Is low mood an adaptation? Evidence for subtypes with symptoms that match precipitants

Building an Early Warning System for Depression: Rationale, Objectives, and Methods of the WARN-D Study

Background

Depression is common, debilitating, often chronic, and affects young people disproportionately. Given that only 50% of patients improve under initial treatment, experts agree that prevention is the most effective way to change depression's global disease burden. The biggest barrier to successful prevention is to identify individuals at risk for depression in the near future. To close this gap, this protocol paper introduces the WARN-D study, our effort to build a personalized early warning system for depression.

Method

To develop the system, we follow around 2,000 students over 2 years. Stage 1 comprises an extensive baseline assessment in which we collect a broad set of predictors for depression. Stage 2 lasts 3 months and zooms into participants' daily experiences that may predict depression; we use smartwatches to collect digital phenotype data such as sleep and activity, and we use a smartphone app to query participants about their experiences 4 times a day and once every Sunday. In Stage 3, we follow participants for 21 months, assessing transdiagnostic outcomes (including stress, functional impairment, anxiety, and depression) as well as additional predictors for future depression every 3 months. Collected data will be utilized to build a personalized prediction model for depression onset.

Discussion

Overall, WARN-D will function similarly to a weather forecast, with the core difference that one can only seek shelter from a thunderstorm and clean up afterwards, while depression may be successfully prevented before it occurs.

Interrelationships between childhood maltreatment, depressive symptoms, functional impairment, and quality of life in patients with major depressive disorder: A network analysis approach

BACKGROUND

Childhood maltreatment continues to pose a great challenge to psychiatry. Although there is growing evidence demonstrating that childhood maltreatment is an important risk factor for depressive disorders, it remains to be elucidated which specific symptoms occur after exposure to different kinds of childhood maltreatment, and whether certain pathways may account for these associations.

PARTICIPANTS AND SETTINGS

A total of 203 adult patients (18-53 years old) with MDD, diagnosed by Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) criteria, were recruited from the outpatient clinic of Beijing Anding Hospital, Capital Medical University.

METHODS

Childhood maltreatment, depressive symptoms, functional impairment, and quality of life were evaluated by the Childhood Trauma Questionnaire - Short Form (CTQ-SF), 17-item Hamilton Depression Rating Scale (HAMD-17), Sheehan Disability Scale (SDS), and Quality of Life Enjoyment and Satisfaction Questionnaire-Short Form (Q-LES-Q-SF). Undirected network analysis was used to explore the most relevant connections between them. Bayesian network analysis was used to estimate a directed acyclic graph (DAG) while investigating the most likely direction of the putative causal association.

RESULTS

In network analysis, the strongest edges were a positive correlation between emotional abuse and suicidal behavior as well as a negative association between emotional neglect and age of onset. In DAG analysis, emotional abuse emerged as the most pivotal network node, triggering both suicidal behaviors and depression symptoms.

CONCLUSIONS

Emotional abuse appears to be an extremely harmful form of childhood maltreatment in the clinical presentation of depression. This study has promise in informing the clinical intervention of depression.

An evolutionary investigation of depressed mood: The relationship between daily stressors and patterns of depressive symptoms

BACKGROUND AND OBJECTIVES

The situation-symptom congruence hypothesis (SSCH; (Keller & Nesse, 2006), grounded in evolutionary theory, argues that different types of adversity should lead to distinct patterns of depressive symptoms that help individuals deal with adaptive challenges. Situation-symptom congruence hypotheses were tested in this study using experience sampling methodology.

METHODS

Two hundred and sixty-five individuals, including 54% who scored at least 16 on the Center for Epidemiologic Studies Revised Depression Scale, responded to text prompts daily for up to 9 days, reporting depressive symptoms as well as the most stressful event or issue they had experienced or focused on within the past 24 h.

RESULTS

Multilevel modeling analyses indicated that the relationships between stressors and depressive symptom patterns were largely consistent with SSCH predictions. All stressors were significantly associated with symptoms hypothesized to be adaptive in response to those stressors. Moreover, in separate analyses, nine of the ten symptoms examined were either predicted by the stressors hypothesized to lead to that symptom or negatively related to stressors hypothesized to not elicit those symptoms.

LIMITATIONS

It is unclear whether the results generalize to those diagnosed with a major depressive disorder; the study did not assess actual life events.

CONCLUSIONS

Findings suggest that depressive symptoms may, in part, be adaptations that have evolved through natural selection to help individuals cope with adverse situations.

Revisiting the theoretical and methodological foundations of depression measurement

Depressive disorders are among the leading causes of global disease burden, but there has been limited progress in understanding the causes and treatments for these disorders. In this Perspective, we suggest that such progress crucially depends on our ability to measure depression. We review the many problems with depression measurement, including limited evidence of validity and reliability. These issues raise grave concerns about common uses of depression measures, such as diagnosis or tracking treatment progress. We argue that shortcomings arise because depression measurement rests on shaky methodological and theoretical foundations. Moving forward, we need to break with the field's tradition that has, for decades, divorced theories about depression from how we measure it. Instead, we suggest that epistemic iteration, an iterative exchange between theory and measurement, provides a crucial avenue for depression measurement to progress.

Strength is negatively associated with depression and accounts for some of the sex difference

Background

Depression occurs about twice as often in women as in men, a disparity that remains poorly understood. In a previous publication, Hagen and Rosenström predicted and found that grip strength, a highly sexually dimorphic index of physical formidability, mediated much of the effect of sex on depression. Striking results like this are more likely to be published than null results, potentially biasing the scientific record. It is therefore critical to replicate and extend them.

Methodology

Using new data from the 2013–14 cycle of the National Health and Nutrition Examination Survey, a nationally representative sample of US households (n = 3650), we replicated models of the effect of sex and grip strength on depression reported in Hagen and Rosenström, along with additional potential confounds and a new detailed symptom-level exploration.

Results

Overall, the effects from the original paper were reproduced although with smaller effect sizes. Grip strength mediated 38% of the effect of sex on depression, compared to 63% in Hagen and Rosenström. These results were extended with findings that grip strength had a stronger association with some depression symptoms, like suicidality, low interest and low mood than with other symptoms, like appetite changes.

Conclusions

Grip strength is negatively associated with depression, especially its cognitive–affective symptoms, controlling for numerous possible confounds. Although many factors influence depression, few of these reliably occur cross-culturally in a sex-stratified manner and so are unlikely to explain the well-established, cross-cultural sex difference in depression. The sex difference in upper body strength occurs in all populations and is therefore a candidate evolutionary explanation for some of the sex difference in depression.

Lay summary: Why are women at twice the risk of developing depression as men? Depression typically occurs during social conflicts, such as physical or sexual abuse. Physically strong individuals can often single-handedly resolve conflicts in their favor, whereas physically weaker individuals often need help from others. We argue that depression is a credible cry for help. Because men generally have greater strength than women, we argue that men may be more likely to resolve conflicts using physical formidability and women to signal others for help. We find that higher grip strength is associated with lower depression, particularly symptoms like feeling down or thoughts of suicide and that strength accounts for part of the sex difference in rates of depression.

Prevalence and factors related to psychological distress among ethnic minority adults in a semi-modern village in rural Vietnam: an evolutionary mismatch framework

Background and objectives

Psychological distress is one of the greatest health threats facing humanity and has been hypothesized to represent an evolutionary mismatch. This hypothesis can be tested in semi-traditional societies that are undergoing transitions to modern lifestyles. This study used an evolutionary medicine framework to examine the predictors of psychological distress symptomology in a semi-modern ethnic minority village in rural Vietnam that is transitioning into a developing economy.

Methodology

A cross-sectional survey was conducted in Chieng Sai Village among White Thai ethnic minority adults aged 18-75. The DASS-21 scale was used to measure the prevalence of psychological distress symptoms (depression and stress), and a closed format questionnaire was used to collect data on independent variables within an evolutionary mismatch framework. Binary logistic regression analyses were used to determine associated factors of psychological distress symptomology.

Results

The prevalence of psychological distress symptoms was 22% (depression = 16.9%, stress = 16.3%). Common features of modernity, such as low levels of exercise, boredom, and low income, showed positive associations with psychological distress, while lifestyle features that were more similar to those expected in the evolutionary past and that fulfill evolutionary adaptations, such as getting enough sleep, adequate physical exertion, and access to resources (earning a sufficient income), showed negative associations with psychological distress.

Conclusions and implications

This study suggests that modern lifestyles might have generated evolutionary mismatches that are negatively impacting mental health in Chieng Sai Village. Further investigations on mental health in rural Vietnam are warrented. Future research should focus on determining the causal relationship between psychological distress and evolutionary mismatches. Evolutionary medicine approaches to understanding and preventing psychological distress are potential forces of insight to be considered in public health and educational policy.

Lay summary

Approximately 22% of White Thai ethnic minority adults in the village of Cheing Sai reported psychological distress symptoms. I found that lifestyle factors prevalent in modern society had positive associations with psychological distress symptomology, while lifestyle factors that mimic aspects of the human evolutionary past, such as adequate physical exertion, had negative associations with psychological distress symptoms.

Romantic Love and Sleep Variations: Potential Proximate Mechanisms and Evolutionary Functions

This article provides a narrative review of what is known about romantic love and sleep variations and provides possible explanations for the association. Romantic love and sleep are described using a comprehensive, unifying framework advocated by Tinbergen. We summarise the findings of studies investigating the relationship between romantic love and sleep. Sleep variations are associated with romantic love in adolescents and young adults. We then detail some proximate mechanisms that may contribute to sleep variations in people experiencing romantic love before considering potential evolutionary functions of sleep variations in people experiencing romantic love. The relationship between symptoms of psychopathology and sleep variations in people experiencing romantic love is described. With the current state of knowledge, it is not possible to determine whether sleep variations associated with romantic love are adaptations or by-products of romantic love. We conclude by proposing areas for future research.

Romantic Relationship Dissolution, Microbiota, and Fibers

Microbiota inhabit nearly every part of our body with the gut microbiota representing the greatest density and absolute abundance. The gut-microbiota-brain axis facilitates bidirectional communication between gut microbiota and the brain. For instance, romantic relationship not only brings joy, it is also associated with increased gut microbiota diversity and health benefits whereas reduced microbiota diversity is related to obesity, cardiac disease, type 2 diabetes, and inflammatory disorders. Research has shown that dietary fibers may increase microbiota diversity and exert antidepressant effect. Among a plethora of life stressors, romantic relationship dissolution is a relatively common and painful experience that people encounter from time to time. Depressed mood, social isolation and poor intake are all associated with romantic relationship dissolution. In this article, it is hypothesized that romantic relationship dissolution is accompanied by decreased gut microbiota diversity which could be corrected with the ingestion of dietary fibers with an additional antidepressant benefit.

Psychological mechanisms and functions of 5-HT and SSRIs in potential therapeutic change: Lessons from the serotonergic modulation of action selection, learning, affect, and social cognition

Uncertainty regarding which psychological mechanisms are fundamental in mediating SSRI treatment outcomes and wide-ranging variability in their efficacy has raised more questions than it has solved. Since subjective mood states are an abstract scientific construct, only available through self-report in humans, and likely involving input from multiple top-down and bottom-up signals, it has been difficult to model at what level SSRIs interact with this process. Converging translational evidence indicates a role for serotonin in modulating context-dependent parameters of action selection, affect, and social cognition; and concurrently supporting learning mechanisms, which promote adaptability and behavioural flexibility. We examine the theoretical basis, ecological validity, and interaction of these constructs and how they may or may not exert a clinical benefit. Specifically, we bridge crucial gaps between disparate lines of research, particularly findings from animal models and human clinical trials, which often seem to present irreconcilable differences. In determining how SSRIs exert their effects, our approach examines the endogenous functions of 5-HT neurons, how 5-HT manipulations affect behaviour in different contexts, and how their therapeutic effects may be exerted in humans - which may illuminate issues of translational models, hierarchical mechanisms, idiographic variables, and social cognition.

Antianhedonic and Antidepressant Effects of Affron®, a Standardized Saffron (Crocus Sativus L.) Extract

Anxiety and depression have high prevalence in the general population, affecting millions of people worldwide, but there is still a need for effective and safe treatments. Nutritional supplements have recently received a lot of attention, particularly saffron. Thus, several pre-clinical studies support a beneficial role for bioactive compounds, such as saffron, in anxiety and depression. Here we used an animal model of depression based on social isolation to assess the effects of affron^®, a standardized saffron extract containing ≥3.5% of total bioactive compounds safranal and crocin isomers. Affron^® was administered both through the oral and the intraperitoneal routes, and several tasks related to anxiety and depression, such as the elevated plus maze, the forced swimming test or the sucrose preference test, were assessed. These tasks model key features of depressive states and anxious states relating to fear, behavioral despair or anhedonia, the lack of motivation and/or pleasure from everyday activities, respectively. Animals receiving oral affron^® displayed behaviors congruent with improvements in their anxious/depressive state, showing the enhanced consumption of a sweet solution, as well as an increase in certain escape responses in the forced swimming test. Our data support a beneficial role for oral saffron in anxious/depressive states.

Personality and boredom at work: the mediating role of job crafting

Purpose

Boredom at work is associated with negative consequences, therefore it is important to investigate whether employees engage in job crafting behaviors that reduce boredom and what are the individual differences associated with these behaviors. The paper aims to discuss these issues.

Design/methodology/approach

A questionnaire study was designed to examine the mediating role of job crafting in the relationship between conscientiousness and emotional stability and boredom among 252 employees (Study 1) and in the relationship between Machiavellianism and psychopathy and boredom among 216 employees (Study 2).

Findings

The results showed that conscientiousness is negatively related to work-related boredom. This relationship is mediated by job crafting. Neuroticism and psychopathy are positively associated with boredom at work, but these relationships are not mediated by job crafting behaviors.

Research limitations/implications

The study was based on self-reported measures, which might raise questions of common-method bias, and the research samples contained mostly women and young employees, which raises questions about generalizability of our findings. At the same time, the cross-sectional design does not allow causal inferences.

Practical implications

Organizations can select employees based on their personality for jobs that predispose to boredom and give them enough autonomy to be able to craft them. Moreover, they can identify employees who need support to manage their boredom and include them in job crafting interventions.

Originality/value

Traditionally, boredom at work has been considered as resulting from characteristics of tasks and jobs. The findings indicate that some employees can make self-initiated changes to their work in order to reduce their boredom and possibly its negative consequences.

How affect shapes status: distinct emotional experiences and expressions facilitate social hierarchy navigation

All human societies are organized hierarchically, and individuals who occupy positions of high social rank typically acquire fitness advantages over lower ranking group members. Here, we argue that certain emotions function, at least in part, to help individuals successfully navigate these hierarchies. We review evidence suggesting that nine distinct emotions - pride, shame, anger, fear, sadness, disgust, contempt, envy, and admiration - influence social rank outcomes in important ways; most notably subjective experiences of these emotions motivate adaptive status-relevant behavior, and nonverbal expressions associated with these emotions send adaptive messages to others which facilitate expressers' attainment and maintenance of social rank. In sum, the reviewed emotions are thought to have intrapersonal and interpersonal consequences relevant to the navigation of social hierarchies.

Predicting loneliness with polygenic scores of social, psychological and psychiatric traits

Loneliness is a heritable trait that accompanies multiple disorders. The association between loneliness and mental health indices may partly be due to inherited biological factors. We constructed polygenic scores for 27 traits related to behavior, cognition and mental health and tested their prediction for self-reported loneliness in a population-based sample of 8798 Dutch individuals. Polygenic scores for major depressive disorder (MDD), schizophrenia and bipolar disorder were significantly associated with loneliness. Of the Big Five personality dimensions, polygenic scores for neuroticism and conscientiousness also significantly predicted loneliness, as did the polygenic scores for subjective well-being, tiredness and self-rated health. When including all polygenic scores simultaneously into one model, only 2 major depression polygenic scores remained as significant predictors of loneliness. When controlling only for these 2 MDD polygenic scores, only neuroticism and schizophrenia remain significant. The total variation explained by all polygenic scores collectively was 1.7%. The association between the propensity to feel lonely and the susceptibility to psychiatric disorders thus pointed to a shared genetic etiology. The predictive power of polygenic scores will increase as the power of the genome-wide association studies on which they are based increases and may lead to clinically useful polygenic scores that can inform on the genetic predisposition to loneliness and mental health.

Depression subtyping based on evolutionary psychiatry: Proximate mechanisms and ultimate functions

Major depressive disorder constitutes one of the leading causes of disability worldwide. However, it is not a unitary disease-it is a heterogeneous syndrome, with patients differing remarkably in symptom profile, pathophysiology and treatment responsiveness. Previous attempts to subtype major depressive disorder have showed limited clinical applicability. We present a classification of major depressive disorder episodes based on the proximate mechanisms that led to the original mood change that caused the depressive episode. We identify discrete depression subtypes that are induced by: 1) infection, 2) long-term stress, 3) loneliness, 4) traumatic experience, 5) hierarchy conflict, 6) grief, 7) romantic rejection, 8) postpartum events, 9) the season, 10) chemicals, 11) somatic diseases and 12) starvation. We further examine the ultimate functions of these subtypes and show that not all types of mood changes that trigger depression are adaptive. Instead, some are clearly maladaptive and some are byproducts of other adaptations. In modern societies, low mood after adverse life events may turn into a pathological depressive state. Modern lifestyle increases susceptibility to inflammatory dysregulation and chronic stress, both of which increase the amount of proinflammatory cytokines in peripheral blood, leading to low mood and sickness behaviour. Proinflammatory cytokines may aggravate the previously adaptive short-term mood changes to a chronic maladaptive depressive state by preventing the normalization of mood after adverse life events. Subtyping depression enables an effective and intelligent long-term treatment of patients in each subtype by treating the underlying causes of depression.

Robust symptom networks in recurrent major depression across different levels of genetic and environmental risk

BACKGROUND

Genetic risk and environmental adversity-both important risk factors for major depression (MD)-are thought to differentially impact on depressive symptom types and associations. Does heterogeneity in these risk factors result in different depressive symptom networks in patients with MD?

METHODS

A clinical sample of 5784 Han Chinese women with recurrent MD were interviewed about their depressive symptoms during their lifetime worst episode of MD. The cases were classified into subgroups based on their genetic risk for MD (family history, polygenic risk score, early age at onset) and severe adversity (childhood sexual abuse, stressful life events). Differences in MD symptom network structure were statistically examined for these subgroups using permutation-based network comparison tests.

RESULTS

Although significant differences in symptom endorsement rates were seen in 18.8% of group comparisons, associations between depressive symptoms were similar across the different subgroups of genetic and environmental risk. Network comparison tests showed no significant differences in network strength, structure, or specific edges (P-value > 0.05) and correlations between edges were strong (0.60-0.71).

LIMITATIONS

This study analyzed depressive symptoms retrospectively reported by severely depressed women using novel statistical methods. Future studies are warranted to investigate whether similar findings hold in prospective longitudinal data, less severely depressed patients, and men.

CONCLUSIONS

Similar depressive symptom networks for MD patients with a higher or lower genetic or environmental risk suggest that differences in these etiological influences may produce similar symptom networks downstream for severely depressed women.

Moving Forward: Challenges and Directions for Psychopathological Network Theory and Methodology

Since the introduction of mental disorders as networks of causally interacting symptoms, this novel framework has received considerable attention. The past years have resulted in over 40 scientific publications and numerous conference symposia and workshops. Now is an excellent moment to take stock of the network approach: What are its most fundamental challenges, and what are potential ways forward in addressing them? After a brief conceptual introduction, we first discuss challenges to network theory: (1) What is the validity of the network approach beyond some commonly investigated disorders such as major depression? (2) How do we best define psychopathological networks and their constituent elements? And (3) how can we gain a better understanding of the causal nature and real-life underpinnings of associations among symptoms? Next, after a short technical introduction to network modeling, we discuss challenges to network methodology: (4) heterogeneity of samples studied with network analytic models, and (5) a lurking replicability crisis in this strongly data-driven and exploratory field. Addressing these challenges may propel the network approach from its adolescence into adulthood and promises advances in understanding psychopathology both at the nomothetic and idiographic level.

affron® a novel saffron extract (Crocus sativus L.) improves mood in healthy adults over 4 weeks in a double-blind, parallel, randomized, placebo-controlled clinical trial

BACKGROUND

In recent years phytotherapy has been explored as a source for alternative treatments for mood disorders. One potential candidate is saffron (Crocus sativus L.), whose main bioactive components are crocins and safranal.

OBJECTIVES

The aim of this study was to investigate the efficacy of affron^®, a standardised stigmas extract from Crocus sativus L. for improving mood, stress, anxiety and sleep quality in healthy adults.

METHODS

In this 3 arm study, 128 participants self-reporting low mood but not diagnosed with depression, were given affron^® at 28mg/day, 22mg/day, or a placebo treatment in a randomized, double-blind, placebo-controlled trial for 4 weeks. Mood was measured at baseline and at the end of the study, using the POMS (primary outcome measure) and PANAS questionnaires, and the DASS-21 scale. Sleep was monitored using Sleep Quality Index (PSQI).

RESULTS

Analysis indicated a significant decrease in negative mood and symptoms related to stress and anxiety at a 28mg/day dose (with a significant difference between 28mg/day and placebo on the POMS Total Mood Disturbance scale, p<0.001, d=-1.10), but no treatment effect at the 22mg/day dose.

LIMITATIONS

The main weaknesses of this investigation were found in the self-reporting nature of both the screening and the testing.

CONCLUSIONS

affron^® increased mood, reduced anxiety and managed stress without side effects, offering a natural alternative to standard treatments.

Genetic and environmental influences on the codevelopment among borderline personality disorder traits, major depression symptoms, and substance use disorder symptoms from adolescence to young adulthood

Although borderline personality disorder (BPD) traits decline from adolescence to adulthood, comorbid psychopathology such as symptoms of major depressive disorder (MDD), alcohol use disorder (AUD), and drug use disorders (DUDs) likely disrupt this normative decline. Using a longitudinal sample of female twins (N = 1,763), we examined if levels of BPD traits were correlated with changes in MDD, AUD, and DUD symptoms from ages 14 to 24. A parallel process biometric latent growth model examined the contributions of genetic and environmental factors to the relationships between developmental components of these phenotypes. Higher BPD trait levels predicted a greater rate of increase in AUD and DUD symptoms, and higher AUD and DUD symptoms predicted a slower rate of decline of BPD traits from ages 14 to 24. Common genetic influences accounted for the associations between BPD traits and each disorder, as well as the interrelationships of AUD and DUD symptoms. Both genetic and nonshared environmental influences accounted for the correlated levels between BPD traits and MDD symptoms, but solely environmental influences accounted for the correlated changes between the two over time. Results indicate that higher levels of BPD traits may contribute to an earlier onset and faster escalation of AUD and DUD symptoms, and substance use problems slow the normative decline in BPD traits. Overall, our data suggests that primarily genetic influences contribute to the comorbidity between BPD features and substance use disorder symptoms. We discuss our data in the context of two major theories of developmental psychopathology and comorbidity.

Reconsidering the definition of Major Depression based on Collaborative Psychiatric Epidemiology Surveys

BACKGROUND

Diagnostic definitions for depressive disorders remain a debated topic, despite their central role in clinical practice and research. We use both recent evidence and nationally representative data to derive an empirically-based modification of DSM-IV/-5 Major Depressive Disorder (MDD).

METHOD

A modified MDD diagnosis was derived by analyzing data from Collaborative Psychiatric Epidemiology Surveys, a multistage probability sample of adults (n=20 013; age ≥ 18 years) in coterminous USA, Alaska and Hawaii. The old and the newly suggested MDD definitions were compared for their associated disability (WHO Disability Assessment Schedule and number of disability days in past month), suicide attempt, and other covariates.

RESULTS

Our data-driven definition for major depression was "lack of interest to all or most things" plus four other symptoms from the set {weight gain, weight loss, insomnia, psychomotor retardation, fatigue, feelings of worthlessness, diminished ability to think/concentrate, suicidal ideation/attempt}. The new definition captured all the disability implied by MDD and excluded cases that showed no greater disability than the general population nor increased risk of suicide attempts. The lifetime prevalence of the new diagnosis was 14.7% (95% CI=14-15.4%) of the population, slightly less than for the old definition (16.4%; CI=15.4-17.3%).

LIMITATIONS

Only conservative modifications of MDD could be studied, because of restrictions in the symptom data.

CONCLUSIONS

With only small adjusting, the new definition for major depression may be more clinically relevant than the old one, and could serve as a conservative replacement for the old definition.

The role of ecodevelopmental context and self-concept in depressive and externalizing symptoms in Hispanic adolescents

The present study examined the extent to which self-concept is related to depressive and externalizing symptoms in Hispanic adolescents, in the presence of contextual variables. A sample of 167 Hispanic adolescents and their primary caregivers completed measures of family functioning, and of school bonding and competence. Adolescents completed measures of self-concept and peer antisocial behavior. Reports of depressive symptoms were gathered from adolescents only, whereas reports of externalizing symptoms were gathered from both adolescents and parents. Self-concept was directly and negatively related to adolescent reports of both depressive and externalizing symptoms, but not to parent reports of externalizing problems. The relationships of school bonding and peer antisocial behavior to adolescent-reported adjustment appeared to operate through self-concept, and the strong bivariate relationships of adolescent-reported family functioning to adolescent-reported adjustment appeared to operate through school bonding and self-concept. Implications for further research and for intervention are discussed.

Depression as sickness behavior? A test of the host defense hypothesis in a high pathogen population

Sadness is an emotion universally recognized across cultures, suggesting it plays an important functional role in regulating human behavior. Numerous adaptive explanations of persistent sadness interfering with daily functioning (hereafter "depression") have been proposed, but most do not explain frequent bidirectional associations between depression and greater immune activation. Here we test several predictions of the host defense hypothesis, which posits that depression is part of a broader coordinated evolved response to infection or tissue injury (i.e. "sickness behavior") that promotes energy conservation and reallocation to facilitate immune activation. In a high pathogen population of lean and relatively egalitarian Bolivian forager-horticulturalists, we test whether depression and its symptoms are associated with greater baseline concentration of immune biomarkers reliably associated with depression in Western populations (i.e. tumor necrosis factor alpha [TNF-α], interleukin-1 beta [IL-1β], interleukin-6 [IL-6], and C-reactive protein [CRP]). We also test whether greater pro-inflammatory cytokine responses to ex vivo antigen stimulation are associated with depression and its symptoms, which is expected if depression facilitates immune activation. These predictions are largely supported in a sample of older adult Tsimane (mean±SD age=53.2±11.0, range=34-85, n=649) after adjusting for potential confounders. Emotional, cognitive and somatic symptoms of depression are each associated with greater immune activation, both at baseline and in response to ex vivo stimulation. The association between depression and greater immune activation is therefore not unique to Western populations. While our findings are not predicted by other adaptive hypotheses of depression, they are not incompatible with those hypotheses and future research is necessary to isolate and test competing predictions.

Development of a cognitive bias methodology for measuring low mood in chimpanzees

There is an ethical and scientific need for objective, well-validated measures of low mood in captive chimpanzees. We describe the development of a novel cognitive task designed to measure ‘pessimistic’ bias in judgments of expectation of reward, a cognitive marker of low mood previously validated in a wide range of species, and report training and test data from three common chimpanzees (Pan troglodytes). The chimpanzees were trained on an arbitrary visual discrimination in which lifting a pale grey paper cone was associated with reinforcement with a peanut, whereas lifting a dark grey cone was associated with no reward. The discrimination was trained by sequentially presenting the two cone types until significant differences in latency to touch the cone types emerged, and was confirmed by simultaneously presenting both cone types in choice trials. Subjects were subsequently tested on their latency to touch unrewarded cones of three intermediate shades of grey not previously seen. Pessimism was indicated by the similarity between the latency to touch intermediate cones and the latency to touch the trained, unreinforced, dark grey cones. Three subjects completed training and testing, two adult males and one adult female. All subjects learnt the discrimination (107–240 trials), and retained it during five sessions of testing. There was no evidence that latencies to lift intermediate cones increased over testing, as would have occurred if subjects learnt that these were never rewarded, suggesting that the task could be used for repeated testing of individual animals. There was a significant difference between subjects in their relative latencies to touch intermediate cones (pessimism index) that emerged following the second test session, and was not changed by the addition of further data. The most dominant male subject was least pessimistic, and the female most pessimistic. We argue that the task has the potential to be used to assess longitudinal changes in sub-clinical levels of low mood in chimpanzees, however further work with a larger sample of animals is required to validate this claim.

Depression sum-scores don't add up: why analyzing specific depression symptoms is essential

Most measures of depression severity are based on the number of reported symptoms, and threshold scores are often used to classify individuals as healthy or depressed. This method--and research results based on it--are valid if depression is a single condition, and all symptoms are equally good severity indicators. Here, we review a host of studies documenting that specific depressive symptoms like sad mood, insomnia, concentration problems, and suicidal ideation are distinct phenomena that differ from each other in important dimensions such as underlying biology, impact on impairment, and risk factors. Furthermore, specific life events predict increases in particular depression symptoms, and there is evidence for direct causal links among symptoms. We suggest that the pervasive use of sum-scores to estimate depression severity has obfuscated crucial insights and contributed to the lack of progress in key research areas such as identifying biomarkers and more efficacious antidepressants. The analysis of individual symptoms and their causal associations offers a way forward. We offer specific suggestions with practical implications for future research.

An adaptationist perspective on the etiology of depression

Major depressive disorder (MDD) presents with a variety of symptoms and responds to a wide range of treatment interventions. Diagnostic criteria collapse multiple syndromes with distinct etiologies into the same disorder. MDD is typically understood as a malfunction of neurotransmission or brain circuitry regulating mood, pleasure and reward, or executive function. However, research from an evolutionary perspective suggests that the "normal" functioning of adaptations may also generate symptoms meeting diagnostic criteria. Functioning adaptations may be an underappreciated etiological pathway to MDD. Many adaptive functions for depressive symptoms have been suggested: biasing cognition to avoid losses, conserving energy, disengaging from unobtainable goals, signaling submission, soliciting resources, and promoting analytical thinking. We review the potential role of these adaptive functions and how they can lead to specific clusters of depressive symptoms. Understanding MDD from such a perspective reduces the heterogeneity of cases and may help to select the best intervention for each patient. We discuss the implications of different adaptive and maladaptive etiological pathways for the use of antidepressants and various modes of psychotherapy. In particular, instances of MDD caused by functioning adaptations may benefit most from treatments that support the adaptive function, or that target the precipitating causal stressor. We conclude that an evolutionary approach to the study of MDD may be one of the more promising approaches to reduce its heterogeneity and to better match patients and treatment.

Depression is not a consistent syndrome: An investigation of unique symptom patterns in the STAR*D study

BACKGROUND

The DSM-5 encompasses a wide range of symptoms for Major Depressive Disorder (MDD). Symptoms are commonly added up to sum-scores, and thresholds differentiate between healthy and depressed individuals. The underlying assumption is that all patients diagnosed with MDD have a similar condition, and that sum-scores accurately reflect the severity of this condition. To test this assumption, we examined the number of DSM-5 depression symptom patterns in the "Sequenced Treatment Alternatives to Relieve Depression" (STAR*D) study.

METHODS

We investigated the number of unique symptom profiles reported by 3703 depressed outpatients at the beginning of the first treatment stage of STAR*D.

RESULTS

Overall, we identified 1030 unique symptom profiles. Of these profiles, 864 profiles (83.9%) were endorsed by five or fewer subjects, and 501 profiles (48.6%) were endorsed by only one individual. The most common symptom profile exhibited a frequency of only 1.8%. Controlling for overall depression severity did not reduce the amount of observed heterogeneity.

LIMITATIONS

Symptoms were dichotomized to construct symptom profiles. Many subjects enrolled in STAR*D reported medical conditions for which prescribed medications may have affected symptom presentation.

CONCLUSIONS

The substantial symptom variation among individuals who all qualify for one diagnosis calls into question the status of MDD as a specific consistent syndrome and offers a potential explanation for the difficulty in documenting treatment efficacy. We suggest that the analysis of individual symptoms, their patterns, and their causal associations will provide insights that could not be discovered in studies relying on only sum-scores.

Depression is more than the sum score of its parts: individual DSM symptoms have different risk factors

BACKGROUND

For diagnostic purposes, the nine symptoms that compose the DSM-5 criteria for major depressive disorder (MDD) are assumed to be interchangeable indicators of one underlying disorder, implying that they should all have similar risk factors. The present study investigates this hypothesis, using a population cohort that shifts from low to elevated depression levels.

METHOD

We assessed the nine DSM-5 MDD criterion symptoms (using the Patient Health Questionnaire; PHQ-9) and seven depression risk factors (personal and family MDD history, sex, childhood stress, neuroticism, work hours, and stressful life events) in a longitudinal study of medical interns prior to and throughout internship (n = 1289). We tested whether risk factors varied across symptoms, and whether a latent disease model could account for heterogeneity between symptoms.

RESULTS

All MDD symptoms increased significantly during residency training. Four risk factors predicted increases in unique subsets of PHQ-9 symptoms over time (depression history, childhood stress, sex, and stressful life events), whereas neuroticism and work hours predicted increases in all symptoms, albeit to varying magnitudes. MDD family history did not predict increases in any symptom. The strong heterogeneity of associations persisted after controlling for a latent depression factor.

CONCLUSIONS

The influence of risk factors varies substantially across DSM depression criterion symptoms. As symptoms are etiologically heterogeneous, considering individual symptoms in addition to depression diagnosis might offer important insights obfuscated by symptom sum scores.

First principles of Hamiltonian medicine

We introduce the field of Hamiltonian medicine, which centres on the roles of genetic relatedness in human health and disease. Hamiltonian medicine represents the application of basic social-evolution theory, for interactions involving kinship, to core issues in medicine such as pathogens, cancer, optimal growth and mental illness. It encompasses three domains, which involve conflict and cooperation between: (i) microbes or cancer cells, within humans, (ii) genes expressed in humans, (iii) human individuals. A set of six core principles, based on these domains and their interfaces, serves to conceptually organize the field, and contextualize illustrative examples. The primary usefulness of Hamiltonian medicine is that, like Darwinian medicine more generally, it provides novel insights into what data will be productive to collect, to address important clinical and public health problems. Our synthesis of this nascent field is intended predominantly for evolutionary and behavioural biologists who aspire to address questions directly relevant to human health and disease.

The use of symptom dimensions to investigate the longitudinal effects of life events on depressive and anxiety symptomatology

BACKGROUND

Findings on the association between life events and depression have been quite inconsistent. This could be due to the heterogeneity of traditionally used depression outcomes. The aim of this study was to investigate whether specific symptom dimensions can be used as an alternative to detect more specific life event effects.

METHODS

Participants with/without psychiatric diagnoses were included (n=2252). Dimensions of the tripartite model (General Distress [GD], Anhedonic Depression [AD] and Anxious Arousal [AA]) were assessed at baseline, 1-year and 2-year follow-up. Life events occurring between measurements were assessed retrospectively. Longitudinal associations between life events and dimensional scores were analysed with Linear Mixed Models.

RESULTS

Occurrence of negative life events was associated with increasing GD and AA, and less with AD. Positive life events were associated with decreasing GD and AD, but not with AA. The association between negative life events and AD was larger in the absence of previous psychiatric problems, lending support to a dimension-specific 'kindling' effect. Also, the negative association between negative life events and GD was stronger in those with high neuroticism. Multivariable analyses with individual life events showed that a few strong independent effects remained for each dimension.

LIMITATIONS

Life event reports were retrospective; only three outcome dimensions were used.

CONCLUSIONS

These results show that the effects of life events and modifying factors depend, to an extent, on the symptom domain that is considered as outcome, illustrating the need to account for symptom heterogeneity in etiological life event research.

The impact of individual depressive symptoms on impairment of psychosocial functioning

Previous studies have established that scores on Major Depressive Disorder scales are correlated with measures of impairment of psychosocial functioning. It remains unclear, however, whether individual depressive symptoms vary in their effect on impairment, and if so, what the magnitude of these differences might be. We analyzed data from 3,703 depressed outpatients in the first treatment stage of the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) study. Participants reported on the severity of 14 depressive symptoms, and stated to what degree their depression impaired psychosocial functioning (in general, and in the five domains work, home management, social activities, private activities, and close relationships). We tested whether symptoms differed in their associations with impairment, estimated unique shared variances of each symptom with impairment to assess the degree of difference, and examined whether symptoms had variable impacts across impairment domains. Our results show that symptoms varied substantially in their associations with impairment, and contributed to the total explained variance in a range from 0.7% (hypersomnia) to 20.9% (sad mood). Furthermore, symptoms had significantly different impacts on the five impairment domains. Overall, sad mood and concentration problems had the highest unique associations with impairment and were among the most debilitating symptoms in all five domains. Our findings are in line with a growing chorus of voices suggesting that symptom sum-scores obfuscate relevant differences between depressed patients and that substantial rewards will come from close attention to individual depression symptoms.

Specific dysphoric symptoms are predicted by early maladaptive schemas

Early maladaptive schemas (EMSs) are cognitive patterns resulting from unmet core emotional needs in childhood that have been linked to the development of psychopathology. As depression is a multifaceted phenomenon, we hypothesized that specific dysphoric symptoms would be predicted by different EMSs. Four hundred and fifty-six participants completed a measure of EMSs (Young Schema Questionnaire) and reported on the severity of the symptoms of criterion A for major depression in DSM-IV during the occurrence of a dysphoric episode in the previous 12 months. A series of stepwise multiple regression analyses were performed to investigate the predictive power of the EMSs for the severity of each specific depressive symptom. When controlling for gender and current levels of depression, specific symptoms were predicted by different EMSs: sadness by Negativity/Pessimism; anhedonia by Failure; self-harm by Emotional Deprivation and Vulnerability to Harm or Illness; worthlessness by Failure and Negativity/Pessimism; psychomotor retardation/restlessness by Vulnerability to Harm or Illness and Entitlement/Grandiosity; and poor concentration by Insufficient Self-Control/Self-Discipline. The more physical symptoms of fatigue, insomnia/hypersomnia, and appetite loss/appetite gain were not predicted by any of the EMSs. Although the cross-sectional design of the study does not allow for conclusions about the direction of effects, results suggest that depression is not a unitary phenomenon and provide a possible explanation for previous inconsistent findings.

The evolutionary puzzle of suicide

Mechanisms of self-destruction are difficult to reconcile with evolution’s first rule of thumb: survive and reproduce. However, evolutionary success ultimately depends on inclusive fitness. The altruistic suicide hypothesis posits that the presence of low reproductive potential and burdensomeness toward kin can increase the inclusive fitness payoff of self-removal. The bargaining hypothesis assumes that suicide attempts could function as an honest signal of need. The payoff may be positive if the suicidal person has a low reproductive potential. The parasite manipulation hypothesis is founded on the rodent—Toxoplasma gondii host-parasite model, in which the parasite induces a “suicidal” feline attraction that allows the parasite to complete its life cycle. Interestingly, latent infection by T. gondii has been shown to cause behavioral alterations in humans, including increased suicide attempts. Finally, we discuss how suicide risk factors can be understood as nonadaptive byproducts of evolved mechanisms that malfunction. Although most of the mechanisms proposed in this article are largely speculative, the hypotheses that we raise accept self-destructive behavior within the framework of evolutionary theory.

Evolutionary mechanisms for loneliness

Robert Weiss (1973) conceptualised loneliness as perceived social isolation, which he described as a gnawing, chronic disease without redeeming features. On the scale of everyday life, it is understandable how something as personally aversive as loneliness could be regarded as a blight on human existence. However, evolutionary time and evolutionary forces operate at such a different scale of organisation than we experience in everyday life that personal experience is not sufficient to understand the role of loneliness in human existence. Research over the past decade suggests a very different view of loneliness than suggested by personal experience, one in which loneliness serves a variety of adaptive functions in specific habitats. We review evidence on the heritability of loneliness and outline an evolutionary theory of loneliness, with an emphasis on its potential adaptive value in an evolutionary timescale.

Affective neuronal selection: the nature of the primordial emotion systems

Based on studies in affective neuroscience and evolutionary psychiatry, a tentative new proposal is made here as to the nature and identification of primordial emotional systems. Our model stresses phylogenetic origins of emotional systems, which we believe is necessary for a full understanding of the functions of emotions and additionally suggests that emotional organizing systems play a role in sculpting the brain during ontogeny. Nascent emotional systems thus affect cognitive development. A second proposal concerns two additions to the affective systems identified by Panksepp. We suggest there is substantial evidence for a primary emotional organizing program dealing with power, rank, dominance, and subordination which instantiates competitive and territorial behavior and is an evolutionary contributor to self-esteem in humans. A program underlying disgust reactions which originally functioned in ancient vertebrates to protect against infection and toxins is also suggested.

Reappraising the relationship between maternal age and postpartum depression according to the evolutionary theory: Empirical evidence from a survey in primary health services

BACKGROUND

Postpartum depression (PPD) is a widespread worldwide phenomenon, but its etiology remains unclear. This study reappraised how evolutionary theory could explain PPD as an adaptation through investigating the relationship between maternal age and PPD, and if this relationship is modified according to the number of children at home.

METHODS

A cross-sectional study carried out in five primary health care units included 811 participants randomly selected among mothers of children up to five postpartum months in Rio de Janeiro, Brazil. Postpartum depression was defined by scores above 11 on Edinburgh Postnatal Depression Scale (EPDS), and statistical analysis was based on multivariate logistic regression models.

RESULTS

One hundred and ninety-seven (24.3%, CI 95% 21.3-27.2) participants were classified as PPD positives. Maternal age was significantly associated to PPD (OR=0.96, p-value=0.019) independently of socioeconomic and reproductive characteristics, conjugal status or substance consumption by the couple. Thus, for each additional year, a reduction of 4% in the chance of developing PPD could be anticipated, effect which was not modified by the number of children at home (p-value=0.602).

LIMITATIONS

Information on social support was not included in this analysis since its relationship with maternal mental health would be better evaluated in a prospective fashion.

CONCLUSIONS

These findings suggest that adaptive mechanisms shaped through human generations persist contributing to the development of PPD in contemporary societies. According to this evolutionary approach, as maternal age advances the reproductive potential diminishes and, consequently, mothers are less prone to develop PPD and reduce investment in new offspring.

The role of personal goals in depressive reaction to adverse life events: a cross-sectional study

Consistent with cognitive views of depression, we aimed to investigate the mediating role of personal goals in the relationship between stressful events and distinct patterns of depressive symptoms in a nonclinical sample. Participants identified a dysphoric episode that occurred in the previous year by reporting the severity of 12 depressive symptoms and their plausible cause. A goal taxonomy was used to determine how much the event interfered with the achievement of a series of personal goals. After controlling for age and current level of depression, the patterns of symptoms differed based on the triggering events. The relationship between sadness and affective losses was partially mediated by the personal goal of lovableness, and success was a partial mediator in the association between an event of failure and symptoms of worthlessness and anhedonia. Although the cross-sectional design of the study does not allow for conclusions on the direction of effects, findings suggest the importance of motivational factors in the development of specific patterns of depressive symptoms to adverse events. Assuming a continuum from low mood to clinical depression, treatment models could benefit from a precise identification of the specific stressors that initiate depressive behaviour and the personal meaning assigned to those events.