Structural neuroimaging studies in late-life depression: a review

P, Gupta C. Correlation of age with the size of subcortical nuclei of the brain and its implication in degenerative disease: A magnetic resonance imaging study

Background

Aging is a non-modifiable risk factor for neurodegenerative disease. It is well established that the brain undergoes physiological atrophy with age. So, this study was conducted to analyse the correlation between the age of the person and the size of the various subcortical nuclei of the brain and whether these measurements can serve as a useful indicator for physiological atrophy leading to degenerative disease in clinical practice.

Methods

A total of 600 MRI scans from healthy individuals were examined and the measurements of subcortical nuclei were taken and subsequently analysed.

Results

A statistically significant difference between the genders was observed in the sizes of the axial diameters of caudate nucleus, putamen and globus pallidus. Caudate nucleus transverse diameter showed a moderate negative correlation with age in males. Globus pallidus axial diameter with age showed weak positive correlation for males. Globus pallidus transverse diameter showed weak positive correlation with age for both males and females, but it was stronger for males compared to females.

Conclusions

These results will help neurologists and neurosurgeons in analysing various early degenerative diseases and treat them accordingly.

Challenges in Identifying Individualized Brain Biomarkers of Late Life Depression

Research into neuroimaging biomarkers for Late Life Depression (LLD) has identified neural correlates of LLD including increased white matter hyperintensities and reduced hippocampal volume. However, studies into neuroimaging biomarkers for LLD largely fail to converge. This lack of replicability is potentially due to challenges linked to construct variability, etiological heterogeneity, and experimental rigor. We discuss suggestions to help address these challenges, including improved construct standardization, increased sample sizes, multimodal approaches to parse heterogeneity, and the use of individualized analytical models.

Associations of lesion location, structural disconnection, and functional diaschisis with depressive symptoms post stroke

Introduction

Post-stroke depressive symptoms (PSDS) are common and relevant for patient outcome, but their complex pathophysiology is ill understood. It likely involves social, psychological and biological factors. Lesion location is a readily available information in stroke patients, but it is unclear if the neurobiological substrates of PSDS are spatially localized. Building on previous analyses, we sought to determine if PSDS are associated with specific lesion locations, structural disconnection and/or localized functional diaschisis.

Methods

In a prospective observational study, we examined 270 patients with first-ever stroke with the Hospital Anxiety and Depression Scale (HADS) around 6 months post-stroke. Based on individual lesion locations and the depression subscale of the HADS we performed support vector regression lesion-symptom mapping, structural-disconnection-symptom mapping and functional lesion network-symptom-mapping, in a reanalysis of this previously published cohort to infer structure-function relationships.

Results

We found that depressive symptoms were associated with (i) lesions in the right insula, right putamen, inferior frontal gyrus and right amygdala and (ii) structural disconnection in the right temporal lobe. In contrast, we found no association with localized functional diaschisis. In addition, we were unable to confirm a previously described association between depressive symptom load and a network damage score derived from functional disconnection maps.

Discussion

Based on our results, and other recent lesion studies, we see growing evidence for a prominent role of right frontostriatal brain circuits in PSDS.

The heterogeneity of late-life depression and its pathobiology: a brain network dysfunction disorder

Depression is frequent in older individuals and is often associated with cognitive impairment and increasing risk of subsequent dementia. Late-life depression (LLD) has a negative impact on quality of life, yet the underlying pathobiology is still poorly understood. It is characterized by considerable heterogeneity in clinical manifestation, genetics, brain morphology, and function. Although its diagnosis is based on standard criteria, due to overlap with other age-related pathologies, the relationship between depression and dementia and the relevant structural and functional cerebral lesions are still controversial. LLD has been related to a variety of pathogenic mechanisms associated with the underlying age-related neurodegenerative and cerebrovascular processes. In addition to biochemical abnormalities, involving serotonergic and GABAergic systems, widespread disturbances of cortico-limbic, cortico-subcortical, and other essential brain networks, with disruption in the topological organization of mood- and cognition-related or other global connections are involved. Most recent lesion mapping has identified an altered network architecture with "depressive circuits" and "resilience tracts", thus confirming that depression is a brain network dysfunction disorder. Further pathogenic mechanisms including neuroinflammation, neuroimmune dysregulation, oxidative stress, neurotrophic and other pathogenic factors, such as β-amyloid (and tau) deposition are in discussion. Antidepressant therapies induce various changes in brain structure and function. Better insights into the complex pathobiology of LLD and new biomarkers will allow earlier and better diagnosis of this frequent and disabling psychopathological disorder, and further elucidation of its complex pathobiological basis is warranted in order to provide better prevention and treatment of depression in older individuals.

The impact of depression on language function in individuals with Alzheimer's disease: a pre/post-treatment design

BACKGROUND

It is uncertain whether depression might affect cognitive function in Alzheimer's disease (AD). Most of studies on the effect of depression treatment on cognitive function in AD were briefly evaluated by Mini-Mental State Examination (MMSE). MMSE is poor sensitive to detect cognitive change. This study examined the cognitive response to depression treatment in AD via multi-domain assessment. In addition, we explored whether effect of depression treatment in AD is different those of late-life depression (LLD).

METHODS

This study include AD patients with depression (AD + D) and without depression (AD - D), LLD patients (LLD), and healthy controls (HC). The patients were treated according to their diagnosis for 16 weeks: acetylcholinesterase inhibitors (AChEIs) and selective serotonin reuptake inhibitors (SSRIs) for AD + D, AChEIs for AD - D, and SSRIs for LLD. The cognitive changes from pre- to post-treatment were compared between AD + D and AD - D or LLD and HC. An independent sample t test was performed to compare the degree of change between the groups. Paired t tests were used to determine cognitive function changes in each depression treatment responder group.

RESULTS

At baseline, AD + D had more impairment in language function compared to AD - D, and LLD had greater deficit in executive function than HC. After depression treatment, more impaired cognitive domains at baseline were improved in AD + D and LLD, respectively. Moreover, AD + D showed an improvement in the global cognitive function (MMSE).

CONCLUSIONS

Results indicated that language function was influenced by depression in AD, which is first evidence for specific cognitive domain related to depression in AD. Our finding indicates that depression could negatively impact cognitive function, and depression treatment may have beneficial cognitive effect in both AD and LLD. This study suggests the importance of early detection and treatment of depression in AD and LLD. Trial registration Clinical Research Information Service, CRIS, ID#: KCT0004041, Registered 5 June 2019, retrospectively registered after first patient enrollment date (4 March 2014) https://cris.nih.go.kr/cris/search/detailSearch.do?seq=14140&status=5&seq_group=14140&search_page=M .

The Laterality of Age-Related Hearing Loss and Depression

OBJECTIVE

There is a known association between hearing loss (HL) and depressive symptoms. The objective was to establish if there is a stronger association with the left or right ear.

STUDY DESIGN

Cross-sectional analysis of an ongoing prospective epidemiologic cohort study.

SETTING

Hispanic Community Health Study (US, multicentered).

PATIENTS

Five thousand three hundred and twenty-eight adults 2:50 years old.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

The main outcome was depressive symptoms, measured by the 10-Item Center for Epidemiologic Studies Depression Scale-10 (CESD-10) and defined continuously and binarily. Subjects with CESD-10 2: 10 were categorized as having clinically significant depressive symptoms (CSDS). Linear and logistic regressions were performed to assess the association between depressive symptoms and hearing in each ear, controlling for hearing aid use, age, sex, educational level, study site, geographic background, cardiovascular disease, and antidepressant use.

RESULTS

Mean age was 58.5 ± 6.3 years. Mean pure-tone average (PTA) was 20.3 ± 11.7 dB (range = 0 - 125) in the right ear and 20.3 ± 12.4 dB (range = -2.5 to 120) in the left. Multivariable regression adjusting for covariates demonstrated significant associations between depressive symptoms and HL in both the left and right ear. For every 20-dB worsening in right ear PTA, there was 0.89-point increase in CESD-10 (95% confidence interval = 0.59 - 1.2), and odds of CSDS increased 1.31 times (1.17 - 1.46). For every 20-dB worsening in left ear PTA, there was a 0.85-point increase in CESD-10 (0.55 - 1.14), and odds of CSDS increased 1.34 times (1.20 - 1.49).

CONCLUSIONS

Worsening hearing in the right and left ears individually was associated with increased depressive symptoms and odds of CSDS. No ear laterality was demonstrated.

Multiple Aspects of Inappropriate Action of Renin-Angiotensin, Vasopressin, and Oxytocin Systems in Neuropsychiatric and Neurodegenerative Diseases

The cardiovascular system and the central nervous system (CNS) closely cooperate in the regulation of primary vital functions. The autonomic nervous system and several compounds known as cardiovascular factors, especially those targeting the renin-angiotensin system (RAS), the vasopressin system (VPS), and the oxytocin system (OTS), are also efficient modulators of several other processes in the CNS. The components of the RAS, VPS, and OTS, regulating pain, emotions, learning, memory, and other cognitive processes, are present in the neurons, glial cells, and blood vessels of the CNS. Increasing evidence shows that the combined function of the RAS, VPS, and OTS is altered in neuropsychiatric/neurodegenerative diseases, and in particular in patients with depression, Alzheimer's disease, Parkinson's disease, autism, and schizophrenia. The altered function of the RAS may also contribute to CNS disorders in COVID-19. In this review, we present evidence that there are multiple causes for altered combined function of the RAS, VPS, and OTS in psychiatric and neurodegenerative disorders, such as genetic predispositions and the engagement of the RAS, VAS, and OTS in the processes underlying emotions, memory, and cognition. The neuroactive pharmaceuticals interfering with the synthesis or the action of angiotensins, vasopressin, and oxytocin can improve or worsen the effectiveness of treatment for neuropsychiatric/neurodegenerative diseases. Better knowledge of the multiple actions of the RAS, VPS, and OTS may facilitate programming the most efficient treatment for patients suffering from the comorbidity of neuropsychiatric/neurodegenerative and cardiovascular diseases.

Different Sides of Depression in the Elderly: An In-depth View on the Role of Aβ Peptides

BACKGROUND

Late-onset depression (LOD) is the most common neuropsychiatric disorder associated with Alzheimer's disease (AD), often associated with structural and functional brain changes, neuropsychological impairments and negative family history for affective disorders. LOD could be a risk factor or a prodromal phase of AD; this has led to the investigation of the link between depression and amyloid-β (Aβ) peptides by measuring Aβ levels in plasma, cerebrospinal fluid (CSF) and brains of elderly depressed subjects.

OBJECTIVE

Clarify the complex relationship between depression, Aβ peptides and AD.

METHOD

We evaluated all articles published up to 2019 in PubMed in which Aβ was measured in serum (or plasma), CSF or brain in elderly with Major Depressive Disorder or depressive symptoms evaluated with standard scales.

RESULTS

Low plasma Aβ42 levels are strongly associated with depression severity. Plasma Aβ40 levels are higher in younger depressed, drug-resistant and those with more severe symptoms. CSF Aβ42 levels are lower in depressed than controls. PET-detected global and region-specific increases in Aβ deposition are sometimes associated with LOD, cognitive impairment, anxiety but not with Cardiovascular Diseases (CVDs)/CVD risk factors. Elderly depressed with CVDs/CVD risk factors have more frequently high plasma Aβ40 levels and drug-resistance; those without these co-morbidities have low plasma Aβ42 levels and a greater cognitive impairment.

CONCLUSION

Two specific Aβ profiles emerge in elderly depressed. One is associated with Aβ42 reductions in plasma and CSF, possibly reflecting increased brain amyloid deposition and prodromal AD. The other one is characterized by high plasma Aβ40 levels, cerebrovascular disease and clinically associated with increased AD risk.

Magnetic resonance imaging in mood disorders: a bibliometric analysis from 1999 to 2020

Objective

Globally, mood disorders are highly prevalent, and are associated with increased morbidity and mortalities. Magnetic resonance imaging is widely used in the study of mood disorders. However, bibliometric analyses of the state of this field are lacking.

Methods

A literature search in the web of science core collection (WoSCC) for the period between 1945 and 2020 returned 3073 results. Data extracted from these publications include, publication year, journal names, countries of origin, institutions, author names and research areas. The bibliometric method, CiteSpace V and key words analysis were used to visualize the collaboration network and identify research trends, respectively.

Results

Since it was first reported in 1999, the use of magnetic resonance imaging in studies on mood disorders has been increasing. Biological psychiatry is the core journal that has extensively published on this topic, while the UNIV PITTSBURGH, USA, has the highest published papers on this topic. Keyword analysis indicated that studies on depression, bipolar disorders, and schizophrenia, with a focus on specific brain regions, including amygdala, prefrontal cortex and anterior cingulate cortex are key research topics.

Conclusion

Brain structure and network, sex differences, and treatment-associated brain changes are key topics of future research.

Animal models for the study of depressive disorder

Depressive disorder is one of the most widespread forms of psychiatric pathology, worldwide. According to a report by the World Health Organization, the number of people with depression, globally, is increasing dramatically with each year. Previous studies have demonstrated that various factors, including genetics and environmental stress, contribute to the risk of depression. As such, it is crucial to develop a detailed understanding of the pathogenesis of depressive disorder and animal studies are essential for identifying the mechanisms and genetic disorders underlying depression. Recently, many researchers have reported on the pathology of depression via various models of depressive disorder. Given that different animal models of depression show differences in terms of patterns of depressive behavior and pathology, the comparison between depressive animal models is necessary for progress in the field of the depression study. However, the various animal models of depression have not been fully compared or evaluated until now. In this paper, we reviewed the pathophysiology of the depressive disorder and its current animal models with the analysis of their transcriptomic profiles. We provide insights for selecting different animal models for the study of depression.

Cerebral Small-Vessel Disease and Risk of Incidence of Depression: A Meta-Analysis of Longitudinal Cohort Studies

Background

Results of several longitudinal cohort studies suggested an association between cerebral small‐vessel disease and depression. Therefore, we performed a meta‐analysis to explore whether cerebral small‐vessel disease imparts increased risk for incident depression.

Methods and Results

We searched prospective cohort studies relevant to the relationship between cerebral small‐vessel disease and incident depression published through September 6, 2019, which yielded 16 cohort studies for meta‐analysis based on the relative odds ratio (OR) calculated with fixed‐ and random‐effect models. Baseline white matter hyperintensities (WMHs) (pooled OR, 1.37; 95% CI, 1.14–1.65), enlarged perivascular spaces (pooled OR, 1.33; 95% CI, 1.03–1.71), and cerebral atrophy (pooled OR, 2.83; 95% CI, 1.54–5.23) were significant risk factors for incident depression. Presence of deep WMHs (pooled OR, 1.47; 95% CI, 1.05–2.06) was a stronger predictor of depression than were periventricular WMHs (pooled OR, 1.31; 95% CI, 0.93–1.86). What's more, the pooled OR increased from 1.20 for the second quartile to 1.96 for the fourth quartile, indicating that higher the WMH severity brings greater risk of incident depression (25th–50th: pooled OR, 1.20; 95% CI, 0.68–2.12; 50th–75th; pooled OR, 1.42; 95% CI, 0.81–2.46; 75th–100th: OR, 1.96; 95% CI, 1.06–3.64). These results were stable to subgroup analysis for age, source of participants, follow‐up time, and methods for assessing WMHs and depression.

Conclusions

Cerebral small‐vessel disease features such as WMHs, enlarged perivascular spaces, and cerebral atrophy, especially the severity of WMHs and deep WMHs, are risk factors for incident depression.

Depressive disorders in the elderly and dementia: An update

The relationship between depressive disorders in the elderly and dementia, particularly Alzheimer’s disease (AD), is highly complex. While the nature of this relationship is still a matter of debate, differential diagnosis and treatment remain a great clinical challenge. We review recent findings on the conundrum of depressive disorders in the elderly and AD. There is a biological continuum between depressive disorders in the elderly – or at least a subgroup of them – and AD. While elderly subjects with depression and patients with AD exhibit higher circulating levels of pro-inflammatory molecules and lower BDNF than matched controls, CSF levels of Aβ42 can discriminate AD from depressive disorders in the elderly. The role of antidepressant treatment as a strategy to minimize the risk of AD remains to be established.

A difference degree test for comparing brain networks

Recently, there has been a proliferation of methods investigating functional connectivity as a biomarker for mental disorders. Typical approaches include massive univariate testing at each edge or comparisons of network metrics to identify differing topological features. Limitations of these methods include low statistical power due to the large number of comparisons and difficulty attributing overall differences in networks to local variation. We propose a method to capture the difference degree, which is the number of edges incident to each region in the difference network. Our difference degree test (DDT) is a two-step procedure for identifying brain regions incident to a significant number of differentially weighted edges (DWEs). First, we select a data-adaptive threshold which identifies the DWEs followed by a statistical test for the number of DWEs incident to each brain region. We achieve this by generating an appropriate set of null networks which are matched on the first and second moments of the observed difference network using the Hirschberger-Qi-Steuer algorithm. This formulation permits separation of the network's true topology from the nuisance topology induced by the correlation measure that alters interregional connectivity in ways unrelated to brain function. In simulations, the proposed approach outperforms competing methods in detecting differentially connected regions of interest. Application of DDT to a major depressive disorder dataset leads to the identification of brain regions in the default mode network commonly implicated in this ruminative disorder.

Investigating the relationship between age of onset of depressive disorder and cognitive function

OBJECTIVES

Depressive disorder is commonly associated with impaired cognitive function; however, it is unclear whether the age of onset of the first episode of depression, current depression severity, or historical severity of depressive episodes are associated with cognitive performance.

METHODS

This study examined baseline cross-sectional data from the ongoing online PROTECT study. A total of 7344 participants, 50 years or older, with a history of depression and no diagnosis of dementia were divided into three groups according to age of onset of their first depressive episode: early-onset, midlife-onset, and late-onset. Performance on measures of visuospatial episodic memory, executive function, verbal working, and visual working memory were evaluated. Demographic and clinical characteristics such as age, education, and severity of symptoms during their worst previous depressive episode and current depression severity were included in multivariate regression models.

RESULTS

The late-onset depression group scored significantly lower on the verbal reasoning task than the early-onset group while there were no significant differences found on the other tasks. Midlife-onset depression participants performed better in the visual episodic memory task, but worse on the verbal reasoning task, than early-onset depression participants. Current depression severity was negatively correlated with all four cognitive domains, while historical severity score was found to be significantly associated with cognitive performance on the verbal reasoning and spatial working memory tasks.

CONCLUSIONS

The most important indicator of cognitive performance in depression appears to be current, rather than historic depression severity; however, late-onset depression may be associated with more executive impairment than an early-onset depression.

Abnormal Voxel-Wise Degree Centrality in Patients With Late-Life Depression: A Resting-State Functional Magnetic Resonance Imaging Study

OBJECTIVES

Late-life depression (LLD) has negative impacts on somatic, emotional and cognitive domains of the lives of patients. Elucidating the abnormality in the brain networks of LLD patients could help to strengthen the understanding of LLD pathophysiology, however, the studies exploring the spontaneous brain activity in LLD during the resting state remain limited. This study aimed at identifying the voxel-level whole-brain functional connectivity changes in LLD patients.

METHODS

Fifty patients with late-life depression (LLD) and 33 healthy controls were recruited. All participants underwent a resting-state functional magnetic resonance imaging scan to assess the voxel-wise degree centrality (DC) changes in the patients. Furthermore, DC was compared between two patient subgroups, the late-onset depression (LOD) and the early-onset depression (EOD).

RESULTS

Compared with the healthy controls, LLD patients showed increased DC in the inferior parietal lobule, parahippocampal gyrus, brainstem and cerebellum (p < 0.05, AlphaSim-corrected). LLD patients also showed decreased DC in the somatosensory and motor cortices and cerebellum (p < 0.05, AlphaSim-corrected). Compared with EOD patients, LOD patients showed increased centrality in the superior and middle temporal gyrus and decreased centrality in the occipital region (p < 0.05, AlphaSim-corrected). No significant correlation was found between the DC value and the symptom severity or disease duration in the patients after the correction for multiple comparisons.

CONCLUSIONS

These findings indicate that the intrinsic abnormality of network centrality exists in a wide range of brain areas in LLD patients. LOD patients differ with EOD patients in cortical network centrality. Our study might help to strengthen the understanding of the pathophysiology of LLD and the potential neural substrates underlie related emotional and cognitive impairments observed in the patients.

Ketamine and selective activation of parvalbumin interneurons inhibit stress-induced dendritic spine elimination

Stress is a major risk factor for the onset of many psychiatric diseases. In rodent models, chronic stress induces depression and impairs excitatory neurotransmission. However, little is known about the effect of stress on synaptic circuitry during the development of behavioral symptoms. Using two-photon transcranial imaging, we studied the effect of repeated restraint stress on dendritic spine plasticity in the frontal cortex in vivo. We found that restraint stress induced dendritic spine loss by decreasing the rate of spine formation and increasing the rate of spine elimination. The N-methyl-D-aspartate receptor antagonist ketamine inhibited stress-induced spine loss mainly by protecting mushroom spines from elimination. Ketamine also induced re-formation of spines in close proximity to previously stress-eliminated spines. Electrophysiological and in vivo imaging experiments showed that ketamine enhanced activity of parvalbumin (PV) interneurons under stress and counterbalanced the stress-induced net loss of PV axonal boutons. In addition, selective chemogenetic excitation of PV interneurons mimicked the protective effects of ketamine on dendritic spines against stress. Collectively, our data provide new insights on the effects of ketamine on synaptic circuitry under stress and a possible mechanism to counteract stress-induced synaptic impairments through PV interneuron activation.

Smaller hippocampal volume in current but not in past depression in comparison to healthy controls: Minor evidence from an older adults sample

BACKGROUND

Structural neuroimaging studies revealed a consistent pattern of volumetric reductions in both hippocampus (HC) and anterior cingulate cortex (ACC) of individuals with major depressive episode(s) (MDE). This study investigated HC and ACC volume differences in currently depressed individuals (n = 150), individuals with a past lifetime MDE history (n = 79) and healthy controls (n = 287).

METHODS

Non-demented individuals were recruited from a cohort of community-dwelling older adults (ESPRIT study). T1-weighted magnetic resonance images and FreeSurfer Software (automated method) were used. Concerning HC, a manual method of measurement dividing HC into head, body, and tail was also used. General Linear Model was applied adjusting for covariates.

RESULTS

Current depression was associated with lower left posterior HC volume, using manual measurement, in comparison to healthy status. However, when we slightly changed sub-group inclusion criteria, results did not survive to correction for multiple comparisons.

CONCLUSIONS

The finding of lower left posterior HC volume in currently depressed individuals but not in those with a past MDE compared to healthy controls could be related to brain neuroplasticity. Additionally, our results may suggest manual measures to be more sensitive than automated methods.

The Relationship between Fatty Acids and Different Depression-Related Brain Regions, and Their Potential Role as Biomarkers of Response to Antidepressants

Depression is a complex disorder influenced by a variety of biological and environmental factors. Due to significant heterogeneity, there are remarkable differences in how patients respond to treatment. A primary objective of psychiatric research is to identify biological markers that could be used to better predict and enhance responses to antidepressant treatments. Diet impacts various aspects of health, including depression. The fatty acid composition of the Western diet, which has a high ratio of n-6:n-3 polyunsaturated fatty acids, is associated with increased incidence of depression. The brain is rich in lipids, and dietary fatty acids act within specific brain regions to regulate processes that impact emotional behavior. This manuscript reviews existing evidence demonstrating brain region-specific fatty acid profiles, and posits that specific fatty acids may serve as predictive biomarkers of response to antidepressants. Furthermore, increasing blood levels of certain fats, such as n-3s, via dietary intervention may serve as an adjunct to improve the efficacy of antidepressants. Notably, most of the existing research regarding fats and depression-related brain regions has focused on n-3s, as compared to n-6s, monounsaturated, and saturated fats. This review article will help guide future work investigating the relationships between fatty acids, brain regions, and antidepressant efficacy.

Influence of age of onset on limbic and paralimbic structures in depression

AIM

Major depressive disorder (MDD) onset during childhood/adolescence is associated with a greater illness burden and distinct clinical profile. However, limited research exists on the effect of age of MDD onset on volumetric abnormalities in para/limbic structures during adulthood.

METHODS

Subgenual anterior cingulate cortex (sgACC), hippocampus and caudate nucleus volumes were measured by manual tracing in depressed individuals (n = 45) and healthy controls (HC; n = 19). Volumetric comparisons were carried out between HC and MDD patients divided into those with pediatric (≤ 18 years; n = 17) and adult onset (≥ 19 years; n = 28).

RESULTS

The adult MDD-onset group had smaller sgACC volumes than the pediatric-onset and HC groups (age, sex controlled). No differences in caudate and hippocampus volumes existed. sgACC and hippocampal volumes were inversely correlated with depression severity.

CONCLUSIONS

Surprisingly, pediatric MDD-onset was not associated with more pronounced sgACC, hippocampus and caudate volume reductions. Nevertheless, age of illness onset appears to be a meaningful dimension of study in efforts to understand the neurobiological heterogeneity of MDD.

Soluble amyloid-β levels and late-life depression

Late-Life Major Depression (LLMD) is a complex heterogeneous disorder that has multiple pathophysiological mechanisms such as medical comorbidity, vascular-related factors and Alzheimer's disease (AD). There is an association between LLMD and AD, with LLMD possibly being a risk factor for, or early symptom of AD and vascular dementia. Whether depression is an etiologic risk factor for dementia, or part of the dementia prodrome remains controversial. AD has a long prodromal period with the neuropathologic features of the disease preceding the onset of clinical symptoms by as much as 15-20 years. Clinicopathological studies have provided robust support for the importance of Aβ42 in the pathogenesis of AD, but several other risk factors have also been identified. Given the relationship between Aβ42 and AD, a potential relationship between Aβ42 and LLMD would improve the understanding of the association between LLMD and AD. We reviewed 15 studies that analyzed the relationship between soluble Aβ42 and LLMD. For studies looking at plasma and/or cerebrospinal fluid (CSF) levels of Aβ42, the relationship between LLMD and soluble Aβ42 was equivocal, with some studies finding elevated Aβ42 levels associated with LLMD and others finding the opposite, decreased levels of Aβ42 associated with LLMD. It may be that there is poor reliability in the diagnosis of depression in late life, or variability in the criteria and the scales used, or subtypes of depression in late life such as early vs. late onset depression, vascular-related depression, and preclinical/comorbid depression in AD. The different correlations associated with each of these factors would be causing the inconsistent results for soluble Aβ42 levels in LLMD, but it is also possible that these patterns derive from disease stage-dependent differences in the trajectory of CSF Aβ42 during older age, or changes in neuronal activity or the sleep/wake cycle produced by LLMD that influence Aβ42 dynamics.

Alzheimer's disease pathology does not mediate the association between depressive symptoms and subsequent cognitive decline

BACKGROUND

Depressive symptoms in nondemented individuals appear to hasten the progression from mild cognitive impairment to clinical Alzheimer's disease (AD) and double the risk of incident AD. However, the mechanism(s) by which depression might affect this risk has not been well established. The purpose of this analysis was to test the hypothesis that AD pathology mediates depression's apparent effect on the risk of dementia conversion using longitudinally collected psychometric testing and autopsy data from the Honolulu-Asia Aging Study.

METHODS

Latent factor variables representing AD, cortical Lewy body (CLB), and ischemic neuropathology were tested as potential mediators of the association between the Center for Epidemiological Studies depression scale (CES-D) score and the 10-year prospective rate of cognitive decline, adjusted for baseline cognition, age, education, total number of medications, and brain weight at autopsy.

RESULTS

CES-D scores, neurofibrillary tangle counts, CLB counts, and ischemic lesions each made significant independent contributions to cognitive decline. However, CES-D scores were not significantly associated with any pathological variable; thus the pathological variables were not mediators of the effect of CES-D scores on cognitive decline.

CONCLUSIONS

Subsyndromal depressive symptoms are significantly associated with subsequent cognitive decline. Although the effect is relatively modest, it is stronger than that of amyloid-related neuropathologies and independent of that of neurofibrillary tangles, cortical Lewy bodies, and ischemic lesions. Our results argue against the role of AD-related neuropathology as a mediator of depression's effect on cognitive decline, but cannot rule out a significant mediation effect in a subset of cases, perhaps with more severe baseline depressive symptoms.

Organic bases of late-life depression: a critical update

Late-life depression (LLD) is frequently associated with cognitive impairment and increases the risk of subsequent dementia. Cerebrovascular disease, deep white matter lesions, Alzheimer disease (AD) and dementia with Lewy bodies (DLB) have all been hypothesized to contribute to this increased risk, and a host of studies have looked at the interplay between cerebrovascular disease and LLD. This has resulted in new concepts of LLD, such as "vascular depression", but despite multiple magnetic resonance imaging (MRI) studies in this field, the relationship between structural changes in human brain and LLD is still controversial. While pathological findings of suicide in some elderly persons revealed multiple lacunes, small vessel cerebrovascular disease, AD-related lesions or multiple neurodegenerative pathologies, recent autopsy data challenged the role of subcortical lacunes and white matter lesions as major morphological substrates of depressive symptoms as well as poorer executive function and memory. Several neuropathological studies, including a personal clinico-pathological study in a small cohort of elderly persons with LLD and age-matched controls confirmed that lacunes, periventricular and deep white matter demyelination as well as AD-related lesions are usually unrelated to the occurrence of LLD. In the same line, neuropathological data show that early-onset depression is not associated with an acceleration of age-related neurodegenerative changes. Very recent data on the critical role of glia-modulating neuronal dysfunction and degeneration in depression are discussed.

Where in the brain is depression?

Major depressive disorder is a serious medical illness which is responsible for considerable morbidity and disability. Despite decades of research, the neural basis for depression is still incompletely understood. In this review, evidence from neuroimaging, neuropsychiatric and brain stimulations studies are explored to answer the question regarding the localization of depression in the brain. Neuroimaging studies indicate that although many regions of the brain have been repeatedly implicated in the pathophysiology of depression, not many consistent findings have been found until present. In recent times, the focus of neuroimaging has shifted from regional brain abnormalities to circuit level connectivity abnormalities. However, connectivity models are inherently more complicated, and the validity of these models remains to be tested. Neuropsychiatric studies of illnesses such as Parkinson's disease and stroke provide promising clues regarding areas involved in depression, but again consistent findings are rare. Similarly, stimulation of a variety of brain regions and circuits has been reported as being effective in depression. Therefore, the current knowledge indicates that the pathophysiology of depression may be distributed across many brain regions and circuits. In future studies, this distributed nature of depression needs to be further investigated, primary and secondary areas affected need to be identified, and new paradigms to explain complex mental functions need to be explored.

The role of glia in late-life depression

Late-life depression (LLD) has a complex and multifactoral etiology. There is growing interest in elucidating how glia, acting alone or as part of a glial-neuronal network, may contribute to the pathophysiology of depression. In this paper, we explore results from neuroimaging studies showing gray-matter volume loss in key frontal and subcortical structures implicated in LLD, and present the few histological studies that have examined neuronal and glial densities in these regions. Compared to results in younger people with depression, there appear to be age-dependent differences in neuronal pathology but the changes in glial pathology may be more subtle, perhaps reflecting a longer-term compensatory gliosis to earlier damage. We then consider the mechanisms by which both astrocytes and microglia may mediate and modulate neuronal dysfunction and possible degeneration in depression. These include a critical role in the response to peripheral inflammation and central microglial activation, as well as a key role in glutamate metabolism. Advances in our understanding of glia are highlighted, including the role of microglia as "electricians" of the brain and astrocytes as key communicating cells, an integral part of the tripartite synapse. Finally, implications for clinicians are discussed, including the consideration of glia as biomarkers for LLD and incorporation of glia into future therapeutic strategies.

A randomized double-blind sham-controlled comparison of unilateral and bilateral repetitive transcranial magnetic stimulation for treatment-resistant major depression

OBJECTIVES

High frequency left-sided (HFL) and low frequency right-sided (LFR) unilateral repetitive transcranial magnetic stimulation (rTMS) are efficacious in treatment-resistant major depression (TRD). Similar benefit has been suggested for sequential bilateral rTMS (LFR then HFL). There are few published reports on the efficacy of sequential bilateral rTMS compared to HFL and sham rTMS. Therefore, this study evaluated the efficacy of HFL and sequential bilateral rTMS compared to sham in TRD.

METHODS

Subjects between the ages of 18 and 85 were recruited from a tertiary care university hospital. Seventy-four subjects with TRD and a 17-item Hamilton Depression Rating Scale (HDRS) greater than 21 were randomized to receive unilateral, bilateral, or sham rTMS. The rates of remission were compared among the three treatment groups.

RESULTS

The remission rates differed significantly among the three treatment groups using a modified intention to treat analysis that excluded subjects who did not respond to electroconvulsive therapy (ECT) during the current episode. The remission rate was significantly higher in the bilateral group than the sham group. The remission rate in the unilateral group did not differ from either group.

CONCLUSION

These findings warrant larger controlled studies that compare the efficacy of sequential bilateral rTMS and HFL rTMS in TRD.

Meta-analysis of volumetric abnormalities in cortico-striatal-pallidal-thalamic circuits in major depressive disorder

BACKGROUND

Abnormalities in cortico-striatal-pallidal-thalamic (CSPT) circuits have been implicated in major depressive disorder (MDD). However, the robustness of these findings across studies is unclear, as is the extent to which they are influenced by demographic, clinical and pharmacological factors.

METHOD

With the aim of clarifying these questions, we conducted a meta-analysis to map the volumetric abnormalities that were most robustly identified in CSPT circuits of individuals with MDD. A systematic search identified 41 studies meeting our inclusion criteria.

RESULTS

There were significant volume reductions in prefrontal (especially orbitofrontal) and anterior cingulate cortices, and also in subcortical structures such as the caudate nucleus and putamen, with effect sizes ranging from small to moderate. The subgenual anterior cingulate and orbitofrontal cortices were significantly smaller in antidepressant-free samples compared to medicated patients. Late-life depression (LLD) tended to be associated with smaller volumes in circumscribed frontal and subcortical structures, with the most robust differences being found in thalamic volume.

CONCLUSIONS

Individuals with major depression demonstrate volumetric abnormalities of CSPT circuits. However, these observations may be restricted to certain subgroups, highlighting the clinical heterogeneity of the disorder. On the basis of this meta-analysis, CSPT abnormalities were more prominent in those with LLD whereas antidepressant use seemed to normalize certain cortical volumetric abnormalities.

Depressive symptoms predict longitudinal change in executive control but not memory

OBJECTIVE

Depression in non-demented persons has been identified as a possible risk factor for incident Alzheimer's disease (AD).

METHODS

Latent Growth Curve models were developed of baseline depressive symptoms as a predictor of longitudinal changes in cognition. Depressive symptoms were assessed using the 15-item Geriatric Depression Scale (GDS). Memory was assessed by the California Verbal Learning Task (CVLT). Executive control function (ECF) was assessed by the Executive Interview (EXIT25) and Trail-Making Test Part B (Trails-B). Five hundred forty-seven non-institutionalized older retirees living in a single comprehensive care retirement community participated.

RESULTS

Depressive symptoms were significantly associated only with the 3-year rate of decline in psychomotor speed, as measured by Trails A, and ECF, as measured by the EXIT25. Both associations withstood adjustment for age, gender, education, and baseline level of care.

CONCLUSIONS

Depressive symptoms are associated with longitudinal decline in cognition. However, this association selectively involves executive control, not memory, and possibly only a subset of 'executive' functions. Although depressive symptoms may hasten conversion from mild cognitive impairment (MCI) to dementia, depression-related conversion is not likely to be mediated by evolution of the AD pathological process.

Psychiatric disorders in the elderly

Recent research has shown that depression, anxiety disorders, and psychosis are more common than previously supposed in elderly populations without dementia. It is unclear whether the frequency of these disorders increases or decreases with age. Clinical expression of psychiatric disorders in old age may be different from that seen in younger age groups, with less and often milder symptoms. Concurrently, comorbidity between different psychiatric disorders is immense, as well as comorbidity with somatic disorders. Cognitive function is often decreased in people with depression, anxiety disorders, and psychosis, but whether these disorders are risk factors for dementia is unclear. Psychiatric disorders in the elderly are often related to cerebral neurodegeneration and cerebrovascular disease, although psychosocial risk factors are also important. Psychiatric disorders, common among the elderly, have consequences that include social deprivation, poor quality of life, cognitive decline, disability, increased risk for somatic disorders, suicide, and increased nonsuicidal mortality.

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 pattern and course of cognitive impairment in late-life depression

BACKGROUND

Cognitive deficits persist despite clinical recovery in subjects with late-life depression, but more needs to be known about their longer-term outcome and factors affecting their course. To investigate this, we followed the pattern of cognitive impairments over time and examined the effects of current mood, remission status, age of depression onset and antidepressant (AD) treatment on these deficits.

METHOD

Sixty-seven subjects aged > or = 60 years with DSM-IV major depressive disorder and 36 healthy comparison subjects underwent tests of global cognition, memory, executive functioning and processing speed at baseline, 6 and 18 months, with some subjects tested again after 4 years. z scores were compared between groups, with analyses of clinical factors that may have influenced cognitive performance in depressed subjects.

RESULTS

Half of the patients exhibited a generalized cognitive impairment (GCI) that persisted after 18 months. Patients performed worse across all cognitive domains at all time points, without substantial variability due to current mood, remission status or AD treatment. Late age of onset was associated significantly with decline in memory and executive functioning. Impaired processing speed may be a partial mediator of some deficits, but was insufficient to explain differences between patients and controls. Four-year follow-up data suggest impairments persist, but do not further decline.

CONCLUSIONS

Cognitive deficits in late-life depression persist up to 4 years, affect multiple domains and are related to trait rather than state effects. Differences in severity and course between early and late onset depression suggest different pathogenic processes.

White matter hyperintensities, cortisol levels, brain atrophy and continuing cognitive deficits in late-life depression

BACKGROUND

Cerebrovascular changes and glucocorticoid mediated hippocampal atrophy are considered relevant for depression-related cognitive deficits, forming putative treatment targets.

AIMS

This study examined the relative contribution of cortisol levels, brain atrophy and white matter hyperintensities to the persistence of cognitive deficits in older adults with depression.

METHOD

Thirty-five people aged > or =60 years with DSM-IV major depression and twenty-nine healthy comparison controls underwent magnetic resonance imaging (MRI) and were followed up for 18 months. We analysed the relationship between baseline salivary cortisol levels, whole brain, frontal lobe and hippocampal volumes, severity of white matter hyperintensities and follow-up cognitive function in both groups by testing the interaction between the groups and these biological measures on tests of memory, executive functions and processing speed in linear regression models.

RESULTS

Group differences in memory and executive function follow-up scores were associated with ratings of white matter hyperintensities, especially of the deep white matter and periventricular regions. Compared with healthy controls, participants with depression scoring within the third tertile of white matter hyperintensities dropped two and three standard deviations in executive function and memory scores respectively. No biological measure related to group differences in processing speed, and there were no significant interactions between group and cortisol levels, or volumetric MRI measures.

CONCLUSIONS

White matter hyperintensities, rather than cortisol levels or brain atrophy, are associated with continuing cognitive impairments in older adults with depression. The findings suggest that cerebrovascular disease rather than glucocorticoid-mediated brain damage are responsible for the persistence of cognitive deficits associated with depression in older age.

Volumetric neuroimaging investigations in mood disorders: bipolar disorder versus major depressive disorder

BACKGROUND

As patients with mood disorders manifest heterogeneity in phenomenology, pathophysiology, etiology, and treatment response, a biological classification of mental disease is urgently needed to advance research. Patient and methodological variability complicates the comparison of neuroimaging study results and limits heuristic model development and a biologically-based diagnostic schema.

OBJECTIVE

We have critically reviewed and compared the magnetic resonance neuroimaging literature to determine the degree and directionality of volumetric changes in brain regions putatively implicated in the pathophysiology of major depressive disorder (MDD) versus bipolar disorder (BD).

METHODS

A total of 140 published magnetic resonance imaging investigations evaluating subjects with BD or MDD were selected to provide a summary and interpretation of volumetric neuroimaging results in MDD and BD. Further commentary on the pathophysiological implications, and putative cellular and pharmacological mechanisms, is also provided.

RESULTS

While whole brain volumes of patients with mood disorders do not differ from those of healthy controls, regional deficits in the frontal lobe, particularly in the anterior cingulate and the orbitofrontal cortex, appear to consistently differentiate subjects with mood disorders from the general population. Preliminary findings also suggest that subcortical structures, particularly the striatum, amygdala, and hippocampus, may be differentially affected in MDD and BD.

CONCLUSIONS

Structural neuroimaging studies have consistently identified regional abnormalities in subjects with mood disorders. Future studies should strive to definitively establish the influence of age and medication.

Melancholic major depression and epilepsy

An analysis is carried out of a set of psychic phenomena appearing always in the same way: an experience suddenly invades the consciousness, unfolding automatically and with great intensity. This psychic automatism, of which the patient is a passive observer, is accompanied by an overwhelming feeling of strangeness. Our hypothesis is that these phenomena are the expression of partial seizures with a psychic content, and the name Paroxysmal Psychic Automatisms is proposed for all of them. A comparative study is then made of the phenomenology of partial seizures with a psychic content, on the one hand, and of that of melancholic major depression, on the other. It reveals a wealth of clinical information indicating an overlap between the two conditions. Finally, a set of well-established scientific data is analysed concerning epilepsy and depression, especially epidemiological and psychopharmacological information, which takes on a new meaning in the light of the hypothesis developed in this paper.

Data from the VITA Study do not support the concept of vascular depression

OBJECTIVE

Cerebrovascular lesions that are apparent in magnetic resonance scans and regioselective atrophy of the brain have been proposed as a causative or exacerbating factor in depression with late-life onset. The objective of this study was to investigate whether deep white matter or periventricular hyperintensities, small ischemic lesions, and brain atrophy contribute to late-onset depression in the nondemented elderly.

METHOD

Based on a group of 606 individuals of identical age (75.8 years, standard deviation: 0.45 years) residing in two districts of Vienna, the authors built a case-control cohort (ratio: 1:4) consisting of 51 individuals with late-onset major or minor depression matched with 204 subjects of identical gender and education status without depression, resulting in two groups that were homogenous with respect to age, place of residence, gender, and education. Scores for focal brain lesions, mediotemporal lobe atrophy, and ventricular enlargement as well as risk factors for vascular disease were compared with cognition and depression status.

RESULTS

Depressed individuals had significantly lower scores than nondepressed subjects in all measures of cognitive and executive function. No significant relation was found between a diagnosis of depression and any type of discrete brain lesions, but measures of brain atrophy (Cella Media indices, mediotemporal atrophy) showed a clear statistical relation to depression. No relationship was found between depression and lipid parameters.

CONCLUSION

The authors found no indication that white matter hyperintensities or minor ischemic lesions played a role in our depressed cohort, casting doubt on the vascular hypothesis of late-onset depression.

Depressive symptoms and white matter changes in patients with dementia

OBJECTIVE

The aim of the present study was to investigate if depressive symptoms in demented patients are associated with white matter changes (WMCs) in the brain.

BACKGROUND

WMCs are frequently found in patients with dementia, as well as among elderly nondemented patients with depressive symptoms. However, it is less established whether or not WMCs are related to depressive symptoms in demented patients.

METHODS

67 (26 men, 41 women) patients with primary degenerative dementia (Alzheimer's disease, frontotemporal dementia), vascular dementia (VaD), or mixed Alzheimer/VaD dementia were included in the study. The patients were young-old (mean 68.1, SD 7.3). All patients underwent a standardized examination procedure and MRI of the brain. The degree of WMCs was visually rated, blindly. Depressive symptoms were rated according to the Gottfries-Bråne-Steen scale (anxiety, fear-panic, depressed mood).

RESULTS

No significant relationship was found between WMCs and depressive symptoms in the demented patients.

CONCLUSION

The possible involvement of WMCs in the pathogenesis of depressive symptoms in dementia is unclear. A link between disruptions of frontal-subcortical pathways, due to WMCs, and depressive symptomatology in dementia has been hypothesised from earlier findings, which would imply common elements of pathogenesis for depressive symptomatology and cognitive impairment in dementia. However, the results of the present study do not add further support to this hypothesis.