RESULTS

Probands (p = .004), but not siblings (p = .071), had higher levels of sICAM-1 compared to controls. However, depression history and risk status had no direct effects on CRP (ps > .13) or IL-6 (ps > .16). Importantly, adiposity indirectly mediated the effect of group (probands vs. controls; siblings vs. controls) on all three inflammatory markers. Smoking indirectly mediated the effect of group (probands vs. controls; siblings vs. controls) on sICAM-1 only.

CONCLUSIONS

Among young adults, the adverse inflammatory consequences of depression history are significant for sICAM-1. Adiposity and smoking are pathways through which depression can indirectly impact several inflammatory markers, suggesting possible preventive interventions to improve the immunologic and cardiovascular health of depression-prone individuals.

DNA methylation of the KLK8 gene in depression symptomatology

Background

Depression is a common, complex, and debilitating mental disorder estimated to be under-diagnosed and insufficiently treated in society. Liability to depression is influenced by both genetic and environmental risk factors, which are both capable of impacting DNA methylation (DNAm). Accordingly, numerous studies have researched for DNAm signatures of this disorder. Recently, an epigenome-wide association study of monozygotic twins identified an association between DNAm status in the KLK8 (neuropsin) promoter region and severity of depression symptomatology.

Methods

In this study, we aimed to investigate: (i) if blood DNAm levels, quantified by pyrosequencing, at two CpG sites in the KLK8 promoter are associated with depression symptomatology and depression diagnosis in an independent clinical cohort and (ii) if KLK8 DNAm levels are associated with depression, postpartum depression, and depression symptomatology in four independent methylomic cohorts, with blood and brain DNAm quantified by either MBD-seq or 450 k methylation array.

Results

DNAm levels in KLK8 were not significantly different between depression cases and controls, and were not significantly associated with any of the depression symptomatology scores after correction for multiple testing (minimum p value for KLK8 CpG1 = 0.12 for ‘Depressed mood,’ and for CpG2 = 0.03 for ‘Loss of self-confidence with other people’). However, investigation of the link between KLK8 promoter DNAm levels and depression-related phenotypes collected from four methylomic cohorts identified significant association (p value < 0.05) between severity of depression symptomatology and blood DNAm levels at seven CpG sites.

Conclusions

Our findings suggest that variance in blood DNAm levels in KLK8 promoter region is associated with severity of depression symptoms, but not depression diagnosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13148-021-01184-5.

Gene expression profiling in peripheral blood lymphocytes for major depression: preliminary cues from Chinese discordant sib-pair study

The etiology of major depressive disorder (MDD) involves many factors such as heredity and environment. There are very few MDD-related studies in Chinese population using twin or sib-pairs for depression-control samples. Here we used the microarray approach and compared gene expression profiling of peripheral blood lymphocytes from 6 sib-pairs discordant on lifetime history of MDD. Within sib-pair differentially expressed genes are obvious fewer in the 1st, 2nd, and 5th compared with those in the 3rd, 4th, and 6th sib-pairs. Gene expression pattern of these DEGs distinguished MDD individuals from the normal one in 3rd, 4th, and 6th sib-pair but not in the 1st, 2nd, and 5th pair, suggesting heterogeneity of different sib-pairs and somewhat commonalities among the 3rd, 4th, and 6th sib-pairs. Comprehensive protein interaction network analysis revealed two key genes PTH and FGF2 in a dominant network where the majority of the genes were significantly down-regulated. PTH was significantly down-regulated in all the sib-pairs while FGF2 was in the 3rd, 4th, and 6th sib-pairs. KEGG enrichment analysis of all the DEGs in networks showed that PTH and related genes were significantly enriched in the pathway of parathyroid hormone secretion, synthesis, and action while FGF2 and related genes were significantly enriched in the pathways of cancer and specifically breast cancer. Generally reduced expression of these genes in peripheral blood lymphocytes of MDD individuals implied their functional repression associated with MDD. Pending validation in more samples, the findings in this study provided valuable cues for understanding the potential mechanism of MDD, as well as potential markers for the diagnosis and treatment of depression in the Chinese population.

Familial aggregation of depression, but no familial aggregation of individual depressive symptoms

Background

Familial aggregation of major depression might indicate a genetic liability for the disorder. The complete disorder or, alternatively, only some individual symptoms might be inherited. Under the latter condition, an increased frequency of inherited symptoms might consecutively increase the likelihood to reach the threshold for depression in relatives and, thus, might cause the familial aggregation of depression. Up to now, no study investigated the possibility of a relationship between individual depressive symptoms and the familial aggregation of depression.

Methods

The familial aggregation of early-onset depression (age-at-onset < 60 years, EOD) but less so of late-onset depression (LOD) has been shown in this sample. To assess the hypothesis of an inheritance of individual depressive symptoms as a possible cause of the familial aggregation of depression, frequencies of symptoms were compared in relatives of depressed patients and of controls using forward logistic regression analyses.

Results

Some individual depressive symptoms showed clustering in relatives of patients with depression, but the pattern of inheritance was inconsistent, i.e. the clustering of symptoms was different between non-depressed and depressed relatives of patients with EOD and LOD, respectively. No intra-familial clustering of specific depressive symptoms within families of depressed subjects could be observed.

Conclusions

Due to the inconsistencies in the clustering of individual symptoms in non-depressed and depressed relatives and the lack of intra-familial clustering, the familial aggregation of depression is unlikely to be caused by the aggregation of individual depressive symptoms. An inheritance of the vulnerability for complete depressive disorders influenced by environmental factors is more likely.

Risk of Depression in the Offspring of Parents with Depression: The Role of Emotion Regulation, Cognitive Style, Parenting and Life Events

Children of depressed parents are at heightened risk for developing depression, yet relatively little is known about the specific mechanisms responsible. Since preventive interventions for this risk group show small effects which diminish overtime, it is crucial to uncover the key risk factors for depression. This study compared various potential mechanisms in children of depressed (high-risk; n = 74) versus non-depressed (low-risk; n = 37) parents and explored mediators of parental depression and risk in offspring. A German sample of N = 111 boys and girls aged 8 to 17 years were compared regarding children's (i) symptoms of depression and general psychopathology, (ii) emotion regulation strategies, (iii) attributional style, (iv) perceived parenting style and (v) life events. Children in the high-risk group showed significantly more symptoms of depression and general psychopathology, less adaptive emotion regulation strategies, fewer positive life events and fewer positive parenting strategies in comparison with the low-risk group. Group differences in positive and negative attributional style were small and not statistically significant in a MANOVA test. Maladaptive emotion regulation strategies and negative life events were identified as partial mediators of the association between parental depression and children's risk of depression. The study highlights the elevated risk of depression in children of depressed parents and provides empirical support for existing models of the mechanisms underlying transmission. Interestingly, the high-risk group was characterised by a lack of protective rather than increased vulnerability factors. These results are crucial for developing more effective preventive interventions for this high-risk population.

Cardiac vagal control mediates the relation between past depression and blood pressure several years later among young adults

Depression has been associated with high blood pressure (BP). However, the mechanisms of the relation between depression and high BP are unclear. We therefore examined whether impaired cardiac vagal control, indexed as low levels of resting respiratory sinus arrhythmia (RSA), serves as a route from depression to high BP. The sample included 125 subjects with histories of depression (probands), 123 never depressed siblings of probands (high-risk siblings), and 156 controls. Resting RSA was assessed at Time 1 (T1) along with BP when subjects were adolescents (M_age  = 16.3 years); systolic and diastolic BP (SBP and DBP) were measured again at Time 2 (T2) when subjects were young adults (M_age  = 22.3 years). Linear mixed-effects models were used to examine the group differences in resting RSA and T2 BP outcomes and to test for RSA mediation of the relation between depression (history or being at high risk) and BP. Resting RSA was lower among probands than controls but was similar among high-risk siblings and controls, while the subject groups did not differ in T2 SBP or DBP. Controlling for T1 BP, depression history indirectly affected T2 DBP (but not SBP) through resting RSA. The findings suggest that, although the direct detrimental effects of depression on BP are not yet evident in young adulthood, among those with depression histories, impaired cardiac vagal control appears to serve as a mechanism of elevated DBP.

Epigenome-wide association study of depression symptomatology in elderly monozygotic twins

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^-7) and DAZ associated protein 2 (DAZAP2, p-value = 3.13 × 10^-8) genes. Other top associated probes were located in gene bodies of MAD1L1 (p-value = 5.16 × 10^-6), SLC29A2 (p-value = 6.15 × 10^-6) and AKT1 (p-value = 4.47 × 10^-6), 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.

Network Analysis of Depression-Related Transcriptomic Profiles

Major depressive disorder is a common debilitating disorder that is associated with increased morbidity and mortality. However, the molecular mechanism underlying depression remains largely unknown. The current study investigated the association of depression with blood gene expression using data from the Alzheimer's Disease Neuroimaging Initiative (ADNI). Depression was measured by the geriatric depression scale, and the blood gene expression was measured by the Affymetrix Human Genome U219 Array. Linear regression was used to test the association between gene expression and depression, and the model was adjusted for age and sex. A total of 671 participants were included in our study (mean age 75 ± 8 years, 43.2% women). We found three genes were associated with depression, including COL1A2 (P = 8.9 × 10^-8), RNF150 (P = 1.4 × 10^-7) and CTGF (P = 8.3 × 10^-7). An interaction network was built, and the pathway analysis indicated that many depression-related genes were involved in the neurotrophin signaling pathway (P = 2.1 × 10^-7). Future studies are necessary to validate our findings and further investigate potential mechanism of depression.

The impact of trauma exposure on the development of PTSD and psychological distress in a volunteer fire service

Emergency service workers (ESWs) are at increased risk of trauma-related mental disorders. However, volunteer ESWs, who comprise the majority of firefighters in Western countries, have limited access to the necessary support services for mental health problems. This study aimed to examine the impact of the level and types of trauma exposure on the development of mental disorders in a volunteer fire service. Members of an Australian volunteer fire service (N = 459) completed a cross-sectional survey. Information on the number and types of distressing critical incidents involved within the last year was collected. Validated, self-report measures were used to determine probable post-traumatic stress disorder (PTSD) and psychological distress caseness. The risk of probable PTSD was significantly higher for those with the most frequent involvement with distressing incidents and the highest levels of cumulative trauma exposure. Being trapped in a dangerous situation or being assaulted by other people, resulted in the greatest odds of developing a mental disorder. Volunteer fire service members with the highest levels of trauma exposure and involvement with particular types of critical incidents are at elevated risk of mental health problems. The implications for the provision of psychological support measures amongst volunteer emergency services are discussed.

Psychological status and coping styles of caregivers of individuals with intellectual disability and psychiatric illness

BACKGROUND

The psychological status of caregivers of individuals with intellectual disability and psychiatric illness (PI) is important for effective management. The aim of this study was to examine the psychological status and its relationship with coping styles among these caregivers.

MATERIALS & METHODS

Caregivers (N = 80) of individuals with intellectual disability (n = 40) and PI (n = 40) were administered a socio-demographic questionnaire, depression, anxiety and stress scale and COPE Inventory.

RESULTS

Caregivers experienced depression, anxiety and stress symptoms. These symptoms were found to be significantly higher among caregivers of individuals with intellectual disability than those with PI. The most common coping style used was religious coping. Use of positive reinterpretation and growth was associated with lower levels of depression and stress symptoms.

CONCLUSION

Caregivers' mental health plays an important role in the quality of care delivery and outcome. Use of appropriate coping styles can reduce the impact of these symptoms.

The mental health of fire-fighters: An examination of the impact of repeated trauma exposure

OBJECTIVE

Emergency workers, such as fire-fighters, are routinely exposed to potentially traumatic events. While a number of studies have examined the occurrence of post-traumatic stress disorder, the role of multiple traumas on other mental health sequelae, such as depression and alcohol misuse, among emergency workers remains unclear. This study aimed to assess the prevalence of post-traumatic stress disorder, depression and alcohol misuse in a sample of current and retired fire-fighters and examine their relationship with cumulative trauma exposure.

METHOD

A cross-sectional survey was completed by current (n = 488) and retired (n = 265) fire-fighters from Fire and Rescue New South Wales, Australia. Demographic and occupational information was collected, including the number of fatal incidents fire-fighters reported attending across years of service. Validated, self-report measures were used to determine probable caseness for post-traumatic stress disorder, depression and heavy drinking.

RESULTS

Among current fire-fighters, rates of post-traumatic stress disorder and depression were 8% and 5%, respectively, while 4% reported consumption of more than 42 alcoholic drinks per week. Retired fire-fighters reported significantly greater levels of symptomatology, with the prevalence estimates of post-traumatic stress disorder at 18% (p = 0.001), depression at 18% (p < 0.001) and heavy drinking at 7%. There was a significant positive linear relationship between the number of fatal incidents attended and rates of post-traumatic stress disorder, depression and heavy drinking.

CONCLUSION

Fire-fighters suffer from high rates of mental disorders, with rates of post-traumatic stress disorder, depression and heavy drinking continuing to rise in a linear manner with each additional trauma exposure. The level of psychiatric morbidity among retired fire-fighters appears to be particularly high. Our findings have important implications for the ongoing debates surrounding the detection of mental disorders in high-risk occupations and for policy considerations around the welfare of current and retired emergency workers.

Positive Affectivity is Dampened in Youths with Histories of Major Depression and Their Never-Depressed Adolescent Siblings

While hedonic capacity is diminished during clinical depression, it is unclear whether that deficit constitutes a risk factor and/or persists after depression episodes remit. To examine these issues, adolescents with current/past major depression (probands; n=218), never depressed biological siblings of probands (n=207), and emotionally-well controls (n=183) were exposed to several positively valenced probes. Across baseline and hedonic probe conditions, controls consistently reported higher levels of positive affect than high-risk siblings, and siblings reported higher levels of positive affect than probands (remitted and depressed probands' reports were similar). Extent of positive affect across the protocol predicted adolescents' self-reports of social support network and parental reports of offspring's use of various adaptive mood repair responses in daily life. Attenuated hedonic responding among youths remitted from depression offers partial support for anhedonia as a trait, while its presence among never depressed high-risk siblings argues for anhedonia as a potential diathesis for clinical depression.

Phenotypic Association Analyses With Copy Number Variation in Recurrent Depressive Disorder

BACKGROUND

Defining the molecular genomic basis of the likelihood of developing depressive disorder is a considerable challenge. We previously associated rare, exonic deletion copy number variants (CNV) with recurrent depressive disorder (RDD). Sex chromosome abnormalities also have been observed to co-occur with RDD.

METHODS

In this reanalysis of our RDD dataset (N = 3106 cases; 459 screened control samples and 2699 population control samples), we further investigated the role of larger CNVs and chromosomal abnormalities in RDD and performed association analyses with clinical data derived from this dataset.

RESULTS

We found an enrichment of Turner's syndrome among cases of depression compared with the frequency observed in a large population sample (N = 34,910) of live-born infants collected in Denmark (two-sided p = .023, odds ratio = 7.76 [95% confidence interval = 1.79-33.6]), a case of diploid/triploid mosaicism, and several cases of uniparental isodisomy. In contrast to our previous analysis, large deletion CNVs were no more frequent in cases than control samples, although deletion CNVs in cases contained more genes than control samples (two-sided p = .0002).

CONCLUSIONS

After statistical correction for multiple comparisons, our data do not support a substantial role for CNVs in RDD, although (as has been observed in similar samples) occasional cases may harbor large variants with etiological significance. Genetic pleiotropy and sample heterogeneity suggest that very large sample sizes are required to study conclusively the role of genetic variation in mood disorders.

Evaluation of psychiatric and genetic risk factors among primary relatives of suicide completers in Delhi NCR region, India

Suicide as a public health problem is studied worldwide and association of psychiatric and genetic risk factors for suicidal behavior are the point of discussion in studies across different ethnic groups. The present study is aimed at evaluating psychiatric and genetic traits among primary relatives of suicide completer families in an urban Indian population. Bi-variate analysis shows significant increase in major depression (PHQ and Hamilton), stress, panic disorder, somatoform disorder and suicide attemptamong primary compared to other relatives. Sib pair correlations also reveal significant results for major depression (Hamilton), stress, suicide attempt, intensity of suicide ideation and other anxiety syndrome. 5-HTTLPR, 5-HTT (Stin2) and COMT risk alleles are higher among primary relatives, though statistically insignificant. Backward conditional logistic regression analysis show only independent variable, Depression (Hamilton) made a unique statistically significant contribution to the model in primary relatives.

Illness progression, recent stress, and morphometry of hippocampal subfields and medial prefrontal cortex in major depression

BACKGROUND

Longitudinal studies of illness progression in patients with major depressive disorder (MDD) indicate that the onset of subsequent depressive episodes becomes increasingly decoupled from external stressors. A possible mechanism underlying this phenomenon is that multiple episodes induce long-lasting neurobiological changes that confer increased risk for recurrence. Prior morphometric studies have frequently reported volumetric reductions in patients with MDD--especially in medial prefrontal cortex (mPFC) and the hippocampus--but few studies have investigated whether these changes are exacerbated by prior episodes.

METHODS

In a sample of 103 medication-free patients with depression and control subjects with no history of depression, structural magnetic resonance imaging was performed to examine relationships between number of prior episodes, current stress, hippocampal subfield volume and cortical thickness. Volumetric analyses of the hippocampus were performed using a recently validated subfield segmentation approach, and cortical thickness estimates were obtained using vertex-based methods. Participants were grouped on the basis of the number of prior depressive episodes and current depressive diagnosis.

RESULTS

Number of prior episodes was associated with both lower reported stress levels and reduced volume in the dentate gyrus. Cortical thinning of the left mPFC was associated with a greater number of prior depressive episodes but not current depressive diagnosis.

CONCLUSIONS

Collectively, these findings are consistent with preclinical models suggesting that the dentate gyrus and mPFC are especially vulnerable to stress exposure and provide evidence for morphometric changes that are consistent with stress-sensitization models of recurrence in MDD.

The one-carbon-cycle and methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism in recurrent major depressive disorder; influence of antidepressant use and depressive state?

BACKGROUND

An important biological factor suggested in the pathophysiology of (recurrent) Major Depressive Disorder (MDD) concerns a polymorphism in a gene encoding for the MTHFR-enzyme of the one-carbon (1-C)-metabolism. Integratively investigating key 1-C-components (folate, homocysteine, vitamin B6 and B12), including the possible effects of antidepressant medication and depressive state, could provide more insight in the possible association between the MTHFR-polymorphism and recurrent MDD.

METHODS

We compared the MTHFR C677T-polymorphism together with the key 1-C-components in clinically ascertained patients with recurrent MDD (n=137) to age- and gender-matched healthy controls (n=73).

RESULTS

First, patients had lower folate (t=2.25; p=.025) as compared to controls; a difference that resolved after correction for demographics (t=1.22; p=.223). Second, patients that were depressed during sampling had lower vitamin B6 (t=-2.070; p=.038) and higher homocysteine (t=2.404; p=.016) compared to those in remission. Finally, current use of antidepressants had no influence on the 1-C-components.

CONCLUSIONS

Despite investigation of a specific recurrently depressed patient population, we found no clear associations with the 1-C-cycle, except for higher homocysteine and lower vitamin B6 during the depressed state. This suggests that 1-C-cycle alterations in MDD are state-associated, possibly resulting from high levels of acute (psychological) stress, and may provide a treatment target to reduce cardiovascular risk in this population.

Gene environment interaction studies in depression and suicidal behavior: An update

Increasing evidence supports the involvement of both heritable and environmental risk factors in major depression (MD) and suicidal behavior (SB). Studies investigating gene-environment interaction (G × E) may be useful for elucidating the role of biological mechanisms in the risk for mental disorders. In the present paper, we review the literature regarding the interaction between genes modulating brain functions and stressful life events in the etiology of MD and SB and discuss their potential added benefit compared to genetic studies only. Within the context of G × E investigation, thus far, only a few reliable results have been obtained, although some genes have consistently shown interactive effects with environmental risk in MD and, to a lesser extent, in SB. Further investigation is required to disentangle the direct and mediated effects that are common or specific to MD and SB. Since traditional G × E studies overall suffer from important methodological limitations, further effort is required to develop novel methodological strategies with an interdisciplinary approach.

Interaction between a serotonin transporter gene promoter region polymorphism and stress predicts depressive symptoms in Chinese adolescents: a multi-wave longitudinal study

BACKGROUND

The serotonin transporter (5-HTT) gene may play an important role in the onset and development of mental disorders. Past studies have tested whether a functional polymorphism in the 5-HTT gene linked promoter region (5-HTTLPR) moderated the association between stress and depressive symptoms, but the results of these studies were inconsistent. Thus, the aim of the current study was to examine the interaction between 5-HTTLPR and stress that predict depressive symptoms in Chinese adolescents.

METHODS

A total of 252 healthy adolescents (131 females and 121 males, aged from 14 to 18, mean = 16.00, standard deviation = 0.60) participated in this study. During the initial assessment, all participants completed the Center for Epidemiological Studies Depression Scale (CES-D) and Adolescent Life Events Questionnaire (ALEQ) and were genotyped for the 5-HTTLPR polymorphism. Participants subsequently completed CES-D and ALEQ once every three months during the subsequent 24 months. A multilevel model was used to investigate the 5-HTTLPR × stress interaction in predicting depressive symptoms.

RESULTS

The results indicated no main effect of 5-HTTLPR and a significant 5-HTTLPR × stress interaction in females only. Females with at least one 5-HTTLPR S allele exhibited more depressive symptoms under stressful situations. No significant 5-HTTLPR × stress interaction was found in males.

CONCLUSIONS

In Chinese adolescents, there are gender differences on the interaction between 5-HTTLPR and stress that predict depressive symptoms. The association between stress and depressive symptoms is moderated by 5-HTTLPR in Chinese female adolescents.

A genome-wide association study of depressive symptoms

BACKGROUND

Depression is a heritable trait that exists on a continuum of varying severity and duration. Yet, the search for genetic variants associated with depression has had few successes. We exploit the entire continuum of depression to find common variants for depressive symptoms.

METHODS

In this genome-wide association study, we combined the results of 17 population-based studies assessing depressive symptoms with the Center for Epidemiological Studies Depression Scale. Replication of the independent top hits (p<1×10(-5)) was performed in five studies assessing depressive symptoms with other instruments. In addition, we performed a combined meta-analysis of all 22 discovery and replication studies.

RESULTS

The discovery sample comprised 34,549 individuals (mean age of 66.5) and no loci reached genome-wide significance (lowest p = 1.05×10(-7)). Seven independent single nucleotide polymorphisms were considered for replication. In the replication set (n = 16,709), we found suggestive association of one single nucleotide polymorphism with depressive symptoms (rs161645, 5q21, p = 9.19×10(-3)). This 5q21 region reached genome-wide significance (p = 4.78×10(-8)) in the overall meta-analysis combining discovery and replication studies (n = 51,258).

CONCLUSIONS

The results suggest that only a large sample comprising more than 50,000 subjects may be sufficiently powered to detect genes for depressive symptoms.

Homozygosity mapping of depressive disorder in a large family from Pakistan: significant linkage on chromosome 6 and 9

A large family with a high prevalence of recurrent major depression and high average inbreeding coefficient was ascertained from rural Pakistan. Subjects were interviewed and diagnosed by a trained psychiatrist, 370 microsatellite markers were genotyped and the program FEstim was used for homozygosity mapping. Significant linkage was found on Chromosome 9 and Chromosome 6 after fine mapping. These regions on Chromosome 6 and 9 may harbor genes which predispose to depression.

Genome-wide association analysis of copy number variation in recurrent depressive disorder

Large, rare copy number variants (CNVs) have been implicated in a variety of psychiatric disorders, but the role of CNVs in recurrent depression is unclear. We performed a genome-wide analysis of large, rare CNVs in 3106 cases of recurrent depression, 459 controls screened for lifetime-absence of psychiatric disorder and 5619 unscreened controls from phase 2 of the Wellcome Trust Case Control Consortium (WTCCC2). We compared the frequency of cases with CNVs against the frequency observed in each control group, analysing CNVs over the whole genome, genic, intergenic, intronic and exonic regions. We found that deletion CNVs were associated with recurrent depression, whereas duplications were not. The effect was significant when comparing cases with WTCCC2 controls (P=7.7 × 10(-6), odds ratio (OR) =1.25 (95% confidence interval (CI) 1.13-1.37)) and to screened controls (P=5.6 × 10(-4), OR=1.52 (95% CI 1.20-1.93). Further analysis showed that CNVs deleting protein coding regions were largely responsible for the association. Within an analysis of regions previously implicated in schizophrenia, we found an overall enrichment of CNVs in our cases when compared with screened controls (P=0.019). We observe an ordered increase of samples with deletion CNVs, with the lowest proportion seen in screened controls, the next highest in unscreened controls and the highest in cases. This may suggest that the absence of deletion CNVs, especially in genes, is associated with resilience to recurrent depression.

Affective intensity and lability: heritability in adult male twins

BACKGROUND

Inability to monitor and self-regulate heightened levels of affect lability and affect intensity is associated with a range of mood, anxiety, and personality disorders, psychosomatic symptoms and socially maladaptive behaviors. Despite the importance of these aspects of affective regulation, there are no twin study data to shed light on the genetic and environmental components of these constructs.

METHODS

Affective Lability Scale (ALS) and Affect Intensity Measure (AIM) questionnaires were administered to 796 male twins in the Vietnam Era Twin Registry and subjected to twin and model-fitting analyses. Complete data were available from 182 monozygotic and 119 dizygotic twin pairs.

RESULTS

Biometrical genetic model-fitting estimates indicated that additive genetic influence accounted for 40% of the variance in affect intensity and 25% of the variance in the ALS subscale assessing anxiety-depression mood shifts. Nonadditive genetic influence was indicated for ALS subscales measuring shifts between normal mood and depression (29%) and anger (27%), respectively. There was negligible evidence of shared environmental influence on affect measures. In contrast, estimates of nonshared environmental influences ranged from 52% to 74%.

LIMITATIONS

Female were not included in this study due to the nature of the twin cohort. Data from subjects in a population cohort may not generalize to clinical populations. Measures of environment were not included.

CONCLUSIONS

These results provide evidence for moderate heritability of affect intensity and specific measures of affect lability. Individual differences in mood regulation may represent phenotypic variation in a core psychobiologic vulnerability (e.g., neurotransmitter systems).

The genetic basis of depression

Since the publication of the working draft of the human genome just over a decade ago, there have been dramatic advances in our understanding of the role genetics play in both normal human functioning as well as in disease. The identification of genes, which influence an individual's susceptibility to depression, is not only an intriguing scientific endeavour in its own right, but further, if a gene can be confidently implicated in depression, then this could shed light on the aetiological processes involved in the disease. Moreover, a genetic association with depression may identify targets for consideration in the development of novel treatments for the illness. This chapter will summarise the current research into the genetic basis of depression. A number of genes of interest have been highlighted, although a genetic variant, that is unequivocally associated with increased risk for the disease, is yet to be identified. However, technologies and methodologies are evolving rapidly, and genetic approaches have helped shape how we conceptualise depression as an illness.

Life stress and kindling in bipolar disorder: review of the evidence and integration with emerging biopsychosocial theories

Most life stress literature in bipolar disorder (BD) fails to account for the possibility of a changing relationship between psychosocial context and episode initiation across the course of the disorder. According to Post's (1992) influential kindling hypothesis, major life stress is required to trigger initial onsets and recurrences of affective episodes, but successive episodes become progressively less tied to stressors and may eventually occur autonomously. Subsequent research on kindling has largely focused on unipolar depression (UD), and the model has been tested in imprecise and inconsistent ways. The aim of the present paper is to evaluate evidence for the kindling model as it applies to BD. We first outline the origins of the hypothesis, the evidence for the model in UD, and the issues needing further clarification. Next, we review the extant literature on the changing relationship between life stress and bipolar illness over time, and find that evidence from the methodologically strongest studies is inconsistent with the kindling hypothesis. We then integrate this existing body of research with two emerging biopsychosocial models of BD: the Behavioral Approach System dysregulation model, and the circadian and social rhythm theory. Finally, we present therapeutic implications and suggestions for future research.

Adverse life event reporting and worst illness episodes in unipolar and bipolar affective disorders: measuring environmental risk for genetic research

BACKGROUND

Studies exploring gene-environment interplay in affective disorders now include very large numbers of participants. Methods for evaluating the role of adversity in such studies need to be developed that do not rely on lengthy and labour-intensive interviews. In the present study, a brief questionnaire method for measuring 11 adverse events reported before interview and before their worst illness episodes by bipolar, unipolar and healthy control participants, participating in genetic association studies, was evaluated.

METHOD

Five hundred and twelve bipolar disorder (BD) participants, 1447 participants with recurrent unipolar depression (UPD) and 1346 psychiatrically healthy control participants underwent the researcher-administered version of the List of Threatening Experiences Questionnaire (LTE-Q) for the 6 months before their worst affective episodes for UPD and BD participants, and for the 6 months before interview for the UPD participants and controls.

RESULTS

UPD and BD cases were significantly more likely to report at least one event, as well as more events in the 6 months before interview and before their worst illness episodes, than healthy controls. Both manic and depressive episodes were significantly associated with adverse events in the BD cases. Depressed mood at the time of interview influenced event reporting in UPD and control participants but not the BD cases. Age was negatively correlated with the number of events reported by controls.

CONCLUSIONS

The researcher-administered LTE-Q provides a measure of case-control differences for adversity that is applicable in large genetic association studies. Confounding factors for event reporting include present mood and age.

A prospective study of stress autonomy versus stress sensitization in adolescents at varied risk for depression

This longitudinal study investigated the stress autonomy, stress sensitization, and depression vulnerability hypotheses in adolescents across 6 years (i.e., Grades 6 through 12). Participants were 240 children (Time 1 mean age = 11.86, SD = 0.57) who varied in risk for depression on the basis of their mother's history of mood disorders. All analyses were conducted as multilevel models to account for nesting in the data. Results were consistent with the stress sensitization hypothesis. The within-subject relation of stress levels to depressive symptoms strengthened with increasing numbers of prior depressive episodes. In addition, evidence consistent with the vulnerability hypothesis was found. The relation of stress levels to depressive symptoms was stronger for adolescents who were at risk for depression on the basis of maternal depression history and for those who had experienced more depressive episodes through Grade 12. These findings suggest that onsets of depression in adolescents may be predicted by both relatively stable and dynamic transactions between stressful life events and vulnerabilities such as maternal depression and youths' own history of depressive episodes.

Genome-wide association study of recurrent major depressive disorder in two European case-control cohorts

Major depressive disorder (MDD) is a highly prevalent disorder with substantial heritability. Heritability has been shown to be substantial and higher in the variant of MDD characterized by recurrent episodes of depression. Genetic studies have thus far failed to identify clear and consistent evidence of genetic risk factors for MDD. We conducted a genome-wide association study (GWAS) in two independent datasets. The first GWAS was performed on 1022 recurrent MDD patients and 1000 controls genotyped on the Illumina 550 platform. The second was conducted on 492 recurrent MDD patients and 1052 controls selected from a population-based collection, genotyped on the Affymetrix 5.0 platform. Neither GWAS identified any SNP that achieved GWAS significance. We obtained imputed genotypes at the Illumina loci for the individuals genotyped on the Affymetrix platform, and performed a meta-analysis of the two GWASs for this common set of approximately half a million SNPs. The meta-analysis did not yield genome-wide significant results either. The results from our study suggest that SNPs with substantial odds ratio are unlikely to exist for MDD, at least in our datasets and among the relatively common SNPs genotyped or tagged by the half-million-loci arrays. Meta-analysis of larger datasets is warranted to identify SNPs with smaller effects or with rarer allele frequencies that contribute to the risk of MDD.

The genetics of affective disorder and suicide

Suicidal behaviour shows evidence of familial clustering and the twin data on completed suicide suggest moderate heritability. The extent to which the genetics of suicidal behaviour overlaps with the genetics of affective disorders is unclear but there is overwhelming evidence that both bipolar and unipolar disorder are substantially influenced by genes. So far, candidate gene studies of suicidality have provoked much interest, but recently, attention has also turned to candidate gene approaches to suicidal ideation emerging during antidepressant treatment. The advent of genome-wide association studies (GWAS) has had a major impact on studies of affective disorder with some provocative new findings. The GWAS approach is also beginning to be applied in the search for genes that underlie suicidal ideation and behaviour.

Environmental exposures and their genetic or environmental contribution to depression and fatigue: a twin study in Sri Lanka

BACKGROUND

There is very little genetically informative research identifying true environmental risks for psychiatric conditions. These may be best explored in regions with diverse environmental exposures. The current study aimed to explore similarities and differences in such risks contributing to depression and fatigue.

METHODS

Home interviews assessed depression (lifetime-ever), fatigue and environmental exposures in 4,024 randomly selected twins from a population-based register in the Colombo district of Sri Lanka.

RESULTS

Early school leaving and standard of living showed environmentally-mediated effects on depression, in men. In women, life events were associated with depression partly through genetic pathways (however, the temporal order is consistent with life events being an outcome of depression, as well as the other way around). For fatigue, there were environmentally mediated effects (through early school leaving and life events) and strong suggestions of family-environmental influences.

CONCLUSIONS

Compared to previous studies from higher-income countries, novel environmentally-mediated risk factors for depression and fatigue were identified in Sri Lanka. But as seen elsewhere, the association between life events and depression was partially genetically mediated in women. These results have implications for understanding environmental mechanisms around the world.

Life events, anxious depression and personality: a prospective and genetic study

BACKGROUND

The association between life events and anxious depression might be due to causality or to gene-environment correlation. We examined unidirectional and reciprocal causality and a gene-environment correlation model, in which genes that influence the vulnerability for anxious depression also increase the risk of exposure to life events. The effect of genes that influence environmental exposure might be mediated through personality and we therefore also examined the association between life events and personality (neuroticism and extraversion).

METHOD

Information on life events, anxious depression, neuroticism and extraversion was collected in 5782 monozygotic (MZ) and dizygotic (DZ) twins who participated in a longitudinal survey study of the Netherlands Twin Register. To examine causality, data were analysed longitudinally. To examine gene-environment correlation, the co-twin control method was used.

RESULTS

Anxious depression and, to a lesser extent, neuroticism scores increased after exposure to life events. Anxious depression and neuroticism also predicted the experience of life events. Prospectively, extraversion was not associated with life events. Anxious depression, neuroticism and extraversion scores did not differ between the non-exposed subjects of MZ and DZ twin pairs and unrelated subjects discordant for life events.

CONCLUSIONS

Our findings suggest that reciprocal causation explains the relationship between life events and anxious depression and between life events and neuroticism. Extraversion is not related to life events. No evidence was found for gene-environment correlation, i.e. the genes that influence anxious depression, neuroticism or extraversion do not overlap with the genes that increase the risk of exposure to life events.

[The genetics of depressive disorders]

Among the most common severe psychiatric disorders worldwide, depressive disorders are a leading cause of morbidity, the onset usually occurring during childhood or adolescence. Symptomatology, prevalence, outcome and treatment differentiate depressive disorder nosologically as being either unipolar depression or bipolar disorder, which is characterized by one or more episodes of mania with or without episodes of depression. Genetic factors decisively influence the susceptibility to depressive disorders. Family studies and twin studies have been essential in defining the magnitude of familial risk and liability to heritability, particularly in the case of bipolar disorder. In recent years, linkage and association studies have made great strides towards identifying candidate genes. Particularly the s-allele of the serotonin transporter has been repeatedly confirmed to be a risk factor. Meta-analyses suggest, however, that the genetic contributions of the ascertained loci are relatively small. Along with genetic factors, environmental factors are heavily involved. Gene-environment action plays a pivotal role, particularly in unipolar depression. The genetic disposition seems to be modulated by a protective or pathogenic environment. Early-onset disorders must be further investigated in future as studies to date are somewhat limited.

Attributional style and depression

BACKGROUND

Few studies have examined whether attributional style (an individual's explanation of why events happen) is a genetically influenced vulnerability factor for depression.

AIMS

To investigate whether attributional style is an enduring vulnerability trait for recurrent depression.

METHOD

As part of the Cardiff Depression Study, we interviewed 108 people with depression and their siblings, and a control group of 105 healthy individuals and their siblings, using the Schedules for Clinical Assessment in Neuropsychiatry and the Life Events and Difficulties Schedule. Participants also completed the Attributional Style Questionnaire.

RESULTS

Regression analyses showed that attributional style results from mood state and is not a familial risk factor for depression. However, the tendency to internalise negative events was related to having had a prior episode of depression, suggesting a ;scarring' effect. Also, non-severe events were associated with one subset of optimistic attributions.

CONCLUSIONS

Attributional style mainly measures current mood and does not reflect a familial risk factor for depression.

The interplay of familial depression liability and adverse events in predicting the first onset of depression during a 10-year follow-up

BACKGROUND

The aim of the present article is to explore interaction and correlation effects between familial depression liability and selected adverse (separation and traumatic) events in predicting the first onset of a major depressive episode (MDE) in a 10-year prospective longitudinal community survey.

METHODS

Analyses are based on 1982 subjects (14 to 24 years at baseline) without baseline MDE who participated during the whole study period and for whom diagnostic information about psychopathology in both parents was available. The offspring's familial depression liability was determined by aggregating information on parental depressive symptoms obtained from family history data and direct interviews with parents. Data were assessed with the Munich-Composite International Diagnostic Interview according to its DSM-IV algorithms.

RESULTS

Adverse events predicted a substantially increased incidence of MDE among respondents with familial liability but not in those without familial liability. There was a significant interaction between familial liability and traumatic events with the strongest effect for the number of severe traumatic events (risk difference = 11.3%; 95% confidence interval = 3.55-19.15). Associations with familial liability were most pronounced for separation events.

CONCLUSIONS

Adverse events are particularly pathogenic in individuals with familial liability. The involvement of interactions and correlations between familial liability and adversity might depend on type, severity, and number of events. Both processes are suggested to be concomitant rather than exclusive.

Familial risk for depression and p3b component as a possible neurocognitive vulnerability marker

OBJECTIVE

Complex genetic mechanisms are involved in the vulnerability to depressive disorders and cognitive dysfunctions found in depression. This study was performed to explore the effect of the familial risk for depression on electrophysiological correlates of attentional functions as demonstrated by an event-related potential (ERP) go/no-go experiment.

METHODS

The component P3b as an indicator of target detection processing was investigated in two groups of healthy subjects with or without a family history of depression (n = 14 each). An electrophysiological source localization method (LORETA) was employed to allow a neuro-anatomical interpretation for the ERP data.

RESULTS

The group with a familial risk for depression showed a reduced P3b amplitude over left temporal areas in contrast to the control group. This two-dimensional effect was associated with a significantly reduced activation of the left middle temporal gyrus.

CONCLUSIONS

The P3b amplitude decrement might represent a neurocognitive vulnerability marker for the development of depression.

The risk for depression conferred by stressful life events is modified by variation at the serotonin transporter 5HTTLPR genotype: evidence from the Spanish PREDICT-Gene cohort

We report results from the PREDICT-Gene case-control study nested in a prospective cohort designed to identify predictors of the onset of depression among adult primary-care attendees. We tested the potential gene-by-environment interaction between 5HTTLPR genotype at the serotonin transporter gene and previous exposure to threatening life events (TLEs) in depression. A total of 737 consecutively recruited participants were genotyped. Additional information was gathered on exposure to TLEs over a 6-month period, socio-demographic data and family history of psychological problems among first-degree relatives. Diagnoses of depression were ascertained using the Composite International Diagnostic Interview (CIDI) by trained interviewers. Two different depressive outcomes were used (ICD-10 depressive episode and ICD-10 severe depressive episode). Both the s/s genotype and exposure to increasing number of TLEs were significantly associated with depression. Moreover, the 5HTTLPR s/s genotype significantly modified the risk conferred by TLEs for both depressive outcomes. Thus, s/s homozygous participants required minimal exposure to TLE (1 TLE) to acquire a level of risk for depression that was only found among l/s or l/l individuals after significantly higher exposure to TLEs (two or more TLEs). The interaction was more apparent when applied to the diagnosis of ICD-10 severe depressive episode and after adjusting for gender, age and family history of psychological problems. Likelihood ratios tests for the interaction were statistically significant for both depressive outcomes (ICD-10 depressive episode: LR X(2)=4.7, P=0.09 (crude), LR-X(2)=6.4, P=0.04 (adjusted); ICD-10 severe depressive episode: LR X(2)=6.9, P=0.032 (crude), LR-X(2)=8.1, P=0.017 (adjusted)).

Implications of high-risk family studies for prevention of depression

The high-risk family study is a powerful design that facilitates identification of early forms of expression of depression and premorbid vulnerability, risk, and protective factors that are important for defining prevention targets and program foci. This paper (1) highlights the strengths of high-risk studies for informing early intervention efforts; (2) summarizes findings of familial aggregation from controlled high-risk studies of depression; and (3) briefly reviews evidence for potential mediators (i.e., early forms of expression, vulnerability factors) that explain familial risk and for moderators (i.e., interactive risk and protective factors) that enhance or minimize familial risk. New data from the Yale High-Risk Study of Comorbidity of Substance Use and Affective Disorders are presented to exemplify strategies for identifying specific familial pathways to depression among offspring of parents with substance and anxiety disorders. Likewise, parental depression is associated with a range of emotional and behavioral problems, including anxiety and conduct disorder, in their offspring. These nonspecific effects, together with emerging findings on mechanisms of risk, support early intervention efforts that target a range of youth at risk for depression through multipronged approaches that attend to the individual characteristics of the child and parent, clinical comorbidity, and the broader family and social context.

Gene-environment interplay and psychopathology: multiple varieties but real effects

Gene-environment interplay is a general term that covers several divergent concepts with different meanings and different implications. In this review, we evaluate research evidence on four varieties of gene-environment interplay. First, we consider epigenetic mechanisms by which environmental influences alter the effects of genes. Second, we focus on variations in heritability according to environmental circumstances. Third, we discuss what is known about gene-environment correlations. Finally, we assess concepts and findings on the interaction between specific identified genes and specific measured environmental risks. In order to provide an understanding of what may be involved in gene-environment interplay, we begin our presentation with a brief historical review of prevailing views about the role of genetic and environmental factors in the causation of mental disorders, and we provide a simplified account of some of the key features of how genes 'work'.

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.

Life stress, the "kindling" hypothesis, and the recurrence of depression: considerations from a life stress perspective

Major depression is frequently characterized by recurrent episodes over the life course. First lifetime episodes of depression, however, are typically more strongly associated with major life stress than are successive recurrences. A key theoretical issue involves how the role of major life stress changes from an initial episode over subsequent recurrences. The primary conceptual framework for research on life stress and recurrence of depression is the "kindling" hypothesis (R. M. Post, 1992). Despite the strengths of the kindling hypothesis, a review of the research literature reveals inconsistencies and confusion about life stress and its implications for the recurrence of depression. Adopting a life stress perspective, the authors introduce 3 major themes that resolve the inconsistencies in the current literature. They integrate these themes and extrapolate the ideas with available data to develop a preliminary framework for evaluating competing explanatory models and to guide research on life stress and the recurrence of depression.

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.

Neuroticism: a non-informative marker of vulnerability to psychopathology

BACKGROUND

Neuroticism measures are very popular in psychopathological research, but it is unclear how useful neuroticism is in studies of the aetiology of psychopathology.

METHOD

A conceptual examination was made of the literature on the association of neuroticism and psychopathology, the ontological status of neuroticism, the purport of neuroticism questionnaires, and causal issues.

RESULTS

The research on which neuroticism is built has historically been based solely on the factor analyses of the common adjectives used to describe usual behaviours. An abundance of studies have shown that neuroticism scores predict life stress, psychological distress, emotional disorders, psychotic symptoms, substance abuse, physical tension-related symptoms, medically unexplained physical symptoms, and health care utilisation. This evidence suggests that neuroticism scales index vulnerability to many forms of negative affect and psychiatric disorder. However, the associations do not clarify the nature of this vulnerability nor the underlying psychobiological mechanisms. We present evidence that neuroticism scores reflect a person's characteristic (or mean) level of distress over a protracted period of time. In this perspective, even prospective associations of neuroticism with mental health outcomes are basically futile, and largely tautological since scores on any characteristic with substantial within-subject stability will predict, by definition, that characteristic and related variables at later points in time.

CONCLUSION

Neuroticism is not an explanatory concept in the aetiology of psychopathology, since it measures a person's characteristic level of distress over a protracted period of time. This situation will not change until knowledge becomes available about: (i) the mechanisms that produce high neuroticism scores (and, therefore, also psychopathology) and (ii) its neurobiological substrate. Only then will we understand why neuroticism appears to "predict" the outcomes it predicts.

Stressful life events and affective illness

OBJECTIVE

To investigate the association between the occurrence of affective illnesses and the number/type of experienced negative stressful life events in a twin material. A case-control study with an unrelated twin as control to the case and a co-twin control study were both undertaken with the same material.

METHOD

Postal questionnaire responses were used for confirming diagnosis and to inventory stressful life events. Risk ratios (RR) for groups of events were calculated using conditional logistic regression.

RESULTS

A dose-response relationship was observed for the association between stressful life events and affective illness. The RRs for specific groups of exposures were higher in the co-twin control study and higher for dizygotic twin pairs than for monozygotic twin pairs.

CONCLUSION

Individuals with a history of affective illness select themselves into high-risk environments, in part due to their genetic propensity to the disease. Thus, the association represents a classic genotype-environment correlation.

Facial pain, depression and stress - connections and directions

Chronic facial pain is associated with depression, stress and other chronic pain disorders such as fibromyalgia. There is growing evidence that all these conditions share underlying pathophysiological processes. This review explores this relationship and examines the role of the main stress hormone axis, the hypothalamic-pituitary-adrenal axis, in the pathogenesis of facial pain including possible future therapeutic approaches.

Life events and changes in the course of depression in young adults

BACKGROUND

Few community-based studies have examined the impact of life events, life conditions and life changes on the course of depression. This paper examines associations of life events on depressive symptom onset, improvement, and stability.

METHODS

Direct interview data from the Early Developmental Stages of Psychopathology Study (EDSP), a 4-5 year prospective-longitudinal design based on a representative community sample of adolescents and young adults, aged 14-24 years at baseline, are used. Life events were measured using the Munich Event-Questionnaire (MEL) consisting of 83 explicit items from various social role areas and subscales for the assessment of life event clusters categorized according to dimensions such as positive and negative and controllable and uncontrollable. Depressive disorders were assessed with the DSM-IV version of the Munich Composite Diagnostic Interview (M-CIDI). Multiple logistic regression analyses examined the effects of 22 predictors on the course of depression (onset, improvement, stability).

RESULTS

Younger age, low social class, negative and stressful life events linked to the family were associated with increased risk of new onset of depression. Anxiety was a significant independent predictor of new onset of depression. Absence of stressful school and family events was related to improvement in depression. The weighted total number of life events predicted stable depression.

CONCLUSIONS

The association between life events and the course of depression appears to vary according to the outcome being examined, with different clusters of life events differentially predicting onset, improvement, and stability.