Is there a dysfunction in the visual system of depressed patients?

The electroretinography to identify biomarkers of idiopathic hypersomnia and narcolepsy type 1

Hypersomnia spectrum disorders are underdiagnosed and poorly treated due to their heterogeneity and absence of biomarkers. The electroretinography has been proposed as a proxy of central dysfunction and has proved to be valuable to differentiate certain psychiatric disorders. Hypersomnolence is a shared core feature in central hypersomnia and psychiatric disorders. We therefore aimed to identify biomarkers by studying the electroretinography profile in patients with narcolepsy type 1, idiopathic hypersomnia and in controls. Cone, rod and retinal ganglion cells electrical activity were recorded with flash-electroretinography in non-dilated eye of 31 patients with idiopathic hypersomnia (women 84%, 26.6 ± 5.9 years), 19 patients with narcolepsy type 1 (women 63%, 36.6 ± 12.7 years) and 43 controls (women 58%, 30.6 ± 9.3 years). Reduced cone a-wave amplitude (p = 0.039) and prolonged cone (p = 0.022) and rod b-wave (p = 0.009) latencies were observed in patients with narcolepsy type 1 as compared with controls, while prolonged photopic negative response-wave latency (retinal ganglion cells activity) was observed in patients with idiopathic hypersomnia as compared with controls (p = 0.033). The rod and cone b-wave latency clearly distinguished narcolepsy type 1 from idiopathic hypersomnia and controls (area under the curve > 0.70), and the photopic negative response-wave latency distinguished idiopathic hypersomnia and narcolepsy type 1 from controls with an area under the curve > 0.68. This first original study shows electroretinography anomalies observed in patients with hypersomnia. Narcolepsy type 1 is associated with impaired cone and rod responses, whereas idiopathic hypersomnia is associated with impaired retinal ganglion cells response, suggesting different phototransduction alterations in both hypersomnias. Although these results need to be confirmed with a larger sample size, the electroretinography may be a promising tool for clinicians to differentiate hypersomnia subtypes.

Differentiating melancholic and non-melancholic depression via biological markers: A review

OBJECTIVES

Melancholia is a severe form of depression that is typified by greater genetic and biological influence, distinct symptomatology, and preferential response to physical treatment. This paper sought to broadly overview potential biomarkers of melancholia to benefit differential diagnosis, clinical responses and treatment outcomes. Given nuances in distinguishing melancholia as its own condition from other depressive disorder, we emphasised studies directly comparing melancholic to non-melancholic depression.

METHODS

A comprehensive literature search was conducted. Key studies were identified and summarised qualitatively.

RESULTS

105 studies in total were identified. These studies covered a wide variety of biomarkers, and largely fell into three domains: endocrinological (especially cortisol levels, particularly in response to the dexamethasone suppression test), neurological, and immunological (particularly inflammatory markers). Less extensive evidence also exists for metabolic, genetic, and cardiovascular markers.

CONCLUSIONS

Definitive conclusions were predominantly limited due to substantial heterogeneity in how included studies defined melancholia. Furthermore, this heterogeneity could be responsible for the between- and within-group variability observed in the candidate biomarkers that were examined. Therefore, clarifying these definitional parameters may help identify underlying patterns in biomarker expression to improve diagnostic and therapeutic precision for the depressive disorders.

Sex-Specific Retinal Anomalies Induced by Chronic Social Defeat Stress in Mice

Major depressive disorder (MDD) is one of the most common consequences of chronic stress. Still, there is currently no reliable biomarker to detect individuals at risk to develop the disease. Recently, the retina emerged as an effective way to investigate psychiatric disorders using the electroretinogram (ERG). In this study, cone and rod ERGs were performed in male and female C57BL/6 mice before and after chronic social defeat stress (CSDS). Mice were then divided as susceptible or resilient to stress. Our results suggest that CSDS reduces the amplitude of both oscillatory potentials and a-waves in the rods of resilient but not susceptible males. Similar effects were revealed following the analysis of the cone b-waves, which were faster after CSDS in resilient mice specifically. In females, rod ERGs revealed age-related changes with no change in cone ERGs. Finally, our analysis suggests that baseline ERG can predict with an efficacy up to 71% the expression of susceptibility and resilience before stress exposition in males and females. Overall, our findings suggest that retinal activity is a valid biomarker of stress response that could potentially serve as a tool to predict whether males and females will become susceptible or resilient when facing CSDS.

Decreased dynamism of overlapping brain sub-networks in Major Depressive Disorder

Major Depressive Disorder (MDD) is increasingly recognized as a common brain disorder with aberrant brain networks. Alterations in dynamic functional brain networks have been widely reported in MDD. However, previous studies mainly focused on detecting non-overlapping sub-networks/communities, neglecting the possibility that one brain region may belong to multiple sub-networks/communities. In the present work, we utilized tensor decomposition method to detect overlapping communities and study the dynamism of overlapping sub-networks through 58 patients with MDD and 63 age- and sex-matched healthy controls (HC). The strength vectors of communities were calculated and two-sample t-test was performed to investigate the statistical significance of the differences in dynamism of MDD and HC groups. We found that communities detected in two groups were pairwise region-matching but overlapped brain regions were almost totally different. We considered two region-matching communities in the two groups as a sub-network. Compared to HCs, MDD patients showed significantly decreased dynamism in five sub-networks which could be functionally mapped to Visual Network (VN), Default Mode Network (DMN), Cognitive Control Network (CCN), Bilateral Limbic Network (BLN) and Auditory Network (AN). The results showed that MDD might only have a marginal effect on the holistic detection of communities and the changes of overlapped brain regions in MDD patients might be put down to the alteration of hubs. Further statistical analysis on nine sub-networks showed decreased dynamism of five sub-networks in MDD patients, which might help us achieve a better understanding of mechanism in MDD.

[Retinal investigations in patients with major depressive disorder, bipolar disorder or schizophrenia: A review of the literature]

Major depressive disorder, bipolar disorder and schizophrenia are currently among the most common psychiatric disorders, known to constitute a serious public health issue in terms of morbidity, mortality and functional handicap. Their pathophysiology is still unclear, but there is now increasing evidence supporting the existence of abnormalities of neurotransmission. As the retina is an extension of the central nervous system, it may be an interesting site of study which might provide a better understanding of the pathophysiology of psychiatric disorders. Several studies have demonstrated retinal abnormalities, with abnormal cone and rod responses on electroretinography (ERG), suggesting a process of functional neuronal loss, structurally supported by a decrease in the retinal nerve fiber layer thickness (RNFL) on optical coherence tomography (OCT), which suggests involvement of the molecular signal pathways of neurotransmission. These tests could be useful tools for diagnosing and monitoring psychiatric disorders. This article is an overview of the literature on retinal abnormalities observed in patients with major depressive disorder, bipolar disorder or schizophrenia, and discusses how they could be pathophysiologic markers.

New insights on the role of the retina in diagnostic and therapeutic strategies in major depressive disorder

Major depressive disorder (MDD) affects people worldwide. MDD treatments include antidepressants, which involve a delayed onset of action, long-term treatment, side effects and, frequently, only partial efficacy. The lack of access to the living brain, and the complex and still poorly elucidated pathophysiology of MDD, hinders treatment development. There is not only a need for new treatment strategies, but also for new approaches to investigating the pathophysiology of MDD. Light therapy is a well-established treatment acting through the retina. Since the retina is part of the central nervous system, it has been suggested as a useful area for investigating mental illness. In this article, we will first set out the evidence that MDD affects the retina's structure and function. We will then review studies evaluating the efficacy of light therapy in unipolar non-seasonal MDD. Finally, we discuss the disruption of melatoninergic pathways in MDD, its assessment through the retina and the treatment of this disruption with light therapy.

Study of retinal structure and function in patients with major depressive disorder, bipolar disorder or schizophrenia: A review of the literature

Major depressive disorder, bipolar disorder and schizophrenia are currently among the most common psychiatric disorders, known to constitute a serious public health issue in terms of morbidity, mortality and functional handicap. Their pathophysiology is still unclear, but there is now increasing evidence supporting the existence of abnormalities of neurotransmission. As the retina is an extension of the central nervous system, it may be an interesting site of study which might provide a better understanding of the pathophysiology of psychiatric disorders. Several studies have demonstrated retinal abnormalities, with abnormal cone and rod responses on electroretinography (ERG), suggesting a process of functional neuronal loss, structurally supported by a decrease in the retinal nerve fiber layer thickness (RNFL) on optical coherence tomography (OCT), which suggests involvement of the molecular signal pathways of neurotransmission. These tests could be useful tools for diagnosing and monitoring psychiatric disorders. This article is an overview of the literature on retinal abnormalities observed in patients with major depressive disorder, bipolar disorder or schizophrenia, and discusses how they could be pathophysiologic markers.

People with current major depression resemble healthy controls on flash Electroretinogram indices associated with impairment in people with stabilized schizophrenia

Flash electroretinography (fERG) has been used to identify anomalies in retinal functioning in several psychiatric disorders. In schizophrenia (SCZ), fERG abnormalities are reliably observed, but findings from studies of major depressive disorder (MDD) have been less consistent. In this study, fERG data were recorded from MDD patients in a current major depressive episode (n = 25), and compared to data from SCZ patients (n = 25) and healthy controls (HC; n = 25), to determine the degree to which fERG anomalies in acute MDD overlap or contrast with those observed in stabilized (though not symptom free) SCZ. The primary variables of interest were a-wave (photoreceptor activity), b-wave (bipolar-Müller cell activity), and photopic negative response (PhNR; ganglion cell activity) amplitudes and implicit times. Across most conditions, there were no significant differences between the MDD and HC groups in a- or b-wave response, but the SCZ group consistently demonstrated reduced amplitudes. Interestingly, MDD patients demonstrated an increase in photopic a-wave implicit time relative to SCZ patients, and a decrease in PhNR implicit time relative to controls. Correlations between BDI-II scores and fERG metrics were not significant for either patient group. Overall, these data indicate that, using an fERG protocol that distinguishes SCZ patients from controls, MDD patients experiencing a current depressive episode closely resemble healthy controls in their fERG responses. Therefore, MDD-related fERG changes may be more subtle than those observed in SCZ and detectable only with larger sample sizes than we employed and/or using a different set of fERG test parameters.

Resting state functional connectivity predictors of treatment response to electroconvulsive therapy in depression

There is increasing focus on use of resting-state functional connectivity (RSFC) analyses to subtype depression and to predict treatment response. To date, identification of RSFC patterns associated with response to electroconvulsive therapy (ECT) remain limited, and focused on interactions between dorsal prefrontal and regions of the limbic or default-mode networks. Deficits in visual processing are reported in depression, however, RSFC with or within the visual network have not been explored in recent models of depression. Here, we support prior studies showing in a sample of 18 patients with depression that connectivity between dorsal prefrontal and regions of the limbic and default-mode networks serves as a significant predictor. In addition, however, we demonstrate that including visual connectivity measures greatly increases predictive power of the RSFC algorithm (>80% accuracy of remission). These exploratory results encourage further investigation into visual dysfunction in depression, and use of RSFC algorithms incorporating the visual network in prediction of response to both ECT and transcranial magnetic stimulation (TMS), offering a new framework for the development of RSFC-guided TMS interventions in depression.

Cannabis use and human retina: The path for the study of brain synaptic transmission dysfunctions in cannabis users

Owing to the difficulty of obtaining direct access to the functioning brain, new approaches are needed for the indirect exploration of brain disorders in neuroscience research. Due to its embryonic origin, the retina is part of the central nervous system and is well suited to the investigation of neurological functions in psychiatric and addictive disorders. In this review, we focus on cannabis use, which is a crucial public health challenge, since cannabis is one of the most widely used addictive drugs in industrialized countries. We first explain why studying retinal function is relevant when exploring the effects of cannabis use on brain function. Next, we describe both the retinal electrophysiological measurements and retinal dysfunctions observed after acute and regular cannabis use. We then discuss how these retinal dysfunctions may inform brain synaptic transmission abnormalities. Finally, we present various directions for future research on the neurotoxic effects of cannabis use.

Optic coherence tomography shows inflammation and degeneration in major depressive disorder patients correlated with disease severity

BACKGROUND

Previous research has consistently detected inflammation in the etiology of depression and neuroimaging studies have demonstrated gray matter abnormalities implying a neurodegenerative process in depression. The aim of this study was to compare ganglion cell layer (GCL), and inner plexiform layer (IPL) volumes and retinal nerve fiber layer (RNFL) thickness between first episode and recurrent major depressive disorder (MDD) patients and controls using optic coherence tomography (OCT) in order to detect findings supporting a degenerative process. Also choroid thicknesses of the same groups were compared to examine effects of inflammation on MDD.

METHODS

This study included 50 recurrent MDD patients, 50 first episode MDD patients and 50 controls. OCT measurements were performed by a spectral OCT device. GCL and IPL volumes and RNFL and choroid thicknesses were measured automatically by the device.

RESULTS

GCL and IPL volumes were significantly smaller in recurrent depression patients than first episode patients and in all MDD patients than controls. Also there were significant negative correlations between their volumes and disease severity parameters such as Ham-D and CGI scores, and disease duration. RNFL thicknesses were also lower in recurrent MDD patients than first episode patients and all MDD patients than controls but statistical significance was achieved only for global RNFL and temporal superior RNFL. Mean choroid thickness was higher in MDD patients than controls and in first episode MDD patients than recurrent MDD patients.

LIMITATIONS

Cross-sectional design of our study limits conclusions about progressive degeneration during the course of MDD. Lack of a control neuroimaging method like magnetic resonance imaging makes it hard to draw firm conclusions from our results.

CONCLUSIONS

OCT finding of decreased GCL and IPL volumes supports previous research suggesting degeneration in MDD. OCT may be an important tool to track neurodegeneration in patients with major depression. Considering RNFL to be the latest layer that will be affected during course of degeneration, GCL and IPL volumes appear to be better parameters to follow. In addition, choroid may be an important structure to detect acute attack period and to follow inflammatory process in MDD like in systemic inflammatory diseases.

The emerging field of retinal electrophysiological measurements in psychiatric research: A review of the findings and the perspectives in major depressive disorder

Major depressive disorder (MDD) is a severe mental illness leading to long-term disabilities. One of the current challenges in psychiatric research is to develop new approaches to investigate the pathophysiology of MDD and monitor drug response in order to provide better therapeutic strategies to the patients. Since the retina is considered as part of the central nervous system, it was suggested that it constitutes an appropriate site to investigate mental illnesses. In the past years, several teams assessed the retinal function of patients with mood disorders and many relevant abnormalities have been reported. Investigation of the retinal electrophysiological abnormalities in MDD remains a young emerging field, but we believe that the current findings are very promising and we argue that objective retinal electrophysiological measurements may eventually become relevant tools to investigate the pathophysiology of MDD. Here, we review the retinal abnormalities detected with objective electrophysiological measurements such as the flash electroretinogram (fERG), the pattern electroretinogram (PERG) and the electrooculogram (EOG) in patients with MDD. We discuss how these changes might reflect the pathophysiology of MDD in both clinical and scientific points of view, according especially to the monoamine neurotransmission deficiency hypothesis. We also discuss the technical details that must be taken into consideration for a potential use of the objective retinal electrophysiological measurements as tools to investigate the pathophysiology of MDD.

Relationship between sunlight and the age of onset of bipolar disorder: an international multisite study

BACKGROUND

The onset of bipolar disorder is influenced by the interaction of genetic and environmental factors. We previously found that a large increase in sunlight in springtime was associated with a lower age of onset. This study extends this analysis with more collection sites at diverse locations, and includes family history and polarity of first episode.

METHODS

Data from 4037 patients with bipolar I disorder were collected at 36 collection sites in 23 countries at latitudes spanning 3.2 north (N) to 63.4 N and 38.2 south (S) of the equator. The age of onset of the first episode, onset location, family history of mood disorders, and polarity of first episode were obtained retrospectively, from patient records and/or direct interview. Solar insolation data were obtained for the onset locations.

RESULTS

There was a large, significant inverse relationship between maximum monthly increase in solar insolation and age of onset, controlling for the country median age and the birth cohort. The effect was reduced by half if there was no family history. The maximum monthly increase in solar insolation occurred in springtime. The effect was one-third smaller for initial episodes of mania than depression. The largest maximum monthly increase in solar insolation occurred in northern latitudes such as Oslo, Norway, and warm and dry areas such as Los Angeles, California.

LIMITATIONS

Recall bias for onset and family history data.

CONCLUSIONS

A large springtime increase in sunlight may have an important influence on the onset of bipolar disorder, especially in those with a family history of mood disorders.

No differences between drug naive and drug experienced unipolar depressed patients in terms of neurobiological testing: a cross sectional study

Successful antidepressant treatment has been associated with concomitant changes in brain function, consolidated as long as treatment is continued and remission is preserved. The present study aimed at assessing the impact of prior antidepressant treatment on brain function in currently depressed but unmedicated individuals by investigating for any differences between antidepressant-naïve vs. antidepressant-experienced subjects. Fifty right-handed patients (22 medication-naïve vs. 28 medication-experienced), suffering from major depression participated in the study. They all underwent a standardised clinical interview and psychometric assessment combined with neurobiological tests (brain SPECT, Dexamethasone Suppression Test, Dexfenfluramine Challenge Test, electro-oculogram, flash-electroretinogram and flash-visual evoked potentials and pattern-reversal visual evoked potentials). No significant differences between medication-naïve and medication-experienced depressed subjects were found in terms of the neurobiological markers assessed, after controlling for age, sex, age at onset, number of depressive episodes, depression subtype (melancholic, atypical or undifferentiated) and severity of current episode. Unmedicated currently depressed patients, no matter their previous exposure to antidepressants, show similar changes in brain function. This does not necessarily mean that antidepressants do not have a long term effect on brain physiology, since not all patients relapse. However, it seems that those patients who relapse after stopping medication, seem to 'regress' to an 'as if never medicated' state, with regard to brain function. These findings might suggest that continuous maintenance treatment with antidepressants is essential for patients at high risk to relapse. Alternatively, they might suggest that our methodology assesses only a shallow and mainly state part of the pathophysiology of depression.

Electroretinographic assessment in major depressed patients receiving duloxetine: might differences between responders and non-responders indicate a differential biological background?

INTRODUCTION

Despite intense research efforts, still too little is known about the biological determinants of depression, thus soliciting diverse study approaches. Among others, the electroretinography (ERG) has been proposed even as a putative proxy (retinal) measurement of central dopaminergic activity for Major Depressive Disorder (MDD) both in drug-naïve patients and subjects receiving antidepressant treatments. Nonetheless, current evidences are merely preliminary, essentially considering just older classes of antidepressants, thus requiring confirmation studies even with newer agents as duloxetine.

METHOD

Twenty MDD subjects and 20 matched controls received duloxetine 60 mg/day for 12 weeks, being monitored both by standard ERG recording and by administration of the Hamilton scales for Depression and Anxiety and the Young Mania Rating Scale at baseline and week 12 (end of the study).

RESULTS

ERG mean rod b-wave amplitude significantly reduced from baseline to week 12 in those depressed subjects achieving final response (p=.024), decreasing from the highest rank values to the ones, substantially unmodified, seen among non-responders and controls.

LIMITATIONS

Small sample size and lack of multiple assessments.

CONCLUSIONS

At least some MDD patients responding to duloxetine might exhibit a peculiar ERG pattern, hypothetically indicating a specific biological background. If confirmed by larger-sampled studies, these results might shed further light in the understanding of the biological determinants of different subtypes of depression, ideally showing alternative patterns of response upon different treatment interventions.

Revisiting the Dexamethasone Suppression Test in unipolar major depression: an exploratory study

BACKGROUND

Important methodological questions still exist concerning the Dexamethasone Suppression Test (DST), including the possibility of a better way of interpreting it. The aim of the present study was to explore the feasibility of an alternative way of interpreting DST results.

METHODS

A total of 50 patients with major depression aged 41.0 +/- 11.4 years old participated in the study. Past and present suicide attempts were recorded. Psychometric assessment included the Hamilton Depression Rating Scale (HDRS), the Hamilton Anxiety Scale (HAS), the Newcastle Depression Diagnostic Scale (NDDS), the Diagnostic Melancholia Scale (DMS) and the General Assessment of Functioning (GAF) scale. The 1 mg DST protocol was used. Analysis methods included the chi square test and analysis of covariance (ANCOVA) with Fisher least significant difference (LSD) as post hoc tests.

RESULTS

In all, 34 patients (68%) were suppressors, 16 (32%) were non-suppressors and 14 patients had cortisol values above 5 microg/dl at baseline. Baseline cortisol level did not influence the classical DST interpretation. A total of 18 patients (36%) showed an increase of their cortisol levels after dexamethasone administration and 32 patients (64%) showed a decrease. Reducers had less melancholic features, similar levels of depression, better sleep and less suicidal thoughts in comparison to increasers. No relationship of DST to suicidality was found.

DISCUSSION

The present study explored the pattern of cortisol response to dexamethasone suppression and suggested an alternative way of coding and interpreting the DST on the basis of whether the cortisol levels remain stable or increase vs decrease after the administration of cortisol. The results put forward a complex way of understanding the relationship of the DST results with clinical symptoms.

Is it possible to predict the long-term response to venlafaxine with the use of biological markers and psychophysiological methods?

INTRODUCTION

The present study investigated whether it is possible to predict the medium term response to venlafaxine using biological markers and psychophysiological methods.

MATERIAL

Fourteen (14) patients aged 21-60 years suffering from Major Depression according to DSM-IV were included in the study.

METHODS

The SCAN v 2.0 and the IPDE were used to assist clinical diagnosis. Patients were investigated with electrooculogram (EOG), Pattern-Reversal Visual Evoked Potentials (PR-VEPs), Dexamethasone Suppression Test (DST), D-fenfluramine Challenge Test, and brain Single Photon Emission Tomography (SPECT). Venlafaxine 150-225 mg per os daily was administered. The follow-up period was 2 years.

STATISTICAL ANALYSIS

Chi-square test and ANOVA were used for the analysis of data.

RESULTS

There was a lower left globus pallidus regional cerebral blood flow in patients with better response. On the contrary, chronic patients were closer to normality.

DISCUSSION

The results of the current study provide preliminary evidence concerning our ability to predict response to venlafaxine and to understand its way of action.