Fronto-limbic brain structures in suicidal and non-suicidal female patients with major depressive disorder

Reduced amygdala volume in newly admitted psychiatric in-patients with unipolar major depression

Structural neuroimaging studies investigating amygdala volumes in patients suffering from major depression have yielded variable results. Discrepant findings across studies may be attributable in part to heterogeneity with respect to antidepressant medication and to lack of adequate control for the effects of total brain volume and age. Here, 24 unipolar depressed in-patients newly admitted to a psychiatric unit and 14 healthy control participants matched for age, gender, and years of education underwent quantitative magnetic resonance imaging (MRI) toward the end of a one-week washout period. Saliva cortisol was measured at 08.00 and at 16.00h in patients during washout. Absolute amygdala volumes were significantly reduced in the patient group (by 13% in left amygdala and 12% in right amygdala). The effect of reduced amygdala volumes in patients remained significant after correction for brain volume (BV) and age. Furthermore, amygdala volume measurements in the patient sample showed a significant inverse relationship to the number of preceding depressive episodes. In patients, severity of disease (baseline HAMD scores) and baseline cortisol levels were not related to amygdala volume. This study of a sample of unmedicated depressed in-patients adds to the small, yet growing, body of evidence linking untreated major depression to reduced amygdala volume.

Structural brain abnormalities in major depressive disorder: a selective review of recent MRI studies

BACKGROUND

While there is evidence to suggest that major depressive disorder (MDD) is associated with structural brain abnormalities, the precise nature of these abnormalities remains unclear.

AIMS

To review recent structural magnetic resonance imaging (MRI) research findings in MDD while considering the potential influence of key clinical and demographic variables.

METHOD

A selective review of all T1-weighted structural MRI studies published between 2000 and 2007 in adult samples of MDD patients.

RESULTS

Volumetric reductions of the hippocampus, basal ganglia and OFC and SGPFC are consistently found in MDD patients, with more persistent forms of MDD (e.g., multiple episodes or repeated relapses, longer illness duration) being associated with greater impact on regional brain volumes. Gender, medication, stage of illness, and family history all affect the nature of the findings in a regionally specific manner.

LIMITATIONS

Overall, differences between the samples in factors such as illness severity, medication, gender and family history of mental illness makes difficult to identify their confounding effects on the observed neuroanatomical changes. Also, the tracing protocols used for particular brain regions were different amongst the reviewed studies, making difficult to compare their findings.

CONCLUSIONS

The data support the notion that MDD involves pathological alterations of limbic and cortical structures, and that they are generally more apparent in patients with more severe or persistent forms of the illness.

Through the looking glass: examining neuroanatomical evidence for cellular alterations in major depression

Alterations in brain plasticity are increasingly thought to play important roles in major depressive disorder (MDD) and suicide. To gain a better understanding of the gross structural changes observed in the brains of major depressed and suicide subjects, a number of recent investigations have scrutinized the cellular integrity of brain regions implicated in mood disorders. The purpose of this review is to summarize the current knowledge on the microscopic features of neuronal and glial cell populations in these different brain regions, namely the prefrontal cortex, hippocampus, amygdala, raphe nucleus and locus coeruleus. In general, evidence from this burgeoning field supports the hypothesis of altered cell plasticity in MDD and suicide occurring mainly in key fronto-limbic areas. Interestingly, reported morphometric and cell density alterations are generally region-specific and implicate several neuromodulatory systems, notably GABAergic, serotonergic, noradrenergic and glutamatergic pathways. Cell-specific changes involve reductions in densities of astrocytes and oligodendrocytes, while increases in microglial densities have also been reported. Furthermore, increases in neuronal densities have been found in subcortical regions. The implication of such findings for our understanding of the cellular and molecular underpinnings of MDD and suicide are discussed, and the strengths and weaknesses of morphological approaches used to analyse human postmortem brain tissues are evaluated.

A voxel-based morphometry study of frontal gray matter correlates of impulsivity

Impulsivity is a personality trait exhibited by healthy individuals, but excessive impulsivity is associated with some mental disorders. Lesion and functional neuroimaging studies indicate that the ventromedial prefrontal region (VMPFC), including the orbitofrontal cortex (OFC), anterior cingulate cortex (ACC) and medial prefrontal cortex, and the amygdala may modulate impulsivity and aggression. However, no morphometric study has examined the association between VMPFC and impulsivity. We hypothesized that healthy subjects with high impulsivity would have smaller volumes in these brain regions compared with those with low impulsivity. Sixty-two healthy subjects were studied (age 35.4 +/- 12.1 years) using a 1.5-T MRI system. The Barratt impulsiveness scale (BIS) was used to assess impulsivity. Images were processed using an optimized voxel-based morphometry (VBM) protocol. We calculated the correlations between BIS scale scores and the gray matter (GM) and white matter (WM) volumes of VMPFC and amygdala. GM volumes of the left and right OFC were inversely correlated with the BIS total score (P = 0.04 and 0.02, respectively). Left ACC GM volumes had a tendency to be inversely correlated with the BIS total score (P = 0.05). Right OFC GM volumes were inversely correlated with BIS nonplanning impulsivity, and left OFC GM volumes were inversely correlated with motor impulsivity. There were no significant WM volume correlations with impulsivity. The results of this morphometry study indicate that small OFC volume relate to high impulsivity and extend the prior finding that the VMPFC is involved in the circuit modulating impulsivity.

Amygdala volumes in mood disorders--meta-analysis of magnetic resonance volumetry studies

BACKGROUND

The amygdala plays an important role in the regulation of emotions and has been implicated in the pathophysiology of mood disorders. Studies of amygdala volumes in mood disorders have been conflicting, with findings of increased, decreased and unchanged amygdala volumes in patients relative to controls. We present the largest meta-analysis of amygdala volumes in mood disorders and the first one to investigate modifying effects of clinical, demographic and methodological variables.

METHODS

We reviewed 40 magnetic resonance imaging studies investigating amygdala volumes in patients with unipolar or bipolar disorders. For meta-analysis we used standardized differences in means (SDM) and random effect models. In the search for sources of heterogeneity, we subdivided the studies based on diagnosis, setting, age, medication status, sex, duration of illness, slice thickness, interrater reliability of tracing and anatomical definitions used.

RESULTS

The volumes of the left and right amygdala in bipolar (N=215) or unipolar (N=409) patients were comparable to controls. Bipolar children and adolescents had significantly smaller left amygdala volumes relative to controls (SDM=-0.34, 95%CI=-0.65; -0.04, z=-2.20, p=0.03), whereas bipolar adults showed a trend for left amygdala volume increases (SDM=0.46, 95%CI=-0.03; 0.96, z=1.83, p=0.07). Unipolar inpatients had significantly larger left (SDM=0.35, 95%CI=0.03; 0.67, z=-2.17, p=0.03) amygdala volumes than controls, with no significant amygdala volume changes in unipolar outpatients.

LIMITATIONS

Heterogeneity of included studies.

CONCLUSIONS

The absence of overall differences in amygdala volumes, in the presence of significant and sometimes mirror changes in patient subgroups, demonstrates marked heterogeneity among mood disorders. Amygdala volume abnormalities may not be associated with mood disorders per se, but rather may underlie only some dimensions of illness or represent artifacts of medication or comorbid conditions.

Inferior frontal white matter volume and suicidality in schizophrenia

The neurobiology of suicidality in schizophrenia is largely unknown. We therefore assessed gray and white matter volumes associated with past suicidality and current self-aggression in schizophrenia. Fifty-five outpatients with schizophrenia (n=55) and healthy controls (n=55), matched for age, gender and handedness, were recruited. Ten patients had a life-time history of one or more suicide attempts. Current self-aggression was assessed using the Modified Overt Aggression Scale. High resolution structural magnetic resonance images were analyzed by voxel-based morphometry. We found significantly larger inferior frontal white matter volumes bilaterally in patients with a previous suicide attempt as compared with those patients without a history of suicidality. No other significant white or gray matter volume differences were observed. White matter volume in these regions did not differ between healthy controls and those patients without a previous suicide attempt. Furthermore, among patients, the level of current self-aggression showed a significant positive correlation with white matter volume in the same regions. Inferior frontal white matter alterations in fronto-temporo-limbic circuits may be associated with suicidality and self-aggression in schizophrenia.

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

Major depressive disorder has been associated with volumetric abnormality in the amygdala. In this meta-analysis we examine results from magnetic resonance imaging volumetry studies of the amygdala in depression in order to assess both the nature of the relationship between depression and amygdala volume as well as the influence of extraexperimental factors that may account for significant variability in reported findings. We searched PubMed and ISI Web of Knowledge databases for articles published from 1985 to 2008 that used the wildcard terms 'Depress*' and 'Amygdal*' in the title, keywords or abstract. From the 13 studies that met inclusion criteria for our meta-analysis, we calculated aggregate effect size and heterogeneity estimates from amygdala volumetric data; we then used meta-regression to determine whether variability in specific extraexperimental factors accounted for variability in findings. The lack of a reliable difference in amygdala volume between depressed and never-depressed individuals was accounted for by a positive correlation between amygdala volume differences and the proportion of medicated depressed persons in study samples: whereas the aggregate effect size calculated from studies that included only medicated individuals indicated that amygdala volume was significantly increased in depressed relative to healthy persons, studies with only unmedicated depressed individuals showed a reliable decrease in amygdala volume in depression. These findings are consistent with a formulation in which an antidepressant-mediated increase in levels of brain-derived neurotrophic factor promotes neurogenesis and protects against glucocorticoid toxicity in the amygdala in medicated but not in unmedicated depression.

Left orbitofrontal and superior temporal gyrus structural changes associated to suicidal behavior in patients with schizophrenia

Suicidal attempts are relatively frequent and clinically relevant in patients with schizophrenia. Recent studies have found gray matter differences in suicidal and non-suicidal depressive patients. However, no previous neuroimaging study has investigated possible structural abnormalities associated to suicidal behaviors in patients with schizophrenia. A whole-brain magnetic resonance voxel-based morphometric examination was performed on 37 male patients meeting the DSM-IV criteria for schizophrenia. Thirteen (35.14%) patients had attempted suicide. A non-parametric permutation test was computed to perform the comparability between groups. An analysis of covariance (AnCova) model was constructed with a statistical threshold of p<0.05 corrected for multiple comparisons. After controlling for age and severity of illness, results showed significant gray matter density reduction in left superior temporal lobe (p=0.03) and left orbitofrontal cortex (p=0.04) in patients who had attempted suicide when comparing with non-suicidal patients. Although sample size limitations and potential clinical heterogeneity preclude definitive conclusions, these data point to structural differences in key cerebral areas. Neuroimaging studies are necessary to expand our knowledge of biological mechanisms underlying suicide in schizophrenia.

No pituitary gland volume change in medication-free depressed patients

Increased serum cortisol levels and a hyperactive hypothalamo-pituitary-adrenal (HPA) axis have been proposed to play an important role in the pathophysiology of Major Depressive Disorder (MDD). However, there are inconsistent results regarding pituitary gland volume (PGV), which is one of the key elements of the HPA axis evaluated by MRI in depressed patients. In this study, we analyzed the PGV of medication-free moderately depressed MDD patients (N=34) and age and sex matched healthy controls (N=39). PGV did not differ between MDD patients and healthy controls [mean volume+/-S.D.; 0.76+/-0.17 cm3 and 0.75+/-0.14 cm3; ANCOVA, F1,69=1.25 p>0.05; respectively]. Our results confirm that volumetric PGV changes are not crucial for depression pathophysiology among unmedicated, moderately depressed adults.

Association of limbic system-associated membrane protein (LSAMP) to male completed suicide

Background

Neuroimaging studies have demonstrated volumetric abnormalities in limbic structures of suicide victims. The morphological changes might be caused by some inherited neurodevelopmental defect, such as failure to form proper axonal connections due to genetically determined dysfunction of neurite guidance molecules. Limbic system-associated membrane protein (LSAMP) is a neuronal adhesive molecule, preferentially expressed in developing limbic system neuronal dendrites and somata. Some evidence for the association between LSAMP gene and behavior has come from both animal as well as human studies but further investigation is required. In current study, polymorphic loci in human LSAMP gene were examined in order to reveal any associations between genetic variation in LSAMP and suicidal behaviour.

Methods

DNA was obtained from 288 male suicide victims and 327 healthy male volunteers. Thirty SNPs from LSAMP gene and adjacent region were selected by Tagger algorithm implemented in Haploview 3.32. Genotyping was performed using the SNPlex™ (Applied Biosystems) platform. Data was analyzed by Genemapper 3.7, Haploview 3.32 and SPSS 13.0.

Results

Chi square test revealed four allelic variants (rs2918215, rs2918213, rs9874470 and rs4821129) located in the intronic region of the gene to be associated with suicide, major alleles being overrepresented in suicide group. However, the associations did not survive multiple correction test. Defining the haplotype blocks using confidence interval algorithm implemented in Haploview 3.32, we failed to detect any associated haplotypes.

Conclusion

Despite a considerable amount of investigation on the nature of suicidal behaviour, its aetiology and pathogenesis remain unknown. This study examined the variability in LSAMP gene in relation to completed suicide. Our results indicate that LSAMP might play a role in pathoaetiology of suicidal behaviour but further studies are needed to understand its exact contribution.

Inhibition of 5-HT neuron activity and induction of depressive-like behavior by high-frequency stimulation of the subthalamic nucleus

Bilateral, high-frequency stimulation (HFS) of the subthalamic nucleus (STN) is the surgical therapy of choice for movement disability in advanced Parkinson's disease (PD), but this procedure evokes debilitating psychiatric effects, including depressed mood, of unknown neural origin. Here, we report the unexpected finding that HFS of the STN inhibits midbrain 5-hydroxytryptamine (5-HT) neurons to evoke depression-related behavioral changes. We found that bilateral HFS of the STN consistently inhibited (40-50%) the firing rate of 5-HT neurons in the dorsal raphe nucleus of the rat, but not neighboring non-5-HT neurons. This effect was apparent at clinically relevant stimulation parameters (> or =100 Hz, > or =30 microA), was not elicited by HFS of either neighboring or remote structures to the STN, and was still present in rat models of PD. We also found that bilateral HFS of the STN evoked clear-cut, depressive-like behavior in a widely used experimental paradigm of depression (forced swim test), and this effect was also observed in a PD model. Importantly, the depressive-like behavior elicited by HFS of the STN was reversed by a selective 5-HT-enhancing antidepressant, thereby linking the behavioral change to decreased 5-HT neuronal activity. Overall, these findings link reduced 5-HT function to the psychiatric effects of HFS of the STN observed in PD patients and provide a rational basis for their clinical management. More generally, the powerful interaction between the STN and 5-HT system uncovered here offers insights into the high level of comorbidity of basal ganglia disease and mood disorder.

Replication test for association of the IL-1 receptor antagonist gene, IL1RN, with attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) has a strong genetic basis, and aberrant brain dopaminergic and noradrenergic activity is implicated in its etiology. Interleukin-1 (IL-1), its antagonist, IL-1Ra, and IL-1 receptors are all present in the brain, and IL-1 has been shown to influence both dopaminergic and noradrenergic function. Recently, Segman et al. [1] tested the IL-1Ra gene, IL1RN, as a candidate for involvement in ADHD. Using the transmission/disequilibrium test (TDT) to examine 77 nuclear ADHD families for the inheritance of alleles of an intronic 86-bp VNTR polymorphism, they found significant evidence for biased transmission of the 4-repeat allele (p=0.04) and non-transmission of the 2-repeat allele (p=0.03). Here, we sought to replicate this in an independent sample of families. In contrast to the previous findings, our analysis of 178 ADHD families showed no evidence for biased transmission of these alleles (p=0.81 and p=1.00, respectively). Our lack of evidence for association of this IL1RN polymorphism with ADHD, based on a much larger sample of families, suggests that the original finding may have been a spurious (i.e. false-positive) result. These findings highlight the need for further investigations of this marker, in additional independent ADHD samples, in the future.