Contributions of Polygenic Risk and Disease Status to Gray Matter Abnormalities in Major Depression

BACKGROUND

Gray matter (GM) abnormalities in depression are potentially attributable to some combination of trait, state, and illness history factors. Here, we sought to determine the contributions of polygenic risk for depression, depressive disease status, and the interaction of these factors to these GM abnormalities.

METHODS

We conducted a cross-sectional comparison using a 2 × 3 factorial design examining effects of polygenic risk for depression (lower vs. upper quartile) and depression status (never depressed, currently depressed, or remitted depression) on regional GM concentration and GM volume. Participants were a subset of magnetic resonance imaging-scanned UK Biobank participants comprising 2682 people (876 men, 1806 women) algorithmically matched on 16 potential confounders.

RESULTS

In women but not men, we observed that elevated polygenic risk for depression was associated with reduced cerebellar GM volume. This deficit occurred in salience and dorsal attention network regions of the cerebellum and was associated with poorer performance on tests of attention and executive function but not fluid intelligence. Moreover, in women with current depression compared to both women with remitted depression and women who never had depression, we observed GM reductions in ventral and medial prefrontal, insular, and medial temporal regions. These state-related abnormalities remained when accounting for antidepressant medication status.

CONCLUSIONS

Neuroanatomical deficits attributed broadly to major depression are more likely due to an aggregation of independent factors. Polygenic risk for depression accounted for cerebellar structural abnormalities that themselves accounted for cognitive deficits observed in this disorder. Medial and ventral prefrontal, insular, and temporal cortex deficits constituted a much larger proportion of the aggregate deficit and were attributable to the depressed state.

Trait- and state-like co-activation pattern dynamics in current and remitted major depressive disorder

BACKGROUND

Distinguishing between trait- and state-like neural alternations in major depressive disorder (MDD) may advance our understanding of this recurring disorder. We aimed to investigate dynamic functional connectivity alternations in unmedicated individuals with current or past MDD using co-activation pattern analyses.

METHODS

Resting-state functional magnetic resonance imaging data were acquired from individuals with first-episode current MDD (cMDD, n = 50), remitted MDD (rMDD, n = 44), and healthy controls (HCs, n = 64). Using a data-driven consensus clustering technique, four whole-brain states of spatial co-activation were identified and associated metrics (dominance, entries, transition frequency) were analyzed with respect to clinical characteristics.

RESULTS

Relative to rMDD and HC, cMDD showed increased dominance and entries of state 1 (primarily involving default mode network (DMN)), and decreased dominance of state 4 (mostly involving frontal-parietal network (FPN)). Among cMDD, state 1 entries correlated positively with trait rumination. Conversely, relative to cMDD and HC, individuals with rMDD were characterized by increased state 4 entries. Relative to HC, both MDD groups showed increased state 4-to-1 (FPN to DMN) transition frequency but reduction in state 3 (spanning visual attention, somatosensory, limbic networks), with the former metric specifically related to trait rumination.

LIMITATIONS

Further confirmation with longitudinal studies are required.

CONCLUSIONS

Regardless of symptoms, MDD was characterized by increased FPN-to-DMN transitions and reduced dominance of a hybrid network. State-related effect emerged in regions critically implicated in repetitive introspection and cognitive control. Asymptomatic individuals with past MDD were uniquely linked to increased FPN entries. Our findings identify trait-like brain network dynamics that might increase vulnerability to future MDD.

Understanding and predicting future relapse in depression from resting state functional connectivity and self-referential processing

BACKGROUND

The recurrent nature of Major Depressive Disorder (MDD) asks for a better understanding of mechanisms underlying relapse. Previously, self-referential processing abnormalities have been linked to vulnerability for relapse. We investigated whether abnormalities in self-referential cognitions and functioning of associated brain-networks persist upon remission and predict relapse.

METHODS

Remitted recurrent MDD patients (n = 48) and never-depressed controls (n = 23) underwent resting-state fMRI scanning at baseline and were additionally assessed for their implicit depressed self-associations and ruminative behaviour. A template-based dual regression approach was used to investigate between-group differences in default mode, cingulo-opercular and frontoparietal network resting-state functional connectivity (RSFC). Additional prediction of relapse status at 18-month follow-up was investigated within patients using both regression analyses and machine learning classifiers.

RESULTS

Remitted patients showed higher rumination, but no implicit depressed self-associations or RSFC abnormalities were observed between patients and controls. Nevertheless, relapse was related to i) baseline RSFC between the ventral default mode network and the precuneus, dorsomedial frontal gyrus, and inferior occipital lobe, ii) implicit self-associations, and iii) uncontrollability of ruminative thinking, when controlled for depressive symptomatology. Moreover, preliminary machine learning classifiers demonstrated that RSFC within the investigated networks predicted relapse on an individual basis.

CONCLUSIONS

Remitted MDD patients seem to be commonly characterized by abnormal rumination, but not by implicit self-associations or abnormalities in relevant brain networks. Nevertheless, relapse was predicted by self-related cognitions and default mode RSFC during remission, suggesting that variations in self-relevant processing play a role in the complex dynamics associated with the vulnerability to developing recurrent depressive episodes.

CLINICAL TRIAL REGISTRATION

Netherlands Trial Register, August 18, 2015, trial number NL53205.042.15.

Potential structural trait markers of depression in the form of alterations in the structures of subcortical nuclei and structural covariance network properties

It has been proposed recently that major depressive disorder (MDD) could represent an adaptation to conserve energy after the perceived loss of an investment in a vital source, such as group identity, personal assets, or relationships. Energy conserving behaviors associated with MDD may form a persistent marker in brain regions and networks involved in cognition and emotion regulation. In this study, we examined whether subcortical regions and volume-based structural covariance networks (SCNs) have state-independent alterations (trait markers). First-episode drug-naïve currently depressed (cMDD) patients (N = 131), remitted MDD (RD) patients (N = 67), and healthy controls (HCs, N = 235) underwent structural magnetic resonance imaging (MRI). Subcortical gray matter volumes (GMVs) were calculated in FreeSurfer software, and group differences in GMVs and SCN were analyzed. Compared to HCs, major findings were decreased GMVs of left pallidum and pulvinar anterior of thalamus in the cMDD and RD groups, indicative of a trait marker. Relative to HCs, subcortical SCNs of both cMDD and RD patients were found to have reduced small-world-ness and path length, which together may represent a trait-like topological feature of depression. In sum, the left pallidum, left pulvinar anterior of thalamus volumetric alterations may represent trait marker and reduced small-world-ness, path length may represent trait-like topological feature of MDD.

Converging evidence for enduring perceptions of low social status in individuals in remission from depression

BACKGROUND

The risk of depressive relapse and recurrence is associated with social risk factors that may be amplified by a submissive socio-cognitive profile.

METHODS

In Study 1 we aimed to identify perceptions of low social status in a community sample (N = 613) with a self-reported history of mental health difficulties (n = 232) and, more specifically in Study 2 (N = 122), in individuals in clinical remission from depression (n = 18), relative to a never-depressed control group (n = 64), and relative to a group experiencing a current depressive episode (n = 40).

RESULTS

In Study 1, a total of 225 of the 232 participants in the self-reported mental health difficulties group opted to provide further information regarding their mental health history, of whom 153 (68%) reported a history of anxiety, 168 (74.7%) reported a history of depression, and 13 (5.8%) reported an unspecified mental health history. Elevated depressive symptoms were associated with perceptions of low social status which significantly differed between individuals with and without a self-reported history of mental health difficulties. In Study 2 we found enduring perceptions of low social status in remitted depressed individuals.

LIMITATIONS

We were unable to discern between historical or current clinical diagnosis in the community sample of Study 1, as we were reliant on self-report. We were unable to explore the effects of medication or causal relationships between depressive symptoms and social status as the studies were cross-sectional in nature.

CONCLUSIONS

These findings suggest that evolutionarily rooted socio-cognitive profiles could impact affiliative processes and may confer increased vulnerability to future depressive episodes.

State-independent and -dependent structural alterations in limbic-cortical regions in patients with current and remitted depression

BACKGROUND

The high recurrence of major depressive disorder (MDD) may derive from underlying state-independent structural alterations.

METHODS

First-episode drug-naïve currently depressed (cMDD) patients (N = 97), remitted depressed (RD) patients (N = 72), and healthy controls (HCs, N = 100) underwent structural magnetic resonance imaging (MRI). Group differences in cortical thickness (CT), surface area (SA), and local gyrification index (lGI) were analyzed in FreeSurfer.

RESULTS

Both groups of depressed patients had significantly decreased CT, relative to HCs, in the left precentral gyrus and significantly increased lGI values in the left superior frontal gyrus (SFG) indicative of state-independent alterations. Relative to HCs, the cMDD group had decreased CT of the SFG, caudal middle frontal gyrus (MFG), posterior cingulate cortex (PCC), and lateral occipital regions as well as increased SA or lGI of the superior temporal gyrus, precuneus, and pericalcarine, whereas the RD group had increased SA or lGI of the SFG, caudal MFG, and supramarginal gyrus; these alterations appeared to be state-dependent. SA or lGI values of the fusiform gyrus, inferior temporal gyrus, and superior parietal lobule differed between the cMDD and RD groups, consistent with state-dependent alterations. Beck depression inventory scores correlated with CT or lGI values of the caudal MFG, lateral occipital cortex in depressed patients.

LIMITATIONS

The structural features of several subcortical limbic regions were not analyzed.

CONCLUSIONS

Left precentral gyrus CT and left SFG gyrification alterations may represent state-independent alterations in MDD.

Topologically state-independent and dependent functional connectivity patterns in current and remitted depression

OBJECTIVE

Identification of state-independent and -dependent neural biomarkers may provide insight into the pathophysiology and effective treatment of major depressive disorder (MDD), therefore we aimed to investigate the state-independent and -dependent topological alterations of MDD.

METHOD

Brain resting-state functional magnetic resonance imaging (fMRI) data were acquired from 59 patients with unmedicated first episode current MDD (cMDD), 48 patients with remitted MDD (rMDD) and 60 demographically matched healthy controls (HCs). Using graph theory, we systematically studied the topological organization of their whole-brain functional networks at the global and nodal level.

RESULTS

At a global level, both patient groups showed decreased normalized clustering coefficient in relative to HCs. On a nodal level, both patient groups showed decreased nodal centrality, predominantly in cortex-mood-regulation brain regions including the dorsolateral prefrontal cortex, posterior parietal cortex and posterior cingulate cortex. By comparison to cMDD patients, rMDD group had a higher nodal centrality in right parahippocampal gyrus.

LIMITATIONS

The present study, an exploratory analysis, may require further confirmation with task-based and experimental studies.

CONCLUSIONS

Deficits in the topological organization of the whole brain and cortex-mood-regulation brain regions in both rMDD and cMDD represent state-independent biomarkers.

State-independent alterations of intrinsic brain network in current and remitted depression

BACKGROUND

It has been proposed that state-independent, or trait, neurobiological alterations across illness phases may contribute to the high recurrence of major depressive disorder (MDD). Although intrinsic brain network abnormalities have been implicated consistently in MDD neuropathology, MDD state-independent and -dependent resting-state network alterations have not been clearly studied.

METHODS

Resting-state functional magnetic resonance imaging (fMRI) data were collected from 57 medication-naive first-episode current MDD patients, 35 remitted MDD patients, and 66 healthy controls (HCs). Independent component analysis (ICA) was used to extract subnetworks of the default mode network (DMN), central executive network (CEN), and salience network (SN).

RESULTS

Relative to HCs, the current MDD and remitted MDD groups had decreased intra-intrinsic functional connectivity (iFC) in the dorsal lateral prefrontal cortex (dlPFC) of the left CEN, increased inter-FC between the SN and right CEN (rCEN), and decreased inter-FC between the anterior DMN (aDMN) and rCEN. The altered intra-iFC in the left CEN were correlated negatively with the depressive level in the remitted MDD.

CONCLUSIONS

Hypoactivity of the dlPFC in the left CEN, increased inter-FC between the SN and rCEN, and decreased inter-FC between the aDMN and rCEN may reflect state-independent biomarkers of MDD.

Differential engagement of cognitive control regions and subgenual cingulate based upon presence or absence of comorbid anxiety with depression

BACKGROUND

Major depressive disorder (MDD) and anxiety disorders are highly comorbid, sharing many similar symptoms, including impairments in cognitive control. Deficits in cognitive control could be a potential mechanism underlying impaired emotion regulation in mood disorders.

METHODS

Participants were 44 individuals with no history of mental illness (healthy controls, HC), 31 individuals in the remitted state of MDD (rMDD), and 18 individuals who met lifetime DSM-IV-TR criteria for rMDD and an anxiety disorder in remission (Comorbid). Participants completed a Parametric Go/No-Go (PGNG) test during fMRI. Event-related analyses modeled activity for cognitive control successes (Hits for Targets, Rejections for Lures) and failures (Commissions on Lures) on the PGNG task.

RESULTS

The rMDD group showed significantly reduced activity within the cognitive control network (CCN) during Commission errors, including the middle frontal gyrus and inferior parietal lobule (IPL). The Comorbid group showed significantly reduced activity in several clusters within the CCN during correct Rejections, including the left IPL and right inferior frontal gyrus and greater subgenual cingulate. Notably, during correct Rejections, 60% of activation for the Comorbid group was within the Salience and Emotion Network (SEN), with 0% within the CCN.

LIMITATIONS

The size of the Comorbid subgroup was modest, preventing subanalysis of the different AD subtypes.

CONCLUSIONS

There is evidence that CCN activity declines in rMDD and that there may be compensatory SEN activity in individuals with Comorbid rMDD and anxiety. Our findings support the identification of comorbid anxiety as a meaningful subtype of MDD that may obscure group differences between rMDD and HCs.

Temperamental factors in remitted depression: The role of effortful control and attentional mechanisms

BACKGROUND

Temperamental effortful control and attentional networks are increasingly viewed as important underlying processes in depression and anxiety. However, it is still unknown whether these factors facilitate depressive and anxiety symptoms in the general population and, more specifically, in remitted depressed individuals.

METHODS

We investigated to what extent effortful control and attentional networks (i.e., Attention Network Task) explain concurrent depressive and anxious symptoms in healthy individuals (n = 270) and remitted depressed individuals (n = 90). Both samples were highly representative of the US population.

RESULTS

Increased effortful control predicted a substantial decrease in symptoms of both depression and anxiety in the whole sample, whereas decreased efficiency of executive attention predicted a modest increase in depressive symptoms. Remitted depressed individuals did not show less effortful control nor less efficient attentional networks than healthy individuals. Moreover, clinical status did not moderate the relationship between temperamental factors and either depressive or anxiety symptoms.

LIMITATIONS

Limitations include the cross-sectional nature of the study.

CONCLUSIONS

Our study shows that temperamental effortful control represents an important transdiagnostic process for depressive and anxiety symptoms in adults.

The role of cognitive impairment in psychosocial functioning in remitted depression

BACKGROUND

Cognitive dysfunction is a prevalent and disabling symptom of Major Depressive Disorder (MDD), and is often retained in the remitted stage of illness. Emerging evidence suggests that cognitive impairment may be associated with dysfunction in a number of psychosocial domains (e.g., workplace productivity, social relationships). The current study explored the relationship between cognition and psychosocial functioning in remitted MDD and in healthy controls.

METHODS

Data were obtained from 182 participants of the Cognitive Function and Mood Study (CoFaM-S), a cross-sectional study of cognition, mood, and social cognition in mood disorders. Participants' (Remitted MDD n = 72, Healthy n = 110) cognition was assessed with a battery of cognitive tests including the Repeatable Battery for the Assessment of Neuropsychological Function (RBANS) and other standard measures of cognition (e.g., The Tower of London task). Psychosocial functioning was clinically evaluated with the Functioning Assessment Short Test (FAST).

RESULTS

The results indicated that executive functioning was the strongest independent predictor of functioning in remitted MDD patients, whereas various cognitive domains predicted psychosocial functioning in healthy individuals.

LIMITATIONS

Psychosocial functioning was measured with a clinical interview, and was therefore reliant on clinicians' judgement of impairment, as opposed to more objective measures of functioning.

CONCLUSIONS

These findings suggest that executive cognition plays an important role in functional recovery in remitted depression, and may be a crucial target in adjunctive treatment.

Alleviated negative rather than positive attentional bias in patients with depression in remission: an eye-tracking study

Objective To investigate attentional bias toward happy and sad faces in remitted depressed (RD) patients compared with healthy control (HC) subjects. Methods This cross-sectional study enrolled RD patients and sex- and age-matched HC subjects. Eye movement data were acquired for all study participants while free viewing a 2 × 2 matrix of emotional faces. The attentional bias toward different emotional faces and whether the attention maintenance components generated attentional bias in the RD patients were analysed by comparing the attentional modes of the RD group with the HC group. Results A total of 27 RD patients and 27 HC subjects were analysed in this study. The RD and HC groups exhibited no significant differences toward first fixation location and initial attentional maintenance. In later attentional maintenance, the RD group showed significantly less attentional bias toward happy faces, but there were no significant differences in their attentional bias toward sad faces, compared with the HC group. Conclusions This present study showed that the negative attentional bias of RD patients was successfully eased, but their positive attentional bias was still insufficient.

Temporal changes in attention to sad and happy faces distinguish currently and remitted depressed individuals from never depressed individuals

Depression is associated with attentional biases for emotional information that are proposed to reflect stable vulnerability factors for the development and recurrence of depression. A key question for researchers is whether those who have recovered from depression also exhibit attentional biases, and if so, how similar these biases are to those who are currently depressed. To address this question, the present study examined attention to emotional faces in remitted depressed (N=26), currently depressed (N=16), and never depressed (N=33) individuals. Participants viewed sets of four face images (happy, sad, threatening, and neutral) while their eye movements were tracked throughout an 8-s presentation. Like currently depressed participants, remitted depressed participants attended to sad faces significantly more than never depressed participants and attended to happy faces significantly less. Analyzing temporal changes in attention revealed that currently and remitted depressed participants did not reduce their attention to sad faces over the 8-s presentation, unlike never depressed participants. In contrast, remitted depressed participants attended to happy faces similarly to never depressed participants, increasing their attention to happy faces over the 8-s presentation. The implications for cognitive theories of depression and depression vulnerability are discussed.

Effects of mood and rumination on cortisol levels in daily life: an ambulatory assessment study in remitted depressed patients and healthy controls

The influence of naturally occurring emotional and cognitive experiences on hypothalamic-pituitary-adrenal axis (HPAA) activity is still underinvestigated, particularly in clinical populations. The present study examined effects of mood and rumination on cortisol levels in daily life in remitted depressed patients with recurrent episodes or a chronic precourse (n=31) and healthy controls (n=32). Ambulatory assessment of subjective variables (valence, calmness, energetic-arousal, ruminative self-focus), daily stressors, and saliva cortisol samples was performed five times a day on two consecutive workdays, whereby cortisol was collected 20min after the subjective assessments. In addition, depressive symptoms and trait rumination (brooding, reflection) were measured retrospectively. Multilevel models revealed that remitted depressed patients showed lower cortisol activity compared to healthy controls. Depressive symptoms and trait rumination did not predict HPAA activity, whereas, by controlling for daily stressors, higher daily means of ruminative self-focus and lower daily means of valence, energetic arousal and calmness were associated with higher daily cortisol levels. Separate analyses per group revealed that mean daily ruminative self-focus predicted higher cortisol in both samples. In contrast, lower daily means of calmness, but also of valence and energetic arousal, were significantly linked to higher cortisol output only in healthy controls, but not in the patient sample. These findings indicate that naturally occurring rumination and low mood are associated with increased activation of the HPAA in daily life. Moreover, our data revealed a potentially reduced mood-cortisol coupling in remitted recurrent depression, possibly indicating that during the course of recurrent depression HPAA activation might become less responsive toward subtle emotional experiences in natural contexts.