Cortical grey matter reductions associated with treatment-resistant chronic unipolar depression. Controlled magnetic resonance imaging study

Anomalous gray matter structural networks in major depressive disorder

BACKGROUND

Major depressive disorder (MDD) is characterized by abnormalities in structure, function, and connectivity in several brain regions. Few studies have examined how these regions are organized in the brain or investigated network-level structural aberrations that might be associated with depression.

METHODS

We used graph analysis to examine the gray matter structural networks of individuals diagnosed with MDD (n = 93) and a demographically similar healthy comparison group (n = 151) with no history of psychopathology. The efficiency of structural networks for processing information was determined by quantifying local interconnectivity (clustering) and global integration (path length). We also compared the groups on the contributions of high-degree nodes (i.e., hubs) and regional network measures, including degree (number of connections in a node) and betweenness (fraction of short path connections in a node).

RESULTS

Depressed participants had significantly decreased clustering in their brain networks across a range of network densities. Compared with control subjects, depressed participants had fewer hubs primarily in medial frontal and medial temporal areas, had higher degree in the left supramarginal gyrus and right gyrus rectus, and had higher betweenness in the right amygdala and left medial orbitofrontal gyrus.

CONCLUSIONS

Networks of depressed individuals are characterized by a less efficient organization involving decreased regional connectivity compared with control subjects. Regional connections in the amygdala and medial prefrontal cortex may play a role in maintaining or adapting to depressive pathology. This is the first report of anomalous large-scale gray matter structural networks in MDD and provides new insights concerning the neurobiological mechanisms associated with this disorder.

Saliva cortisol and male depressive syndrome in a community study. The Sudurnesjamenn study

BACKGROUND

The degree and direction of hypothalamic-pituitary-adrenal (HPA) dysfunction to male mental health is unclear.

AIMS

The aim of the study was to investigate the relationship between cortisol and male mental health.

METHODS

In this community study, 534 males were screened, using the Beck Depression Inventory (BDI), Gotland Male Depression Scale (GMDS) and a general health questionnaire. Those with signs of depression (n = 65) and controls (n = 69) were evaluated in a psychiatric examination according to the DSM-IV criteria for depressive disorder (DD). In a sub-sample (n = 51) saliva cortisol was measured five times on a single day.

RESULTS

Evening cortisol was significantly higher in untreated individuals with DD. Significantly higher evening cortisol (at 22 h) correlated also with a history of physical disorder, a history of any mental disorder and MADRS score ≥ 20 (Montgomery-Åsberg Depression Rating Scale). High cortisol, measured as AUC (area under curve), correlated with a high MADRS score but not with any other health variable tested. Morning cortisol did not correlate with any health variable; however, cortisol awakening response (CAR) could not be investigated. The BDI and GMDS scores did not correlate with cortisol measurements.

CONCLUSION

Evening saliva cortisol measurement seems most informative, as it correlates with male depressive syndrome in our study but replications with larger studies are needed.

Antidepressant effects of sertraline associated with volume increases in dorsolateral prefrontal cortex

BACKGROUND

Structural brain imaging has revealed differences in gray matter volume between depressed individuals and control subjects in key structures related to emotion. The aim of the present study was to assess within subjects whether regional changes in gray matter volume were observed over time in depressed patients treated with sertraline.

METHODS

Thirteen depressed patients were assigned to selective serotonin reuptake inhibitor (SSRI) treatment with sertraline. Structural magnetic resonance imaging (MRI) was performed at four time points over 12 weeks of treatment. Depressed individuals were compared to a control group of 10 subjects scanned at the same time points using voxel based morphometry and a statistical growth modeling technique.

RESULTS

SSRI-treated patients showed a region of significantly increasing gray matter volume over time within the left dorsolateral prefrontal cortex (DLPFC) that specifically correlated with decreases in self-reported depression levels. No statistically significant changes were observed related to time in controls.

LIMITATIONS

This study included a small sample size and the method of analysis was capable of detecting only linear changes in volume.

CONCLUSIONS

Effective antidepressant treatment with sertraline is associated with left DLPFC volume increases. These volume increases may reflect cortical architectural changes associated with top-down neuronal modulation of emotion.

Feasibility of studying brain morphology in major depressive disorder with structural magnetic resonance imaging and clinical data from the electronic medical record: a pilot study

For certain research questions related to long-term outcomes or to rare disorders, designing prospective studies is impractical or prohibitively expensive. Such studies could instead utilize clinical and magnetic resonance imaging data (MRI) collected as part of routine clinical care, stored in the electronic medical record (EMR). Using major depressive disorder (MDD) as a disease model, we examined the feasibility of studying brain morphology and associations with remission using clinical and MRI data exclusively drawn from the EMR. Advanced automated tools were used to select MDD patients and controls from the EMR who had brain MRI data, but no diagnosed brain pathology. MDD patients were further assessed for remission status by review of clinical charts. Twenty MDD patients (eight full-remitters, six partial-remitters, and six non-remitters), and 15 healthy control subjects met all study criteria for advanced morphometric analyses. Compared to controls, MDD patients had significantly smaller right rostral-anterior cingulate volume, and level of non-remission was associated with smaller left hippocampus and left rostral-middle frontal gyrus volume. The use of EMR data for psychiatric research may provide a timely and cost-effective approach with the potential to generate large study samples reflective of the real population with the illness studied.

Gray matter volume in major depressive disorder: a meta-analysis of voxel-based morphometry studies

We designed this study to perform a meta-analysis of gray matter (GM) findings in major depressive disorder (MDD) by using the signed differential mapping (SDM) toolbox. The Pubmed, ScienceDirect and Scopus databases were searched, and only studies published or published online before November 2010 have been included. Twenty voxel-based morphometry (VBM) studies of adult MDD patients were entered in the meta-analysis by SDM toolbox with threshold criteria set as error probability less than 0.00005 and cluster more than 50 voxels. Onset age, numbers of patients and controls, gender ratio of both groups, ratio of medicated patients, depression rating scores, illness duration, co-morbidity and existence of corrected p value were also meta-regressed as covariates to exclude confounding biases. Voxel-wise meta-analytic results of these 20 VBM studies in MDD patients revealed that GM deficits were observed in the right anterior cingulate cortex and left anterior cingulate cortex when patients were compared with controls. The findings remained mostly unchanged in jackknife sensitivity analyses. The potential confounding factors had little impact on the results. This meta-analysis suggested GM deficits of the anterior cingulate cortex might be important in the etiology of MDD.

Quest for biomarkers of treatment-resistant depression: shifting the paradigm toward risk

The search for potential biomarkers of psychiatric disorders is a central topic in biological psychiatry. This review concerns published studies on potential biomarkers of treatment-resistant depression (TRD). The search for biomarkers of TRD in the bloodstream has focused on cytokines and steroids as well as brain-derived neurotropic factor. Additional approaches to identifying biomarkers of TRD have dealt with cerebrospinal fluid analysis, magnetic resonance imaging, and positron emission tomography. Some studies have also investigated potential genetic and epigenetic factors in TRD. Most studies have, however, used a post hoc experimental design that failed to determine the association between biomarkers and the initial risk of TRD. Particular attention in future studies should be on shifting the experimental paradigm toward procedures that can determine the risk for developing treatment resistance in untreated depressed individuals.

Depression uncouples brain hate circuit

It is increasingly recognized that we need a better understanding of how mental disorders such as depression alter the brain's functional connections to improve both early diagnosis and therapy. A new holistic approach has been used to investigate functional connectivity changes in the brains of patients suffering from major depression using resting-state functional magnetic resonance imaging (fMRI) data. A canonical template of connectivity in 90 different brain regions was constructed from healthy control subjects and this identified a six-community structure with each network corresponding to a different functional system. This template was compared with functional networks derived from fMRI scans of both first-episode and longer-term, drug resistant, patients suffering from severe depression. The greatest change in both groups of depressed patients was uncoupling of the so-called 'hate circuit' involving the superior frontal gyrus, insula and putamen. Other major changes occurred in circuits related to risk and action responses, reward and emotion, attention and memory processing. A voxel-based morphometry analysis was also carried out but this revealed no evidence in the depressed patients for altered gray or white matter densities in the regions showing altered functional connectivity. This is the first evidence for the involvement of the 'hate circuit' in depression and suggests a potential reappraisal of the key neural circuitry involved. We have hypothesized that this may reflect reduced cognitive control over negative feelings toward both self and others.

Sex and stress hormone influences on the expression and activity of brain-derived neurotrophic factor

The neurotrophin, brain-derived neurotrophic factor (BDNF), is recognized as a key component in the regulation of CNS ontogeny, homeostasis and adult neuroplasticity. The importance of BDNF in CNS development and function is well documented by numerous reports from animal studies linking abnormal BDNF signaling to metabolic disturbances and anxiety or depressive-like behavior. Despite the diverse roles for BDNF in nearly all aspects of CNS physiology, the regulation of BDNF expression, as well as our understanding of the signaling mechanisms associated with this neurotrophin, remains incomplete. However, links between sex hormones such as estradiol and testosterone, as well as endogenous and synthetic glucocorticoids (GCs), have emerged as important mediators of BDNF expression and function. Examples of such regulation include brain region-specific induction of Bdnf mRNA in response to estradiol. Additional studies have also documented regulation of the expression of the high-affinity BDNF receptor Tropomyosin-Related Kinase B by estradiol, thus implicating sex steroids not only in the regulation of BDNF expression, but also in mechanisms of signaling associated with it. In addition to gonadal steroids, further evidence also suggests functional interaction between BDNF and GCs, such as in the regulation of corticotrophin-releasing hormone and other important neuropeptides. In this review, we provide an overview of the roles played by selected sex or stress hormones in the regulation of BDNF expression and signaling in the CNS.

Enhancing synaptic plasticity and cellular resilience to develop novel, improved treatments for mood disorders

There is mounting evidence that recurrent mood disorders - once considered “good prognosis diseases”- are, in fact, often very severe and life-threatening illnesses. Furthermore, although mood disorders have traditionally been conceptualized as neurochemical disorders, there is now evidence from a variety of sources demonstrating regional reductions in central nervous system (CNS) volume, as well as reductions in the numbers and/or sizes ofglia and neurons in discrete brain areas. Although the precise cellular mechanisms underlying these morphometric changes remain to be fully elucidated, the data suggest that mood disorders are associated with impairments of synaptic plasticity and cellular resilience. In this context, it is noteworthy that there is increasing preclinical evidence that antidepressants regulate the function of the glutamatergic system. Moreover, although clearly preliminary, the available clinical data suggest that attenuation of N-methyl-D-aspartate (NMDA) function has antidepressant effects. Recent preclinical and clinical studies have shown that signaling pathways involved in regulating cell survival and cell death are long-term targets for the actions of antidepressant agents. Antidepressants and mood stabilizers indirectly regulate a number of factors involved in cell survival pathways, including cyclic adenosine monophosphate (cAMP) response element binding protein (CREB), brain-derived neurotrophic factor (BDNF), the antiapoptotic protein bcl-2, and mitogen-activated protein (MAP) kinases, and may thus bring about some of their delayed long-term beneficial effects via underappreciated neurotrophic effects. There is much promise for the future development of treatments that more directly target molecules in critical CNS signaling pathways regulating synaptic plasticity and cellular resilience. These will represent improved long-term treatments for mood disorders.

Cellular abnormalities in depression: evidence from postmortem brain tissue

During the past two decades, in vivo neuroimaging studies have permitted significant insights into the general location of dysfunctional brain regions in depression. In parallel and often intersecting ways, neuroanatomical, pharmacological, and biochemical studies of postmortem brain tissue are permitting new insights into the pathophysiology of depression. In addition to long-recognized neurochemical abnormalities in depression, novel studies at the microscopic level support the contention that mood disorders are associated with abnormalities in cell morphology and distribution. In the past 6 years, cell-counting studies have identified changes in the density and size of both neurons and glia in a number of frontolimbic brain regions, including dorsolateral prefrontal, orbitofrontal, and anterior cingulate cortex, and the amygdala and hippocampus. Convergence of cellular changes at the microscopic level with neuroimaging changes detected in vivo provides a compelling integration of clinical and basic research for disentangling the pathophysiology of depression. The ultimate integration of these two research approaches will occur with premortem longitudinal clinical studies on well-characterized patients linked to postmortem studies of the same subjects.

Neuroplasticity in mood disorders

Neuroimaging and neuropathological studies of major depressive disorder (MDD) and bipolar disorder (BD) have identified abnormalities of brain structure in areas of the prefrontal cortex, amygdala, striatum, hippocampus, parahippocampal gyrus, and raphe nucleus. These structural imaging abnormalities persist across illness episodes, and preliminary evidence suggests they may in some cases arise prior to the onset of depressive episodes in subjects at high familial risk for MDD. In other cases, the magnitude of abnormality is reportedly correlated with time spent depressed. Postmortem histopathological studies of these regions have shown abnormal reductions of synaptic markers and glial cells, and, in rare cases, reductions in neurons in MDD and BD. Many of the regions affected by these structural abnormalities show increased glucose metabolism during depressive episodes. Because the glucose metabolic signal is dominated by glutamatergic transmission, these data support other evidence that excitatory amino acid transmission is elevated in limbic-cortical-striatal-pallidal-thalamic circuits during depression. Some of the subject samples in which these metabolic abnormalities have been demonstrated were also shown to manifest abnormally elevated stressed plasma cortisol levels. The co-occurrence of increased glutamatergic transmission and Cortisol hypersecretion raises the possibility that the gray matter volumetric reductions in these depressed subjects are partly accounted for by processes homologous to the dendritic atrophy induced by chronic stress in adult rodents, which depends upon interactions between elevated glucocorticoid secretion and N-meihyl-D-aspartate (NMDA)-glutamate receptor stimulation. Some mood-stabilizing and antidepressant drugs that exert neurotrophic effects in rodents appear to reverse or attenuate the gray matter volume abnormalities in humans with mood disorders. These neurotrophic effects may be integrally related to the therapeutic effects of such agents, because the regions affected by structural abnormalities in mood disorders are known to play major roles in modulating the endocrine, autonomic, behavioral, and emotional experiential responses to stressors.

Is depression in Parkinson's disease (PD) a specific entity?

BACKGROUND

Clinical lore and research have suggested for a long time that depression and PD are closely related. We examined the validity of depression associated with PD (dPD) as a specific subtype of depression according to face validity, descriptive validity, construct validity and predictive validity.

METHODS

The English literature was reviewed after searching the MEDLINE database up to June 2010.

RESULTS

There appears to be three possible subtypes of comorbid depression: 1) patients who would have been depressed even if they had no PD (nonspecific-casual comorbid dPD), 2) patients who would have been depressed if they had had another disabling medical illness (nonspecific-reactive comorbid dPD) 3) those for which depression is directly related to the underlying pathophysiology of PD (specific comorbid dPD). These latter patients may more often present with particular clinical characteristics (descriptive validity): absence of history of depression or only within 5 years prior to onset of PD, absence of guilty thoughts and self-blame, absence of suicidal behavior, right-sided onset. However, dPD is only partly responsive to dopamine replacement and cannot be solely explained by dopamine deficiency. Other neurotransmitter systems are affected in PD and are involved in the pathophysiology of dPD. Their relative involvement however may differ from that in idiopathic depression (i.e.: lesser involvement of serotonergic systems).

LIMITATIONS

Therapeutic data are limited to few controlled trials.

CONCLUSIONS

Further research may allow differential diagnosis between dPD subtypes (i.e.: those who do and do not result from the underlying pathophysiological process of PD) and help inform treatment choice.

Cerebrospinal fluid space alterations in melancholic depression

Melancholic depression is a biologically homogeneous clinical entity in which structural brain alterations have been described. Interestingly, reports of structural alterations in melancholia include volume increases in Cerebro-Spinal Fluid (CSF) spaces. However, there are no previous reports of CSF volume alterations using automated whole-brain voxel-wise approaches, as tissue classification algorithms have been traditionally regarded as less reliable for CSF segmentation. Here we aimed to assess CSF volumetric alterations in melancholic depression and their clinical correlates by means of a novel segmentation algorithm (‘new segment’, as implemented in the software Statistical Parametric Mapping-SPM8), incorporating specific features that may improve CSF segmentation. A three-dimensional Magnetic Resonance Image (MRI) was obtained from seventy patients with melancholic depression and forty healthy control subjects. Although imaging data were pre-processed with the ‘new segment’ algorithm, in order to obtain a comparison with previous segmentation approaches, tissue segmentation was also performed with the ‘unified segmentation’ approach. Melancholic patients showed a CSF volume increase in the region of the left Sylvian fissure, and a CSF volume decrease in the subarachnoid spaces surrounding medial and lateral parietal cortices. Furthermore, CSF increases in the left Sylvian fissure were negatively correlated with the reduction percentage of depressive symptoms at discharge. None of these results were replicated with the ‘unified segmentation’ approach. By contrast, between-group differences in the left Sylvian fissure were replicated with a non-automated quantification of the CSF content of this region. Left Sylvian fissure alterations reported here are in agreement with previous findings from non-automated CSF assessments, and also with other reports of gray and white matter insular alterations in depressive samples using automated approaches. The reliable characterization of CSF alterations may help in the comprehensive characterization of brain structural abnormalities in psychiatric samples and in the development of etiopathogenic hypotheses relating to the disorders.

Multi-centre diagnostic classification of individual structural neuroimaging scans from patients with major depressive disorder

Quantitative abnormalities of brain structure in patients with major depressive disorder have been reported at a group level for decades. However, these structural differences appear subtle in comparison with conventional radiologically defined abnormalities, with considerable inter-subject variability. Consequently, it has not been possible to readily identify scans from patients with major depressive disorder at an individual level. Recently, machine learning techniques such as relevance vector machines and support vector machines have been applied to predictive classification of individual scans with variable success. Here we describe a novel hybrid method, which combines machine learning with feature selection and characterization, with the latter aimed at maximizing the accuracy of machine learning prediction. The method was tested using a multi-centre dataset of T(1)-weighted 'structural' scans. A total of 62 patients with major depressive disorder and matched controls were recruited from referred secondary care clinical populations in Aberdeen and Edinburgh, UK. The generalization ability and predictive accuracy of the classifiers was tested using data left out of the training process. High prediction accuracy was achieved (~90%). While feature selection was important for maximizing high predictive accuracy with machine learning, feature characterization contributed only a modest improvement to relevance vector machine-based prediction (~5%). Notably, while the only information provided for training the classifiers was T(1)-weighted scans plus a categorical label (major depressive disorder versus controls), both relevance vector machine and support vector machine 'weighting factors' (used for making predictions) correlated strongly with subjective ratings of illness severity. These results indicate that machine learning techniques have the potential to inform clinical practice and research, as they can make accurate predictions about brain scan data from individual subjects. Furthermore, machine learning weighting factors may reflect an objective biomarker of major depressive disorder illness severity, based on abnormalities of brain structure.

Gray matter differences between healthy and depressed adolescents: a voxel-based morphometry study

BACKGROUND

Major depressive disorder (MDD) frequently begins during adolescence and is associated with significant morbidity and mortality. However, little is known about the neurobiology of adolescent depression. A better understanding of the neurobiology will be helpful in developing more effective preventive and treatment interventions for this highly disabling illness.

METHODS

Using a voxel-based morphometric method, the study compared gray matter and white matter volumes in 22 adolescents with MDD and 22 age- and gender-matched normal controls.

RESULTS

Compared with controls, depressed adolescents had smaller gray matter volume in the frontal lobe and caudate nucleus bilaterally and right superior and middle temporal gyri. However, the groups did not differ significantly on white matter volume.

CONCLUSIONS

These findings in depressed adolescents are consistent with the previous findings of gray matter abnormalities in frontolimbic areas and the striatum in depressed adults and suggest the presence of these structural changes at the onset of depressive illness.

Annual research review: progress in using brain morphometry as a clinical tool for diagnosing psychiatric disorders

Brain morphometry in recent decades has increased our understanding of the neural bases of psychiatric disorders by localizing anatomical disturbances to specific nuclei and subnuclei of the brain. At least some of these disturbances precede the overt expression of clinical symptoms and possibly are endophenotypes that could be used to diagnose an individual accurately as having a specific psychiatric disorder. More accurate diagnoses could significantly reduce the emotional and financial burden of disease by aiding clinicians in implementing appropriate treatments earlier and in tailoring treatment to the individual needs. Several methods, especially those based on machine learning, have been proposed that use anatomical brain measures and gold-standard diagnoses of participants to learn decision rules that classify a person automatically as having one disorder rather than another. We review the general principles and procedures for machine learning, particularly as applied to diagnostic classification, and then review the procedures that have thus far attempted to diagnose psychiatric illnesses automatically using anatomical measures of the brain. We discuss the strengths and limitations of extant procedures and note that the sensitivity and specificity of these procedures in their most successful implementations have approximated 90%. Although these methods have not yet been applied within clinical settings, they provide strong evidence that individual patients can be diagnosed accurately using the spatial pattern of disturbances across the brain.

Increased hippocampal volumes in lithium treated adolescents with bipolar disorders: a structural MRI study

BACKGROUND

Structural neuroimaging studies in bipolar disorder (BD) have consistently identified several anatomical abnormalities in many brain areas related to mood regulation. Hippocampus is one of the key components of emotional regulatory networks in the brain. Evidence about hippocampal changes in BD is quite limited and inconsistent particularly for adolescent onset BD. It is aimed to compare hippocampus volumes of euthymic BD-I adolescents with healthy controls using structural MRI.

METHODS

Hippocampal volumes of seventeen youths between 13 and 19 age period with DSM-IV BD (seven boys) and twelve healthy comparison subjects (five boys) were compared using structural MRI. Differences in hippocampal volumes between groups were tested.

RESULTS

There was no significant difference between the right and left hippocampus volumes of patients with BD and the control group. However boys tended to have significantly larger right hippocampal volumes than girls both in BD and control group. Right hippocampal volumes were enlarged in lithium treated bipolar patients. This enlargement is not related to sex.

LIMITATIONS

Future, longitudinal follow-up studies need large enough sample sizes of both sexes and a sex-matched healthy comparison group to sort out developmental, gender and medication influences on brain structures over time in BD.

CONCLUSIONS

Lithium treatment in adolescent-onset BD has a significant effect on hippocampus volumes.

Gray matter abnormalities in Major Depressive Disorder: a meta-analysis of voxel based morphometry studies

BACKGROUND

Voxel-based morphometry (VBM) has been widely used to quantify structural brain changes associated with Major Depressive Disorder (MDD). While some consistent findings have been reported, individual studies have also varied with respect to the key brain regions affected by the illness, and how these abnormalities are related to patients' clinical characteristics. Here, we aimed to identify those brain regions that most consistently showed gray matter anomalies in MDD, and their clinical correlates, using meta-analytic techniques.

METHODS

A systematic search of VBM studies was applied in MDD. Signed differential mapping, a new coordinate based neuroimaging meta-analysis technique, was applied to data collated from a total of 23 studies comparing regional gray matter volumes of 986 MDD patients and 937 healthy controls.

RESULTS

Gray matter was significantly reduced in a confined cluster located in the rostral anterior cingulate cortex (ACC). There were also gray matter reductions in dorsolateral and dorsomedial prefrontal cortex and decrease in the latter region was evident in patients with multiple-episodes. Amygdala and parahippocampal gray matter volumes were significantly reduced in studies including patients with comorbid anxiety disorders, as well as in first-episode/drug free samples.

CONCLUSIONS

Gray matter reduction in rostral ACC was the most consistent finding in VBM studies of MDD. The evidence for reductions in other regions within fronto-subcortical and limbic regions was less consistent. The associations between these gray matter anomalies and clinical characteristics, particularly measures relating to illness duration, suggest that chronic MDD has a robust and deleterious, albeit spatially focal, effect on brain structure.

Subchronic treatment with aldosterone induces depression-like behaviours and gene expression changes relevant to major depressive disorder

The potential role of aldosterone in the pathophysiology of depression is unclear. The aim of this study was to test the hypothesis that prolonged elevation of circulating aldosterone induces depression-like behaviour accompanied by disease-relevant changes in gene expression in the hippocampus. Subchronic (2-wk) treatment with aldosterone (2 μg/100 g body weight per day) or vehicle via subcutaneous osmotic minipumps was used to induce hyperaldosteronism in male rats. All rats (n = 20/treatment group) underwent a modified sucrose preference test. Half of the animals from each treatment group were exposed to the forced swim test (FST), which served both as a tool to assess depression-like behaviour and as a stress stimulus. Affymetrix microarray analysis was used to screen the entire rat genome for gene expression changes in the hippocampus. Aldosterone treatment induced an anhedonic state manifested by decreased sucrose preference. In the FST, depressogenic action of aldosterone was manifested by decreased latency to immobility and increased time spent immobile. Aldosterone treatment resulted in transcriptional changes of genes in the hippocampus involved in inflammation, glutamatergic activity, and synaptic and neuritic remodelling. Furthermore, aldosterone-regulated genes substantially overlapped with genes affected by stress in the FST. This study demonstrates the existence of a causal relationship between the hyperaldosteronism and depressive behaviour. In addition, aldosterone treatment induced changes in gene expression that may be relevant to the aetiology of major depressive disorder. Subchronic treatment with aldosterone represents a new animal model of depression, which may contribute to the development of novel targets for the treatment of depression.

Voxelwise meta-analysis of gray matter reduction in major depressive disorder

BACKGROUND

Voxel-based morphometry (VBM) has been widely used in studies of major depressive disorder (MDD) and has provided cumulative evidence of gray matter abnormalities in patients relative to controls. Thus we performed a meta-analysis to integrate the reported studies to determine the consistent gray matter alterations in MDD.

METHODS

A systematic search was conducted to identify VBM studies which contrasted MDD patients against a comparison group. The coordinates of gray matter change across studies were meta-analyzed using the activation likelihood estimation (ALE) method hybridized with the rank-based Genome Scan Meta-Analysis (GSMA) to quantitatively estimate regional gray matter reductions in MDD.

RESULTS

A total of 20 VBM studies comparing 543 major depressive patients with 750 healthy control subjects were included. Consistent gray matter reductions in all MDD patients relative to healthy controls were identified in the bilateral anterior cingulate cortex (ACC), right middle and inferior frontal gyrus, right hippocampus and left thalamus.

CONCLUSIONS

Meta-analysis of all primary VBM studies indicates that significant gray matter reductions in MDD are localized in a distributed neural network which includes frontal, limbic and thalamic regions. Future studies will benefit from the use of a longitudinal approach to examine anatomical and functional abnormalities within this network and their relationship to clinical profile, particularly in first-episode and drug-naive MDD patients.

Prediction of illness severity in patients with major depression using structural MR brain scans

PURPOSE

To develop a model for the prediction of Major Depressive Disorder (MDD) illness severity ratings from individual structural MRI brain scans.

MATERIALS AND METHODS

Structural T1-weighted MRI scans were obtained from 30 patients with MDD recruited from two different scanning centers. Self-rated (Beck Depression Inventory; BDI), and clinician-rated (Hamilton Rating Scale for Depression, HRSD), syndrome-specific illness severity ratings were obtained just before scanning. Relevance vector regression (RVR) was used to predict the scores (BDI, HRSD) from T1-weighted MRI scans.

RESULTS

It was possible to predict the BDI score (correlation between actual score and RVR predicted scores r = 0.694; P < 0.0001), but not the HRSD scores (r = 0.34; P = 0.068) from individual subjects. BDI scores from the most ill patients were predicted more accurately than those from patients who were least ill (standard deviation of difference between predicted and actual scores 2.5 versus 7.4, respectively).

CONCLUSION

These data suggest that T1-weighted MRI scans contain sufficient information about neurobiological change in patients with MDD to permit accurate predictions about illness severity, on an individual subject basis, particularly for the most ill patients.

Structural neuroimaging studies in major depressive disorder. Meta-analysis and comparison with bipolar disorder

CONTEXT

Although differences in clinical characteristics exist between major depressive disorder (MDD) and bipolar disorder (BD), consistent structural brain abnormalities that distinguish the disorders have not been identified.

OBJECTIVES

To investigate structural brain changes in MDD using meta-analysis of primary studies; assess the effects of medication, demographic, and clinical variables; and compare the findings with those of a meta-analysis of studies on BD.

DATA SOURCES

The MEDLINE, EMBASE, and PsycINFO databases were searched for studies from January 1, 1980, to February 2, 2010.

STUDY SELECTION

Two hundred twenty-five studies that used magnetic resonance imaging or x-ray computed tomography to compare brain structure in patients with MDD with that of controls were included in an online database, and 143 that measured common brain structures were selected for meta-analysis.

DATA EXTRACTION

Twenty-five variables, including demographic and clinical data, were extracted from each study, when available. For the meta-analysis, mean structure size and standard deviation were extracted for continuous variables, and the proportion of patients and controls with an abnormality in brain structure was extracted for categorical variables.

DATA SYNTHESIS

Compared with the structure of a healthy brain, MDD was associated with lateral ventricle enlargement; larger cerebrospinal fluid volume; and smaller volumes of the basal ganglia, thalamus, hippocampus, frontal lobe, orbitofrontal cortex, and gyrus rectus. Patients during depressive episodes had significantly smaller hippocampal volume than patients during remission. Compared with BD patients, those with MDD had reduced rates of deep white matter hyperintensities, increased corpus callosum cross-sectional area, and smaller hippocampus and basal ganglia. Both disorders were associated with increased lateral ventricle volume and increased rates of subcortical gray matter hyperintensities compared with healthy controls.

CONCLUSIONS

The meta-analyses revealed structural brain abnormalities in MDD that are distinct from those observed in BD. These findings may aid investigators attempting to discriminate mood disorders using structural magnetic resonance imaging data.

Demonstration of decreased gray matter concentration in the midbrain encompassing the dorsal raphe nucleus and the limbic subcortical regions in major depressive disorder: an optimized voxel-based morphometry study

BACKGROUND

Previous neuroimaging studies in patients with major depressive disorder (MDD) have reported changes in several brain areas, such as the medial and dorsolateral orbital cortex, amygdala, hippocampus, and basal ganglia. However, the results of these studies are inconsistent, and relatively few studies have been conducted using voxel-based morphometry (VBM) to detect gray matter concentration (GMC) abnormalities in patients with MDD.

METHODS

We examined 47 MDD patients and 51 healthy controls to investigate structural abnormalities using a 1.5 T magnetic resonance imaging system, which was normalized to a customized T1 template and segmented with optimized VBM. Analysis of covariance with age and gender as covariates was adopted for the VBM statistics; the level of statistical significance was set at P<0.05 for the corrected false discovery rate.

RESULTS

Decreased GMC was found in MDD patients in the bilateral amygdalae, hippocampi, fusiform gyri, lingual gyri, insular gyri, middle-superior temporal gyri, thalami, cingulate gyri, the central lobule of the cerebellum, and the midbrain encompassing the dorsal raphe nuclei (DRN).

LIMITATIONS

Half of our study subjects were taking antidepressants. This may have been a potential confounding factor if any of the medications affected cortical volume.

CONCLUSIONS

The results suggest that the GMC of several regions associated with emotion regulation was lower in MDD patients. In particular, we found decreased GMC in the DRN. These findings may provide a better understanding of the anatomical properties of the neural mechanisms underlying the etiology of MDD.

Symptom relief and facilitation of emotional processing

Symptoms and observable signs offer an important way of measuring the severity of depression and estimating recovery. However, a shift to understanding the cognitive neuroscience underlying the clinical picture has been fruitful and could change the approach in meaningful ways. Cognition as defined by attention, memory and executive function is impaired in depression and offers a way of identifying abnormal brain states or structure. Moreover, such changes may limit functional recovery and explain why recurrent depression in particular is so impairing. More subtle aspects of cognition can be revealed by studies of emotional processing. Patients with depression have negative emotional biases but the measurement of such effects is confounded by the global impairments already described and may be secondary to a primary change in mood. Nevertheless, there are early effects of antidepressants treatments in healthy volunteers and depressed patients on such mechanisms specifically. It remains to be established how far the properties of antidepressants are defined by such effects both in relation to successful treatment and in their potential for emotional side effects, or blunting of experience, after recovery from depressive symptoms.

Mechanisms of antidepressant action: an integrated dopaminergic perspective

The molecular mechanisms that cause and maintain the major depressive disorder (MDD) are currently unknown. Consistently, antidepressant treatments are characterized by insufficient success rates. This causes high social costs and severe personal sufferings. In the present review we analyze some of the paradigms that are used to explain MDD, particularly from the perspective of the dopaminergic (DA) system. DA has been more classically associated with psychosis and substance abuse disorders, even though a role of DA in MDD has been proposed as well and some antidepressants with DA profile exist. In the present work, we review some of the molecular mechanisms that underpin MDD from the perspective of the dopaminergic system, in the hope of unifying some of the major theories of MDD - the monoaminergic, inflammatory, epigenetics, neurotrophin and anti-apoptotic theories. Several shared components of these theories are highlighted, partially accounted by the functions of the DA system (see supplementary video).

Disrupted regional homogeneity in treatment-resistant depression: a resting-state fMRI study

BACKGROUND

Using a newly developed regional homogeneity (ReHo) approach, we were to explore the features of brain activity in patients with treatment-resistant depression (TRD) in resting state, and further to examine the relationship between abnormal brain activity in TRD patients and specific symptom factors derived from ratings on the Hamilton Rating Scale for Depression (HRSD).

METHODS

24 patients with TRD and 19 gender-, age-, and education-matched healthy subjects participated in the fMRI scans.

RESULTS

1. Compared with healthy controls, decreased ReHo were found in TRD patients in the left insula, superior temporal gyrus, inferior frontal gyrus, lingual gyrus and cerebellumanterior lobe (culmen) (p<0.05, corrected). 2. Compared with healthy controls, increased ReHo were found in the left superior temporal gyrus, cerebellum posterior lobe (tuber), cerebellum anterior lobe (culmen), the right cerebellar tonsil and bilateral fusiform gyrus (p<0.05, corrected). 3. There was no correlation between the ReHo values in any brain region detected in our study and the patients' age, years of education, illness duration, HRSD total score and its symptom factors.

LIMITATION

The influence of antidepressants to the brain activity in TRD patients was not fully eliminated.

CONCLUSIONS

The pathogenesis of TRD may be attributed to abnormal neural activity in multiple brain regions.

Sertoli cell therapy: a novel possible treatment strategy for treatment-resistant major depressive disorder

By the year 2020, depression will be the 2nd most common health problem in the world. Current medications to treat depression are effective in less than 50% of patients. There is the need for novel treatments for depression to address the high rates of resistance to current treatment and the chronic residual symptoms in many patients treated for depression. The heterogeneity of major depressive disorder suggests that multiple neurocircuits and neurochemicals are involved in its pathogenesis thus, finding an alternative to neurotransmitter agonist- or antagonist-based treatments offers an important new approach. Cellular therapy is an emerging treatment strategy for multiple diseases, including depression. Based upon their in vivo function as "nurse cells" within the testis and the documented viability, efficacy, and safety of Sertoli cells transplanted into multiple tissues, including brain, the potential for these cells to provide a neuroprotective, anti-inflammatory, and trophic environment for neurons should be considered. It is proposed that the combination of self-protective, immunoregulatory and trophic properties of Sertoli cells may confer a unique potential for depression treatment and avoid many of the risks and challenges associated with stem cell therapies. At the very least, studies of the effects of Sertoli cell transplantation will add substantially to our understanding of the cellular and molecular processes that underlie depression.

Medical comorbidity in recurrent versus first-episode depressive patients

OBJECTIVE

This study compares the comorbidity of affective disorders and medical diseases in primary care patients with either a first or recurrent depressive episode.

METHOD

A cross-sectional epidemiological study in primary care centres in Spain was designed. A total of 10,257 primary care patients suffering a DSM-IV major depressive episode (MDD) were analysed. Depression was assessed using the Montgomery-Asberg Depression Rating Scale (MADRS), and World Health Organization (WHO) medical diagnoses were provided by the patient's general practitioner according to medical records revised on the basis of radiology or laboratory test data.

RESULTS

A total of 88.6% of recurrent patients and 71.1% of first-episode depressive patients reported a medical condition (aOR = 2.61, CI = 2.31-2.93). All medical conditions were more prevalent in the recurrent group than in first-episode group, and with the exception of myocardial infarction, psoriasis and migraine, all other crude ORs showed statistically significant differences between first- and recurrent episodes patients after adjusting for gender, age, education, socioeconomic status and body mass index (BMI).

CONCLUSION

Recurrent depression is associated with a decrement in health that is significantly greater than in first-episode depression. Special attention needs to be paid to the physical health in the middle- and long-term management of patients with affective disorders.

Longitudinal MR study of brain structure and hippocampus volume in major depressive disorder

OBJECTIVE

To determine whether long-term course of treated major depression has an effect on the structure of the brain and the hippocampal volume.

METHOD

An 11-year follow-up procedure was used with data collection at baseline and again at follow-up. Tensor-based morphometry (TBM) and automatic hippocampal volume measure was performed on different datasets. The baseline dataset consisted of T1-weighted magnetic resonance images (MRIs) of 24 in-patients suffering from major depression and 33 healthy controls. The second dataset consisted of T1-weighted MRIs of 31 remitted depressive patients and 36 healthy controls. The longitudinal dataset consisted of 19 patients and 19 matched healthy controls present at both the first and the second dataset. Brain segmentation and hippocampal segmentation were fully automated and were based on a spatial normalization to the International Consortium of Brain Mapping (ICBM) non-linear model.

RESULTS

Depressed patients were found to have smaller temporal lobes bilaterally, medulla and right hippocampus at baseline. However, these changes were not found at follow-up 11 years later. Moreover, these changes did not significantly correlate with the illness outcome.

CONCLUSION

Brain structure changes seem to be state dependent in major depression, only occurring in acute episode of major depression and normalizing after remission.

The hippocampus in major depression: evidence for the convergence of the bench and bedside in psychiatric research?

Major depressive disorder (MDD) has until recently been conceptualized as an episodic disorder associated with 'chemical imbalances' but no permanent brain changes. Evidence has emerged in the past decade that MDD is associated with small hippocampal volumes. This paper reviews the clinical and biological correlates of small hippocampal volumes based on literature searches of PubMed and EMBASE and discusses the ways in which these data force a re-conceptualization of MDD. Preclinical data describe the molecular and cellular effects of chronic stress and antidepressant treatment on the hippocampus, providing plausible mechanisms through which MDD might be associated with small hippocampal volumes. Small hippocampal volumes are associated with poor clinical outcome and may be a mechanism through which MDD appears to be a risk factor for Alzheimer's disease. The pathways through which stress may be linked to MDD, the emergence of chronicity or treatment resistance in MDD and the association between MDD and memory problems may be at least partially understood by dissecting the association with depression and changes in the hippocampus. MDD must be re-conceived as a complex illness, associated with persistent morphological brain changes that are detectable before illness onset and which may be modified by clinical and treatment variables.

The moderating effect of the APOE [small element of] 4 allele on the relationship between hippocampal volume and cognitive decline in older depressed patients

OBJECTIVE

the apolipoprotein E epsilon-4 (APOE [small element of] 4) allele and depression are independently associated with increased risk for cognitive decline (CD). The authors have reported that depressed elders with an APOE [small element of]4 allele had greater CD compared with depressed elders without the allele. Depression affects the hippocampus, and reduced hippocampal volume has been associated with CD. This study sought to examine in depressed patients the relationships between hippocampal volume, the APOE [small element of] 4 allele, and their interaction on CD. Analyses were performed to examine the influence of baseline hippocampal volume, the APOE [small element of] 4 allele, and their interactions on change in cognitive functioning overtime.

DESIGN

secondary data analysis using linear regression analyses.

SETTING

clinical Research Center for the Study of Depression in Later Life conducted at Duke University.

PARTICIPANTS

depressed older patients (N = 61) followed up for 4 years.

MEASURES

At baseline, cognitive functioning (assessed by the Mini-Mental State Examination), left and right hippocampal volume (assessed by magnetic resonance imaging), and APOE genotype were obtained. At 4-year follow-up, cognitive functioning was reassessed.

RESULTS

the APOE [small element of] 4 allele and left hippocampal volume, but not right hippocampal volume, were independently associated with CD. Importantly, the authors found the APOE [small element of]4 allele to moderate the effects of left hippocampal volume on CD. The APOE [small element of]4 allele seemed to have little effect among those with larger left hippocampal volumes, whereas the allele influenced CD among those with smaller hippocampal volumes.

CONCLUSION

future studies of cognitive impairment and decline should examine both individual and conjoint effects of putative risk factors.

Temporal lobe atrophy and white matter lesions are related to major depression over 5 years in the elderly

The influence of organic brain changes on the development of depression in the elderly is uncertain. Cross-sectional studies, most often from clinical samples, report associations with brain atrophy and cerebrovascular disease, while longitudinal population studies have given mixed results. Our aim was to investigate whether cortical atrophy and white matter lesions (WMLs) on computed tomography (CT) predict occurrence of depression in the elderly. This is a prospective population-based study with 5-year follow-up. The baseline sample included 525 elderly subjects, aged 70-86 years, without dementia or major depression, with a score on the Mini-Mental State Examination above 25, and without dementia at follow-up. Cortical atrophy and WMLs were evaluated at baseline using CT. The main outcome measure was development of major or minor depression at follow-up according to Diagnostic and Statistical Manual of Mental Disorders, fourth edition, as evaluated using neuropsychiatric examinations and hospital discharge registers. Logistic regression was used to estimate risk. Over the period of 5 years, 20 individuals developed major and 63 minor depression. Presence of temporal lobe atrophy (odds ratio (OR)=2.81, 95% confidence interval (CI) 1.04-7.62) and moderate-to-severe WMLs (OR=3.21, 95% CI 1.00-10.26) independently predicted major, but not minor, depression after controlling for various confounders. Other brain changes did not predict occurrence of depression. Our findings suggest that temporal lobe atrophy and WMLs represent relatively independent and complementary pathways to major depression in the elderly. This may have implications for prevention, as both neurodegeneration and cerebrovascular disease have been related to preventable factors.

The hypothalamic-pituitary-adrenal axis and serotonin abnormalities: a selective overview for the implications of suicide prevention

Suicidal behavior and mood disorders are one of the world's largest public health problems. The biological vulnerability for these problems includes genetic factors involved in the regulation of the serotonergic system and stress system. The hypothalamic-pituitary-adrenal (HPA) axis is a neuroendocrine system that regulates the body's response to stress and has complex interactions with brain serotonergic, noradrenergic and dopaminergic systems. Corticotropin-releasing hormone and vasopressin act synergistically to stimulate the secretion of ACTH that stimulates the biosynthesis of corticosteroids such as cortisol from cholesterol. Cortisol is a major stress hormone and has effects on many tissues, including on mineralocorticoid receptors and glucocorticoid receptors in the brain. Glucocorticoids produce behavioral changes, and one important target of glucocorticoids is the hypothalamus, which is a major controlling center of the HPA axis. Stress plays a major role in the various pathophysiological processes associated with mood disorders and suicidal behavior. Serotonergic dysfunction is a well-established substrate for mood disorders and suicidal behavior. Corticosteroids may play an important role in the relationship between stress, mood changes and perhaps suicidal behavior by interacting with 5-HT1A receptors. Abnormalities in the HPA axis in response to increased levels of stress are found to be associated with a dysregulation in the serotonergic system, both in subjects with mood disorders and those who engage in suicidal behavior. HPA over-activity may be a good predictor of mood disorders and perhaps suicidal behavior via abnormalities in the serotonergic system.

High-frequency rTMS treatment increases left prefrontal myo-inositol in young patients with treatment-resistant depression

BACKGROUND

Neuroimaging studies suggest that the prefrontal cortex (PFC) is involved in the pathophysiology of major depression. Repetitive transcranial magnetic stimulation (rTMS) as an antidepressant intervention has increasingly been investigated in the last two decades. In this study metabolic changes within PFC of severely depressed patients before and after rTMS were evaluated by proton magnetic resonance spectroscopy (1H-MRS).

METHOD

Thirty-four young depressed patients with treatment-resistant unipolar depression were enrolled in a double-blind, randomized study active ((n=19) vs. sham(n=15)), and the PFC was investigated before and after high-frequency (15 Hz) rTMS using 3-tesla proton magnetic resonance spectroscopy. Response was defined as a 50% reduction of the Hamilton depression rating scale. The results were compared with 28 age- and gender-matched healthy controls.

RESULTS

In depressive patients a significant reduction in myo-inositol (m-Ino) was observed pre-rTMS (p<0.001). After successful treatment, m-Ino increased significantly in left PFC and the levels no longer differed from those of age-matched controls. In addition to a positive correlation between clinical improvement and an increment in m-Ino ratio, a correlation between clinical improvement and early age onset was observed.

CONCLUSIONS

Our results support the notion that major depressive disorder is accompanied by state-dependent metabolic alterations, especially in myo-inositol metabolism, which can be partly reversed by successful rTMS.

Orbitofrontal volume reductions during emotion recognition in patients with major depression

BACKGROUND

Major depressive disorder is associated with both structural and functional alterations in the emotion regulation network of the central nervous system. The relation between structural and functional changes is largely unknown. Therefore, we sought to determine the relation between structural differences and functional alterations during the recognition of emotional facial expressions.

METHODS

We examined 13 medication-free patients with major depression and 15 healthy controls by use of structural T1-weighted high-resolution magnetic resonance imaging (MRI) and functional MRI during 1 session. We set the statistical threshold for the analysis of imaging data to p < 0.001 (uncorrected).

RESULTS

As shown by voxel-based morphometry, depressed patients had reductions in orbitofrontal cortex volume and increases in cerebellar volume. Additionally, depressed patients showed increased activity during emotion recognition in the middle frontal cortex, caudate nucleus, precuneus and lingual gyrus. Within this cerebral network, the orbitofrontal volumes were negatively correlated in depressed patients but not in healthy controls with changes in blood oxygen level-dependent signal in the middle frontal gyrus, caudate nucleus, precuneus and supplementary motor area.

LIMITATIONS

Our results are limited by the relatively small sample size.

CONCLUSIONS

This combined functional and structural MRI study provides evidence that the orbitofrontal cortex is a key area in major depression and that structural changes result in functional alterations within the emotional circuit. Whether these alterations in the orbitofrontal cortex are also related to persistent emotional dysfunction in remitted mental states and, therefore, are related to the risk of depression needs further exploration.

Theory of mind deficits in chronically depressed patients

BACKGROUND

Poor theory of mind (ToM) performance has been found in patients with mood disorders, but it has not been examined in the subgroup of chronic depression where ToM deficits may be even more persistent than in acute depressive episodes. The aim of this study was to compare the ToM performance of chronically depressed patients with a healthy control group and to clarify the relation of ToM to other cognitive functions.

METHODS

ToM performance was assessed in 30 chronically depressed patients and 30 matched healthy controls by two cartoon picture story tests. In addition, logical memory, alertness, and executive functioning were evaluated.

RESULTS

Chronically depressed patients were markedly impaired in all ToM- and neuropsychological tasks compared to healthy controls. Performance in the different ToM tests was significantly correlated with at least one other cognitive variable. After controlling for logical memory and working memory, no ToM tasks predicted being a patient.

CONCLUSIONS

Patients with chronic depression present significant deficits in "reading" social interactions, which may be associated with general cognitive impairments.

Neuropsychophysiological correlates of depression

The neuropsychiatric and cognitive deficits have been shown to exist in various psychiatric disorders. An attempt has been made by authors to evaluate the evidence pertaining to electrophysiological, structural and neuropsychological domains in depression. Renewal of interest in testing patients with depression on a broad range of neuropsychological tasks has revealed distinct pattern of cognitive impairment in cases with depression. The review focuses on structural and neuropsychological evidence of deficit in cases of depression.

A longitudinal study of cognitive function in melancholic and non-melancholic subtypes of major depressive disorder

BACKGROUND

Research concerning cognition in depression has often yielded inconsistent findings. The presence of mixed melancholic and non-melancholic subtypes of major depressive disorder (MDD) in most previous research may explain some of the contradictory results (Hickie, 1996).

METHODS

This longitudinal study compared the cognitive performance of people with melancholic (n=17) and non-melancholic (n=17) MDD admitted to one of two university hospitals. Participants received an extensive clinical and cognitive assessment at admission and again 3 months after recovery and discharge.

RESULTS

Overall, participants with melancholia had selective memory deficits with broader impairment of executive control skills. Specifically, after correcting for depression severity, they performed more poorly on tests requiring memory acquisition, mental flexibility, set-shifting, selective attention, concept-formation and multi-tasking compared to those with non-melancholic depression. These deficits were present at both assessments suggesting that the increased initial severity of cognitive deficits for those with melancholia mean that they require a longer time to recovery.

LIMITATIONS

The clinical homogeneity of the study sample may underestimate the extent of cognitive impairment for those presenting with comorbid illness and/or significant drug/alcohol histories.

CONCLUSIONS

These findings indicate that the depressed group with melancholia have a distinctly different and more impaired cognitive profile to those without melancholic features and suggest that these clinical subtypes should be considered separately in future research concerning MDD. Furthermore, the melancholic group appears to require longer periods for cognitive recovery and this has implications for return to work and daily functioning following clinical discharge.

Hippocampus, glucocorticoids and neurocognitive functions in patients with first-episode major depressive disorders

The aim of this study was to determine whether there was any relationship between hippocampal volume, and glucocorticoid regulation, and cognitive dysfunctions in drug-naïve major depressive disorder (MDD) patients during their first episode. Twenty drug-free female MDD patients in their first episode and 15 healthy females as control subjects were included in the study. All subjects underwent 3.0 Tesla (T) magnetic resonance imaging (MRI), comprehensive neuropsychological testing and dexamethasone suppression tests (DST). The volumes of the right and left hippocampus of the patients were found to be significantly smaller than those of the controls. Patients were found to have significantly lower scores on measures of attention, working memory, psychomotor speed, executive functions, and visual and verbal memory fields. The performance of the patients only in the recollection memory and memory of reward-associated rules were positively correlated with hippocampal volumes. The volumes of the left and right hippocampus did not correlate with basal or post-dexamethasone cortisol levels. Our findings indicate that depressed patients have smaller hippocampi even in the earlier phase of their illness. Further research efforts are needed to explain the mechanisms that are responsible for the small hippocampus in depressed patients.

The impact of treatment on HPA axis activity in unipolar major depression

Dysregulation of hypothalamic-pituitary-adrenal axis activity in major depressive disorder has been found to normalize with successful treatment, though inconsistencies exist. To determine the magnitude of change in cortisol levels from pre to post-treatment in individuals with unipolar depression quantitative methods of meta-analysis were applied. Thirty-four studies met inclusion criteria and consisted of a total of 1049 depressed patients across study samples. The overall mean effect size of pre-post-treatment cortisol measures indicated that approximately 56% of depressed participants had similar cortisol levels before and after treatment regardless of symptom improvement. The mean effect size of pre-post cortisol measures for those who responded to treatment was larger than the mean effect size of non-responders; however, this difference did not reach statistical significance. As well, no significant differences in mean effect size of pre-post cortisol measures based on type of treatment (e.g. antidepressant vs. ECT) were found. Subtype of depressive illness and length of treatment may contribute to the magnitude of change in cortisol measure before and after treatment. Inconsistent findings within the reviewed literature may confound the overall results. The type of treatment and response to treatment do not appear to impact the magnitude of change in cortisol level pre to post-treatment. Our findings suggest that the utility of cortisol as an outcome measure may be limited to specific subsets of the depressed population, and that given the variability in HPA results between studies, it is premature to state that cortisol is not a good outcome measure.

Brain volume abnormalities in major depressive disorder: a meta-analysis of magnetic resonance imaging studies

OBJECTIVE

So far, there have been no attempts to integrate the growing number of all brain volumetric magnetic resonance imaging studies in depression. In this comprehensive meta-analysis the magnitude and extent of brain volume differences between 2,418 patients with major depressive disorder and 1,974 healthy individuals from 64 studies was determined.

METHODS

A systematic research was conducted for volumetric magnetic resonance imaging studies of patients with major depressive disorder in relation to healthy control subjects. Studies had to report sufficient data for computation of effect sizes. For each study, the Cohen's d was calculated. All analyses were performed using the random effects model. Additionally, meta-regression analyses were done to explore the effects of potential sources of heterogeneity.

RESULTS

Patients showed large volume reductions in frontal regions, especially in the anterior cingulate and orbitofrontal cortex with smaller reductions in the prefrontal cortex. The hippocampus, the putamen and caudate nucleus showed moderate volume reductions.

CONCLUSIONS

This is the first comprehensive meta-analysis in major depressive disorder demonstrating structural brain abnormalities, particularly in those brain areas that are involved in emotion processing and stress-regulation.

Functional MRI study of memory-related brain regions in patients with depressive disorder

BACKGROUND

Structural imaging studies of patients suffering from depressive disorder have revealed reduced hippocampal volume in the majority of cases. The present study aimed specifically at investigating the hippocampal function in unipolar depression using functional magnetic resonance imaging (fMRI).

METHODS

Eleven unipolar depressed patients and eleven healthy control participants matched for age, gender and years of education underwent an associative learning paradigm during fMRI scanning. In the encoding condition of the paradigm, participants had to learn face-profession pairs. These pairs had to be remembered in the retrieval condition.

RESULTS

Hippocampal activity did not differ between depressive patients and control participants during encoding or retrieval. However, during encoding, depressive patients showed increased activity in the left parahippocampal gyrus and decreased activity in frontal and parietal regions. Retrieval of the associative pairs also yielded decreased activation patterns in depressive patients in frontal and parietal areas.

LIMITATIONS

The present findings may be limited by the small sample size of participants. Additionally the comparatively young age of the depressive sample could indicate a comparatively shorter duration of illness, and thereby less salient measurable hippocampal abnormalities.

CONCLUSION

The current study suggests that depression is associated with modified memory-related brain function. In particular the parahippocampal gyrus, the prefrontal cortex and parietal regions show functional alterations during associative learning. These structures as well as their interrelationships may play an important role in the pathogenesis of depressive disorder.

Clomipramine treatment reversed the glial pathology in a chronic unpredictable stress-induced rat model of depression

Growing evidence indicates that glia pathology contributes to the pathophysiology and possibly the etiology of depression. The study investigates changes in behaviors and glial fibrillary associated protein (GFAP) in the rat hippocampus after chronic unpredictable stress (CUS), a rat model of depression. Furthermore, we studied the effects of clomipramine, one of tricyclic antidepressants (TCAs), known to modulate serotonin and norepinephrine uptake, on CUS-induced depressive-like behaviors and GFAP levels. Rats exposed to CUS showed behavioral deficits in physical state, open field test and forced swimming test and exhibited a significant decrease in GFAP expression in the hippocampus. Interestingly, the behavioral and GFAP expression changes induced by CUS were reversed by chronic treatment with the antidepressant clomipramine. The beneficial effects of clomipramine treatment on CUS-induced depressive-like behavior and GFAP expression provide further validation of our hypothesis that glial dysfunction contributes to the pathophysiology of depression and that glial elements may represent viable targets for new antidepressant drug development.

Morphology of the corpus callosum in treatment-resistant schizophrenia and major depression

OBJECTIVE

To identify possible differences in the mean midsagittal corpus callosum (CC) total and subdivision areas in treatment-resistant schizophrenia and depression (TRS and TRD) patients.

METHOD

Areas of the total CC and its five equidistant subregions (from CC1 to CC5) obtained by parallel grid partitioning schemes were manually segmented from brain MRI of 42 TRS, 45 TRD patients and 30 healthy controls. The intracranial volume (ICV) normalized areas were calculated and compared between groups.

RESULTS

When compared with controls, patients with TRS had reduced ICV and a larger CC5, and TRD patients had a smaller CC4 while no significant difference in CC total area in patients with TRS or TRD was found. Multiple individual segments and total CC areas were significantly larger in TRS than TRD patients after normalization.

CONCLUSION

Patients with TRS and TRD have different CC morphological characteristics, and therefore there may be aberrant interhemispheric connectivity in schizophrenia and major depressive disorder patients.

Magnetization transfer imaging reveals the brain deficit in patients with treatment-refractory depression

BACKGROUND

Studies on treatment resistant depression (TRD) using advanced magnetic resonance imaging techniques are very limited.

METHODS

A group of 15 patients with clinically defined TRD and 15 matched healthy controls underwent magnetization transfer imaging (MTI) and T1-weighted (T1W) imaging. MTI data were processed and analyzed voxel-wised in SPM2. A voxel based morphometric (VBM) analysis was performed using T1W images.

RESULTS

Reduced magnetization transfer ratio was observed in the TRD group relative to normal controls in the anterior cingulate, insula, caudate tail and amygdala-parahippocampal areas. All these regions were identified within the right hemisphere. VBM revealed no morphological abnormalities in the TRD group compared to the control group. Negative correlations were found between MRI and clinical measures in the inferior temporal gyrus.

LIMITATIONS

The cross-sectional design and small sample size.

CONCLUSIONS

The findings suggest that MTI is capable of identifying subtle brain abnormalities which underlie TRD and in general more sensitive than morphological measures.

Ageing abolishes the effects of fluoxetine on neurogenesis

Depression constitutes a widespread condition observed in elderly patients. Recently, it was found that several drugs employed in therapies against depression stimulate hippocampal neurogenesis in young rodents and nonhuman primates. As the rate of neurogenesis is dramatically reduced during ageing, we examined the influences of ageing on neurogenic actions of antidepressants. We tested the impact of fluoxetine, a broadly used antidepressant, on hippocampal neurogenesis in mice of three different age groups (100, 200 and over 400 days of age). Proliferation and survival rate of newly generated cells, as well as the percentage of cells that acquired a neuronal phenotype were analyzed in the hippocampus of mice that received fluoxetine daily in a chronic manner. Surprisingly, the action of fluoxetine on neurogenesis was decreasing as a function of age and was only significant in young animals. Hence, fluoxetine increased survival and the frequency of neuronal marker expression in newly generated cells of the hippocampus in the young adult group (that is 100 days of age) only. No significant effects on neurogenesis could be detected in fluoxetine-treated adult and elderly mice (200 and over 400 days of age). The data indicate that the action of fluoxetine on neurogenesis is highly dependent on the age of the treated individual. Although the function of neurogenesis in the clinical manifestation of depression is currently a matter of speculation, this study clearly shows that the therapeutic effects of antidepressants in elderly patients are not mediated by neurogenesis modulation.

Prognostic and diagnostic potential of the structural neuroanatomy of depression

Background

Depression is experienced as a persistent low mood or anhedonia accompanied by behavioural and cognitive disturbances which impair day to day functioning. However, the diagnosis is largely based on self-reported symptoms, and there are no neurobiological markers to guide the choice of treatment. In the present study, we examined the prognostic and diagnostic potential of the structural neural correlates of depression.

Methodology and Principal Findings

Subjects were 37 patients with major depressive disorder (mean age 43.2 years), medication-free, in an acute depressive episode, and 37 healthy individuals. Following the MRI scan, 30 patients underwent treatment with the antidepressant medication fluoxetine or cognitive behavioural therapy (CBT). Of the patients who subsequently achieved clinical remission with antidepressant medication, the whole brain structural neuroanatomy predicted 88.9% of the clinical response, prior to the initiation of treatment (88.9% patients in clinical remission (sensitivity) and 88.9% patients with residual symptoms (specificity), p = 0.01). Accuracy of the structural neuroanatomy as a diagnostic marker though was 67.6% (64.9% patients (sensitivity) and 70.3% healthy individuals (specificity), p = 0.027).

Conclusions and Significance

The structural neuroanatomy of depression shows high predictive potential for clinical response to antidepressant medication, while its diagnostic potential is more limited. The present findings provide initial steps towards the development of neurobiological prognostic markers for depression.