Electroconvulsive therapy in melancholia: the role of hippocampal neurogenesis

Neurobiological mechanisms of electroconvulsive therapy for depression: Insights into hippocampal volumetric increases from clinical and preclinical studies

Depression is a highly prevalent and disabling psychiatric disorder. The hippocampus, which plays a central role in mood regulation and memory, has received considerable attention in depression research. Electroconvulsive therapy (ECT) is the most effective treatment for severe pharmacotherapy-resistant depression. Although the working mechanism of ECT remains unclear, recent magnetic resonance imaging (MRI) studies have consistently reported increased hippocampal volumes following ECT. The clinical implications of these volumetric increases and the specific cellular and molecular significance are not yet fully understood. This narrative review brings together evidence from animal models and human studies to provide a detailed examination of hippocampal volumetric increases following ECT. In particular, our preclinical MRI research using a mouse model is consistent with human findings, demonstrating a marked increase in hippocampal volume following ECT. Notable changes were observed in the ventral hippocampal CA1 region, including dendritic growth and increased synaptic density at excitatory synapses. Interestingly, inhibition of neurogenesis did not affect the ECT-related hippocampal volumetric increases detected on MRI. However, it remains unclear whether these histological and volumetric changes would be correlated with the clinical effect of ECT. Hence, future research on the relationships between cellular changes, ECT-related brain volumetric changes, and antidepressant effect could benefit from a bidirectional translational approach that integrates human and animal models. Such translational research may provide important insights into the mechanisms and potential biomarkers associated with ECT-induced hippocampal volumetric changes, thereby advancing our understanding of ECT for the treatment of depression.

What Can We Tell About the Effect of Electroconvulsive Therapy on the Human Hippocampus?

Electroconvulsive therapy (ECT) is the most effective antidepressant treatment, although its mechanisms of action remain unclear. Since 2010, several structural magnetic resonance imaging studies based on a neuroplastic hypothesis have consistently reported increases in the hippocampal volume following ECT. Moreover, volume increases in the human dentate gyrus, where neurogenesis occurs, have also been reported. These results are in line with the preclinical findings of ECT-induced neuroplastic changes, including neurogenesis, gliogenesis, synaptogenesis, and angiogenesis, in rodents and nonhuman primates. Despite this robust evidence of an effect of ECT on hippocampal plasticity, the clinical relevance of these human hippocampal changes continues to be questioned. This narrative review summarizes recent findings regarding ECT-induced hippocampal volume changes. Furthermore, this review also discusses methodological considerations and future directions in this field.

Serial electroconvulsive Seizure alters dendritic complexity and promotes cellular proliferation in the mouse dentate gyrus; a role for Egr3

BACKGROUND

Despite being one of the safest, most effective treatments for severe mood disorders, the therapeutic mechanisms of electroconvulsive therapy remain unknown. Electroconvulsive seizure (ECS) induces rapid, high-level expression of immediate early genes (IEGs) and brain-derived neurotrophic factor (BDNF), in addition to stimulation of neurogenesis and dendritic remodeling of dentate gyrus (DG) neurons. We have previously shown that this upregulation of BDNF fails to occur in the hippocampus of mice lacking the IEG Egr3. Since BDNF influences neurogenesis and dendritic remodeling, we hypothesized that Egr3-/- mice will exhibit deficits in neurogenesis and dendritic remodeling in response to ECS.

OBJECTIVE

To test this hypothesis, we examined dendritic remodeling and cellular proliferation in the DG of Egr3-/- and wild-type mice following repeated ECS.

METHODS

Mice received 10 daily ECSs. Dendritic morphology was examined in Golgi-Cox-stained tissue and cellular proliferation was analyzed through bromodeoxyuridine (BrdU) immunohistochemistry and confocal imaging.

RESULTS

Serial ECS in mice results in dendritic remodeling, increased spine density, and cellular proliferation in the DG. Loss of Egr3 alters the dendritic remodeling induced by serial ECS but does not change the number of dendritic spines or cellular proliferation consequences of ECS.

CONCLUSION

Egr3 influences the dendritic remodeling induced by ECS but is not required for ECS-induced proliferation of hippocampal DG cells.

Cerebral perfusion is related to antidepressant effect and cognitive side effects of Electroconvulsive Therapy

BACKGROUND

The mechanisms underlying the antidepressant effect and cognitive side effects of Electroconvulsive Therapy (ECT) remain elusive. The measurement of cerebral perfusion provides an insight into brain physiology.

OBJECTIVE

We investigated ECT-related perfusion changes in depressed patients and tested whether these changes correlate with clinical effects.

METHODS

A sample of 22 in-patients was examined at three time points: 1) within two days before, 2) within one week after, and 3) six months after an ECT series. Cerebral perfusion was quantified using arterial spin labeling magnetic resonance imaging. The primary regions of interest were the bilateral dorsolateral prefrontal cortices (DL-PFC) and hippocampi. The depression severity was assessed by the six-item Hamilton Depression Rating Scale, and cognitive performance by the Screen for Cognitive Impairment in Psychiatry. A linear mixed model and partial correlation were used for statistical analyses.

RESULTS

Following an ECT series, perfusion decreased in the right (-6.0%, p = .01) and left DL-PFC (-5.6%, p = .001). Perfusion increased in the left hippocampus (4.8%, p = .03), while on the right side the increase was insignificant (2.3%, p = .23). A larger perfusion reduction in the right DL-PFC correlated with a better antidepressant effect, and a larger perfusion increase in the right hippocampus with worse cognitive impairment.

CONCLUSION

ECT-induced attenuation of prefrontal activity may be related to clinical improvement, whereas a hippocampal process triggered by the treatment is likely associated with cognitive side effects.

Do increases in deep grey matter volumes after electroconvulsive therapy persist in patients with major depression? A longitudinal MRI-study

BACKGROUND

Previous MRI studies reported deep grey matter volume increases after electroconvulsive therapy (ECT) in patients with major depressive disorder (MDD). However, the clinical correlates of these changes are still unclear. It remains debated whether such volume changes are transient, and if they correlate with affective changes over time. We here investigated if ECT induces deep grey matter volume increases in MDD-patients; and, if so, whether volume changes persist over more than 9 months and whether they are related to the clinical outcome.

METHODS

We examined 16 MDD-patients with 3Tesla MRI before (baseline) and after an ECT-series and followed 12 of them up for 10-36 months. Patients' data were compared to 16 healthy controls. Affective scales were used to investigate the relationship between therapy-outcome and MRI changes.

RESULTS

At baseline, MDD-patients had lower values in global brain volume, white matter and peripheral grey matter compared to healthy controls, but we observed no significant differences in deep grey matter volumes. After ECT, the differences in peripheral grey matter disappeared, and patients demonstrated significant volume increases in the right hippocampus and both thalami, followed by subsequent decreases after 10-36 months, especially in ECT-responders. Controls did not show significant changes over time.

LIMITATIONS

Beside the relatively small, yet carefully characterized cohort, we address the variability in time between the third scanning session and the baseline.

CONCLUSIONS

ECT-induced deep grey matter volume increases are transient. Our results suggest that the thalamus might be a key region for the understanding of the mechanisms of ECT action.

Volume of hippocampal subregions and clinical improvement following electroconvulsive therapy in patients with depression

It is thought that the hippocampal neurogenesis is an important mediator of the antidepressant effect of electroconvulsive therapy (ECT). However, most previous studies failed to demonstrate the relationship between the increase in the hippocampal volume and the antidepressant effect. We reinvestigated this relationship by looking at distinct hippocampal subregions and applying repeated measures correlation. Using a 3 Tesla MRI-scanner, we scanned 22 severely depressed in-patients at three time points: before the ECT series, after the series, and at six-month follow-up. The depression severity was assessed by the 17-item Hamilton Rating Scale for Depression (HAMD-17). The hippocampus was segmented into subregions using Freesurfer software. The dentate gyrus (DG) was the primary region of interest (ROI), due to the role of this region in neurogenesis. The other major hippocampal subregions were the secondary ROIs (n = 20). The general linear mixed model and the repeated measures correlation were used for statistical analyses. Immediately after the ECT series, a significant volume increase was present in the right DG (Cohen's d = 1.7) and the left DG (Cohen's d = 1.5), as well as 15 out of 20 secondary ROIs. The clinical improvement, i.e., the decrease in HAMD-17 score, was correlated to the increase in the right DG volume (r_rm = -0.77, df = 20, p < .001), and the left DG volume (r_rm = -0.75, df = 20, p < .001). Similar correlations were observed in 14 out of 20 secondary ROIs. Thus, ECT induces an increase not only in the volume of the DG, but also in the volume of other major hippocampal subregions. The volumetric increases may reflect a neurobiological process that may be related to the ECT's antidepressant effect. Further investigation of the relationship between hippocampal subregions and the antidepressant effect is warranted. A statistical approach taking the repeated measurements into account should be preferred in the analyses.

Acute and long-term effects of electroconvulsive therapy on human dentate gyrus

Electroconvulsive therapy (ECT) is the most effective treatment for severe depression, although the underlying mechanisms remain unclear. Animal studies have consistently shown that electroconvulsive stimulation induces neuroplastic changes in the dentate gyrus. To date, few studies have investigated the effect of ECT on human hippocampal subfields. In the current study, structural magnetic resonance imaging (MRI) was conducted in 25 patients with major depressive episodes at 3 time points: before ECT (TP1), after 1 week of the last ECT (TP2) and after 3 months of the last ECT (TP3). Twenty healthy controls were scanned twice with an interval similar to patients between TP1 and TP2. Volumetric analyses of the cornu ammonis (CA)4/dentate gyrus (DG) were performed using the MAGeT-Brain (Multiple Automatically Generated Templates) algorithm. Clinically remitted patients after ECT showed larger volume increases in the right CA4/DG than non-remitted patients. Volume increases in the right CA4/DG were negatively associated with age. Increased CA4/DG volumes after ECT returned to baseline levels after 3 months irrespective of clinical state. ECT-induced volume increase in the CA4/DG was associated with age and clinical remission. These findings are consistent with the neurotrophic processes seen in preclinical studies. Neuroplastic change in the CA4/DG might mediate some of the short-term antidepressant effects of ECT.

Electroconvulsive therapy increases brain volume in major depression: a systematic review and meta-analysis

OBJECTIVE

The main purpose of this review was to synthesise evidence on ECT's effects on brain's structure.

METHOD

A systematic literature review of longitudinal studies of depressed patients treated with ECT using magnetic resonance imaging (MRI) and meta-analysis of ECT's effect on hippocampal volume.

RESULTS

Thirty-two studies with 467 patients and 285 controls were included. The MRI studies did not find any evidence of ECT-related brain damage. All but one of the newer MRI volumetric studies found ECT-induced volume increases in certain brain areas, most consistently in hippocampus. Meta-analysis of effect of ECT on hippocampal volume yielded pooled effect size: g = 0.39 (95% CI = 0.18-0.61) for the right hippocampus and g = 0.31 (95% CI = 0.09-0.53) for the left. The DTI studies point to an ECT-induced increase in the integrity of white matter pathways in the frontal and temporal lobes. The results of correlations between volume increases and treatment efficacy were inconsistent.

CONCLUSION

The MRI studies do not support the hypothesis that ECT causes brain damage; on the contrary, the treatment induces volume increases in fronto-limbic areas. Further studies should explore the relationship between these increases and treatment effect and cognitive side effects.

Effect of electroconvulsive therapy on neural response to affective pictures: A randomized, sham-controlled fMRI study

Electroconvulsive therapy (ECT) is the most effective treatment for severe depression but its neurocognitive mechanisms are unclear. This randomized, sham-controlled functional magnetic resonance imaging (fMRI) study explored the effects of a single ECT on neural response to affective pictures. Twenty-seven patients with major depressive disorder were randomized to a single active ECT (N = 15) or sham (N = 12) session in a double-blind, parallel-group design. On the following day, patients underwent fMRI during which they viewed pleasant, unpleasant and neutral pictures and performed a free recall test after the scan. Mood symptoms were assessed before ECT/sham and at the time of fMRI. Subsequently, all patients continued active ECT as usual. Mood symptoms were reassessed after six active ECT sessions. A single ECT vs. sham session reduced neural response to unpleasant vs. pleasant pictures in the medial prefrontal cortex, a region showing greater response in the more depressed patients. This effect occurred in the absence of between-group differences in picture recall, mood symptoms or concomitant medication. In conclusion, modulation of medial prefrontal hyper-activity during encoding of negative affective information may be a common mechanism of distinct biological depression treatments.

Electroconvulsive therapy enhances the anti-ageing hormone Klotho in the cerebrospinal fluid of geriatric patients with major depression

Klotho is a humoral factor with pleiotropic effects. Most notably, Klotho deficiency is associated with a phenotype comprising organ manifestations accompanying aging including atherosclerosis and cognitive impairment. Research on the role of Klotho in affective disorder is scarce, which is surprising in light of the fact that depression is associated with accelerated cellular aging as well as aging-related phenotypes and comorbidity observed in Klotho deficiency. On these grounds we investigated Klotho levels in the cerebrospinal fluid (CSF) and serum of eight geriatric patients undergoing electroconvulsive therapy (ECT) for severe depression. We hypothesize that ECT as a highly effective antidepressant treatment leads enhances Klotho levels. We found a significant difference between pre- and post-ECT CSF Klotho (792.5pg/ml vs. 991.3pg/ml, p=0.0020), but no difference in serum Klotho (602.5 vs. 594.3, p=0.32). Moreover, CSF Klotho increase positively correlated with the number of single ECT sessions that were performed in each patient (F1, 6)=7.84, p=0.031). Conjointly, the results of our exploratory study with a small sample size suggest a central nervous system-specific impact of ECT on Klotho, which may in turn partake in mediating the antidepressant effect of ECT. We suggest the modulation of neuroinflammatory processes, which have been ascribed pathophysiological relevance within the conceptual framework of the neuroinflammation hypothesis of depression, through ECT as a potential mechanism by which Klotho is enhanced in response to treatment. Further preclinical and clinical investigation should aim for a precise identification of the role of Klotho in depressive disorder.

Neural Response After a Single ECT Session During Retrieval of Emotional Self-Referent Words in Depression: A Randomized, Sham-Controlled fMRI Study

BACKGROUND

Negative neurocognitive bias is a core feature of depression that is reversed by antidepressant drug treatment. However, it is unclear whether modulation of neurocognitive bias is a common mechanism of distinct biological treatments. This randomized controlled functional magnetic resonance imaging study explored the effects of a single electroconvulsive therapy session on self-referent emotional processing.

METHODS

Twenty-nine patients with treatment-resistant major depressive disorder were randomized to one active or sham electroconvulsive therapy session at the beginning of their electroconvulsive therapy course in a double-blind, between-groups design. The following day, patients were given a self-referential emotional word categorization test and a free recall test. This was followed by an incidental word recognition task during whole-brain functional magnetic resonance imaging at 3T. Mood was assessed at baseline, on the functional magnetic resonance imaging day, and after 6 electroconvulsive therapy sessions. Data were complete and analyzed for 25 patients (electroconvulsive therapy: n = 14, sham: n = 11). The functional magnetic resonance imaging data were analyzed using the FMRIB Software Library randomize algorithm, and the Threshold-Free Cluster Enhancement method was used to identify significant clusters (corrected at P < .05).

RESULTS

A single electroconvulsive therapy session had no effect on hippocampal activity during retrieval of emotional words. However, electroconvulsive therapy reduced the retrieval-specific neural response for positive words in the left frontopolar cortex. This effect occurred in the absence of differences between groups in behavioral performance or mood symptoms.

CONCLUSIONS

The observed effect of electroconvulsive therapy on prefrontal response may reflect early facilitation of memory for positive self-referent information, which could contribute to improvements in depressive symptoms including feelings of self-worth with repeated treatments.

Does a single session of electroconvulsive therapy alter the neural response to emotional faces in depression? A randomised sham-controlled functional magnetic resonance imaging study

Negative neurocognitive bias is a core feature of major depressive disorder that is reversed by pharmacological and psychological treatments. This double-blind functional magnetic resonance imaging study investigated for the first time whether electroconvulsive therapy modulates negative neurocognitive bias in major depressive disorder. Patients with major depressive disorder were randomised to one active ( n=15) or sham electroconvulsive therapy ( n=12). The following day they underwent whole-brain functional magnetic resonance imaging at 3T while viewing emotional faces and performed facial expression recognition and dot-probe tasks. A single electroconvulsive therapy session had no effect on amygdala response to emotional faces. Whole-brain analysis revealed no effects of electroconvulsive therapy versus sham therapy after family-wise error correction at the cluster level, using a cluster-forming threshold of Z>3.1 ( p<0.001) to secure family-wise error <5%. Groups showed no differences in behavioural measures, mood and medication. Exploratory cluster-corrected whole-brain analysis ( Z>2.3; p<0.01) revealed electroconvulsive therapy-induced changes in parahippocampal and superior frontal responses to fearful versus happy faces as well as in fear-specific functional connectivity between amygdala and occipito-temporal regions. Across all patients, greater fear-specific amygdala - occipital coupling correlated with lower fear vigilance. Despite no statistically significant shift in neural response to faces after a single electroconvulsive therapy session, the observed trend changes after a single electroconvulsive therapy session point to an early shift in emotional processing that may contribute to antidepressant effects of electroconvulsive therapy.

Hippocampal volume changes following electroconvulsive therapy: a systematic review and meta-analysis

INTRODUCTION

Reduced hippocampal volume is one of the most consistent morphological findings in Major Depressive Disorder (MDD). Electroconvulsive therapy (ECT) is the most effective therapy for MDD, yet its mechanism of action remains poorly understood. Animal models show that ECT induces several neuroplastic processes, which lead to hippocampal volume increases. We conducted a meta-analysis of ECT studies in humans to investigate its effects on hippocampal volume.

METHODS

PubMed was searched for studies examining hippocampal volume before and after ECT. A random-effects model was used for meta-analysis with standardized mean difference (SMD) of the change in hippocampal volume before and after ECT as the primary outcome. Nine studies involving 174 participants were included.

RESULTS

Total hippocampal volumes increased significantly following ECT compared to pre-treatment values (SMD=1.10; 95% CI 0.80-1.39; z=7.34; p<0.001; k=9). Both right (SMD=1.01; 95% CI 0.72-1.30; z=6.76; p<0.001; k=7) and left (SMD=0.87; 95% CI 0.51-1.23; z=4.69; p<0.001; k=7) hippocampal volumes were also similarly increased significantly following ECT. We demonstrated no correlation between improvement in depression symptoms with ECT and change in total hippocampal volume (beta=-1.28, 95% CI -4.51-1.95, z=-0.78, p=0.44).

CONCLUSION

We demonstrate fairly consistent increases in hippocampal volume bilaterally following ECT treatment. The relationship among these volumetric changes and clinical improvement and cognitive side effects of ECT should be explored by larger, multisite studies with harmonized imaging methods.

Electroconvulsive Therapy-Induced Brain Structural and Functional Changes in Major Depressive Disorders: A Longitudinal Study

Background

This study aimed to study the brain structural and functional changes after 8 courses of electroconvulsive therapy (ECT) on patients with major depressive disorder (MDD).

Material/Methods

MRI scans were performed on 12 depressive patients before and after 8 courses of ECT and compared with those of 15 normal controls. Data were analyzed by voxel-based morphometry (VBM) using SPM8 software. Functional MRI (fMRI) and regional homogeneity (ReHo) analyses were used to assess the functional changes after ECT.

Results

Grey matter volumes were smaller in the right cingulate gyrus of depressive patients before ECT compared with normal controls. After false discovery rate (FDR) correction, post-ECT grey matter volumes were increased in bilateral amygdala and hippocampus compared with pre-ECT. Resting-state ReHo maps showed significant differences in brain activity pre- and post-ECT. Compared with healthy controls, MDD patients treated with 8 courses of ECT showed higher ReHo values in the bilateral frontal lobe, bilateral parietal lobe, and right caudate nucleus. Decreased ReHo values were observed in the right medial temporal gyrus, right superior temporal gyrus, right cingulate gyrus, and left anterior cerebellar lobe.

Conclusions

Results suggested that there were both structural and functional differences between the brains of MDD patients and healthy controls. After ECT, both structural and functional changes occurred, but without complete recovery to normal. ECT may display effects through regulating other brain regions to compensate for the original defects.

The utility of a classificatory decision tree approach to assist clinical differentiation of melancholic and non-melancholic depression

BACKGROUND

Studies suggest that differentiating melancholic from non-melancholic depressive disorders is advanced by use of illness course as well as symptom variables but, in practice, potentially differentiating variables are generally positioned as having equal value. Judging that differentiating features are more likely to vary in their signal intensity, we sought to determine the number of features required to effect differentiation and their hierarchical order.

METHODS

The 24-item clinician-rated Sydney Melancholia Prototype Index (SMPI-CR) was completed for 364 unipolar depressed patients. The sample was divided into two cohorts according to the recruitment period. An RPART classification tree analysis identified the most discriminating SMPI items in the development sample of 197 patients, and examined the sensitivity and specificity of the diagnostic decisions, then sought to replicate findings in a validation sample of 169 patients.

RESULTS

Independent analyses of putative SMPI items identified only seven items as required to discriminate those with clinically-diagnosed melancholic or non-melancholic depression when the conditions were examined separately. An RPART analysis considering differentiation of melancholic and non-melancholic depression in the total samples retained five of those items in the classification tree, three of which were non-symptom items, and with 92% sensitivity and 80% specificity in the development sample. This reduced item set showed 93% sensitivity and 82% specificity in the validation sample.

LIMITATIONS

Our clinical judgment of melancholic or non-melancholic depression may not correspond with the clinical logic employed by other clinicians.

CONCLUSION

Only five SMPI items were required to derive a succinct and efficient decision tree, comprising high sensitivity and specificity in differentiating melancholic and non-melancholic depression. Current study findings provide an empirical model that could enrich clinicians׳ approach to differentiating melancholic and non-melancholic depression.

Antidepressant-like Effects of Electroconvulsive Seizures Require Adult Neurogenesis in a Neuroendocrine Model of Depression

BACKGROUND

Neurogenesis continues throughout life in the hippocampal dentate gyrus. Chronic treatment with monoaminergic antidepressant drugs stimulates hippocampal neurogenesis, and new neurons are required for some antidepressant-like behaviors. Electroconvulsive seizures (ECS), a laboratory model of electroconvulsive therapy (ECT), robustly stimulate hippocampal neurogenesis.

HYPOTHESIS

ECS requires newborn neurons to improve behavioral deficits in a mouse neuroendocrine model of depression.

METHODS

We utilized immunohistochemistry for doublecortin (DCX), a marker of migrating neuroblasts, to assess the impact of Sham or ECS treatments (1 treatment per day, 7 treatments over 15 days) on hippocampal neurogenesis in animals receiving 6 weeks of either vehicle or chronic corticosterone (CORT) treatment in the drinking water. We conducted tests of anxiety- and depressive-like behavior to investigate the ability of ECS to reverse CORT-induced behavioral deficits. We also determined whether adult neurons are required for the effects of ECS. For these studies we utilized a pharmacogenetic model (hGFAPtk) to conditionally ablate adult born neurons. We then evaluated behavioral indices of depression after Sham or ECS treatments in CORT-treated wild-type animals and CORT-treated animals lacking neurogenesis.

RESULTS

ECS is able to rescue CORT-induced behavioral deficits in indices of anxiety- and depressive-like behavior. ECS increases both the number and dendritic complexity of adult-born migrating neuroblasts. The ability of ECS to promote antidepressant-like behavior is blocked in mice lacking adult neurogenesis.

CONCLUSION

ECS ameliorates a number of anxiety- and depressive-like behaviors caused by chronic exposure to CORT. ECS requires intact hippocampal neurogenesis for its efficacy in these behavioral indices.

Hippocampal volume in relation to clinical and cognitive outcome after electroconvulsive therapy in depression

OBJECTIVE

In a previous magnetic resonance imaging (MRI) study, we found a significant increase in hippocampal volume immediately after electroconvulsive therapy (ECT) in patients with depression. The aim of this study was to evaluate hippocampal volume up to 1 year after ECT and investigate its possible relation to clinical and cognitive outcome.

METHOD

Clinical and cognitive outcome in 12 in-patients with depression receiving antidepressive pharmacological treatment referred for ECT were investigated with the Montgomery-Asberg Depression Rating Scale (MADRS) and a broad neuropsychological test battery within 1 week before and after ECT. The assessments were repeated 6 and 12 months after baseline in 10 and seven of these patients, respectively. Hippocampal volumes were measured on all four occasions with 3 Tesla MRI.

RESULTS

Hippocampal volume returned to baseline during the follow-up period of 6 months. Neither the significant antidepressant effect nor the significant transient decrease in executive and verbal episodic memory tests after ECT could be related to changes in hippocampal volume. No persistent cognitive side effects were observed 1 year after ECT.

CONCLUSION

The immediate increase in hippocampal volume after ECT is reversible and is not related to clinical or cognitive outcome.

Clinical patterns and treatment outcome in patients with melancholic, atypical and non-melancholic depressions

OBJECTIVE

To assess sociodemographic, clinical and treatment factors as well as depression outcome in a large representative clinical sample of psychiatric depressive outpatients and to determine if melancholic and atypical depression can be differentiated from residual non-melancholic depressive conditions.

SUBJECTS/MATERIALS AND METHOD

A prospective, naturalistic, multicentre, nationwide epidemiological study of 1455 depressive outpatients was undertaken. Severity of depressive symptoms was assessed by the Hamilton Depression Rating Scale (HDRS) and the Self Rated Inventory of Depressive Symptomatology (IDS-SR(30)). IDS-SR(30) defines melancholic and atypical depression according to DSM-IV criteria. Assessments were carried out after 6-8 weeks of antidepressant treatment and after 14-20 weeks of continuation treatment.

RESULTS

Melancholic patients (16.2%) were more severely depressed, had more depressive episodes and shorter episode duration than atypical (24.7%) and non-melancholic patients. Atypical depressive patients showed higher rates of co-morbid anxiety disorders and substance abuse. Melancholic patients showed lower rates of remission.

CONCLUSION

Our study supports a different clinical pattern and treatment outcome for melancholic and atypical depression subtypes.

Roles of NG2 glial cells in diseases of the central nervous system

NG2 cells are a novel distinct class of central nervous system (CNS) glial cells, characterized by the expression of the chondroitin sulfate proteoglycan NG2. They have been detected in a variety of human CNS diseases. As morphological, physiological and biomolecular studies of NG2 cells have been conducted, their roles have been gradually revealed. Research on cellular and molecular mechanisms in the pathophysiological state was built on the preliminary findings of their physiological functions; and in turn, this helps to clarify their physiological roles and leads to the identification of novel therapeutic targets. This review summarizes recent findings regarding the potential roles of NG2 cells in traumatic brain injury, multiple sclerosis, glioma, epilepsy, Alzheimer's disease and electroconvulsive therapy for depression.

Activation of latent precursors in the hippocampus is dependent on long-term potentiation

The recent discovery of a large latent population of precursor cells in the dentate gyrus of adult mice led us to investigate whether activation of this population is regulated by synaptic activity, thereby explaining the observation that environmental signals can affect neurogenesis. Using a variety of stimulation protocols, we found that only a long-term potentiation (LTP)-inducing protocol activated the latent precursor pool, leading to increased neurogenesis in the dentate gyrus. LTP induced by high-frequency stimulation (HFS) of the perforant pathway in vivo produced a two-fold increase in the number of neurospheres cultured from the stimulated hippocampus, compared with the unstimulated hippocampus. No increase in neurosphere number or neurogenesis was observed when the HFS failed to induce LTP. These results show that LTP can activate latent neural precursor cells in the adult mouse dentate gyrus, thereby providing a direct mechanism for regulating activity-driven neurogenesis. In the future, it may be possible to utilize such learning- or stimulation-induced neurogenesis to overcome disorders characterized by neuronal loss.

How does electroconvulsive therapy work? Theories on its mechanism

This article reviews 3 current theories of electroconvulsive therapy (ECT). One theory points to generalized seizures as essential for the therapeutic efficacy of ECT. Another theory highlights the normalization of neuroendocrine dysfunction in melancholic depression as a result of ECT. A third theory is based on recent findings of increased hippocampal neurogenesis and synaptogenesis in experimental animals given electroconvulsive seizures. Presently, the endocrine theory has the strongest foundation to explain the working mechanism of ECT.

Regulation of the galanin system by repeated electroconvulsive seizures in mice

Even though induction of seizures by electroconvulsive stimulation (ECS) is a treatment widely used for major depression in humans, the working mechanism of ECS remains uncertain. The antiepileptic effect of ECS has been suggested to be involved in mediating the therapeutic effect of ECS. The neuropeptide galanin exerts antiepileptic and antidepressant-like effects and has also been implicated in the pathophysiology of depression. To explore a potential role of galanin in working mechanisms of ECS, the present study examined effects of repeated ECS on the galanin system using QRT-PCR, in situ hybridization, and [(125) I]galanin receptor binding. ECS was administered to adult mice daily for 14 days, and this paradigm was confirmed to exert antidepressant-like effect in the tail suspension test. Prominent increases in galanin gene expression were found in several brain regions involved in regulation of epileptic activity and depression, including the piriform cortex, hippocampal dentate gyrus, and amygdala. Likewise, GalR2 gene expression was up-regulated in both the central and the medial amygdala, whereas GalR1 gene expression showed a modest down-regulation in the medial amygdala. [(125) I]galanin receptor binding in the piriform cortex, hippocampus, and amygdala was found to be significantly down-regulated. These data show that the galanin system is regulated by repeated ECS in a number of brain regions implicated in seizure regulation and depression. These changes may play a role in the therapeutic effect of ECS.

Electroconvulsive therapy: Part I. A perspective on the evolution and current practice of ECT

The concept of inducing convulsions, mainly through chemical means, to promote mental wellness has existed since the 16th century. In 1938, Italian scientists first applied electrically induced therapeutic seizures. Although electroconvulsive therapy (ECT) is employed in the treatment of several psychiatric disorders, it is most frequently used today to treat severe depressive episodes and remains the most effective treatment available for those disorders. Despite this, ECT continues to be the most stigmatized treatment available in psychiatry, resulting in restrictions on and reduced accessibility to a helpful and potentially life-saving treatment. The psychiatric and psychosocial ramifications of this stigmatization may include the exacerbation of the increasingly serious, global health problem of major depressive disorders as well as serious consequences for individual patients who may not be offered, or may refuse, a potentially beneficial treatment. The goal of this first article in this two-part series is to provide an overview of ECT's historical development and discuss the current state of knowledge about ECT, including technical aspects of delivery, patient selection, its side-effect profile, and factors that may contribute to underuse of ECT.

Effects of different antidepressant treatments on the core of depression

Core symptoms of depression are a combination of psychological and somatic symptoms, often combined with psychomotor and cognitive disturbances. Diagnostic classification of depression including the concepts of melancholic, endogenous, or severe depression describe severely depressed patients suffering from most of the core symptoms, together with clinical characteristics of a cyclic unipolar or bipolar course, lower placebo response rates, higher response rates to electroconvulsive therapy, to antidepressant treatments with dually or mixed modes of action, or to lithium augmentation. Higher rates ofhypothalamic-pituitary-adrenal axis hyperactivity and specific electroencephalograph patterns have also been shown in this patient group. Summarizing the symptomatology of depression in these patients, a broad overlap between the abovementioned subgroups can be suggested. Because the positive diagnosis of those core symptoms of depression may include clinical consequences, it would be of use to integrate all the mentioned concepts in the upcoming new versions of the diagnostic systems DSM-V and ICD-11.

Individualized continuation electroconvulsive therapy and medication as a bridge to relapse prevention after an index course of electroconvulsive therapy in severe mood disorders: a naturalistic 3-year cohort study

Electroconvulsive therapy (ECT) is recognized as an effective acute treatment for mood disorders but is associated with high risk of relapse. To minimize this risk, we introduced as a routine individually tapered continuation ECT with concomitant medication (C-ECT + Med) after an index series in January 2000. In August 2002, a chart review of all patients (n = 41) who had received C-ECT + Med for more than 4 months was carried out. Sixteen patients also participated in an extensive interview. Mean duration of administered C-ECT at follow-up was 1 year, but for most patients (63%), C-ECT had been terminated. For 49% of patients, adjustments between ECT sessions had been made due to early signs of relapse. Two weeks was the most common interval between sessions for patients with ongoing C-ECT. The frequency of lithium-treated patients had increased from 12% before index to 41% during C-ECT. However, the rated response to the drug varied. Need for hospital care 3 years before and after the initiation of C-ECT + Med was compared in a second evaluation of the cohort. The number of patients hospitalized, number of admissions, and total days in hospital were all significantly reduced. Hospital days were reduced by 76% (P < 0.001). Three patients with previously cumulative years in hospital are described as case vignettes after 6 years with no or minimal need for further hospitalization. This study supports previous findings that individually tapered C-ECT + Med can maintain initial response to ECT and serve as a bridge to long-term relapse prevention.

Neurobiological correlates of the cognitive side effects of electroconvulsive therapy

Although electroconvulsive therapy (ECT) is a highly effective form of treatment, its use is limited by the emergence of cognitive side effects, notably anterograde and retrograde amnesia. Despite a large literature on the neurobiology of therapeutic mechanisms of ECT, very little is known about the neurobiological underpinnings of its cognitive effects. On theoretical grounds, structures within the medial temporal lobes, especially the hippocampus, are predicted to be critical regions mediating anterograde and, possibly, retrograde amnesia. However, functional neuroimaging studies in normal volunteers have demonstrated that frontal cortical regions are also involved in human memory processes. This review will highlight some of the biochemical, electrophysiological, and neuroimaging correlates of the amnestic side effects of ECT. In terms of electrophysiological and functional imaging studies, there are data that implicate both medial temporal and frontal regions as being associated with cognitive dysfunction. Interestingly, such data also appear to indicate a dissociation of the neural systems critical to the efficacy and adverse cognitive effects of ECT.

Neurobiology of bipolar disorder

Bipolar disorder is one of the most severely debilitating of all medical illnesses. It can lead to significant suffering for patients and their families, limit functioning and workplace productivity, and with its risks of increased morbidity and mortality, it is increasingly recognized as a major public health problem. For a large number of patients, outcomes are poor. Patients with bipolar disorder generally experience high rates of relapse, a chronic recurrent course, lingering residual symptoms, functional impairment, psychosocial disability and diminished well-being. Despite this, little is known about the specific pathophysiology of bipolar disorder. A better understanding of the neurobiological underpinnings of this condition, informed by preclinical and clinical research, will be essential for the future development of specific targeted therapies that are more effective, achieve their effects more quickly and are better tolerated than currently available treatments. An abundance of research has implicated specific neuroendocrine, neurotransmitter and intracellular signaling systems in the pathophysiology and treatment of this illness. More recently, genetic association studies have identified numerous genes that confer vulnerability to the disorder, many of which are known to function in the signaling pathways previously identified as relevant to the etiology of the illness. In this article, we will review current knowledge regarding the neurotransmitter systems, signaling networks, neuroendocrine systems and genetics of bipolar disorder; all of these allow insight into the mechanism of illness and thus offer potential novel directions for the development of novel therapeutics.