The dexamethasone suppression test: its relationship to diagnoses, severity of depression and response to treatment

Is there a relationship between morphological and functional platelet changes and depressive disorder?

BACKGROUND

Blood platelets, due to shared biochemical and functional properties with presynaptic serotonergic neurons, constituted, over the years, an attractive peripheral biomarker of neuronal activity. Therefore, the literature strongly focused on the investigation of eventual structural and functional platelet abnormalities in neuropsychiatric disorders, particularly in depressive disorder. Given their impact in biological psychiatry, the goal of the present paper was to review and critically analyze studies exploring platelet activity, functionality, and morpho-structure in subjects with depressive disorder.

METHODS

According to the PRISMA guidelines, we performed a systematic review through the PubMed database up to March 2020 with the search terms: (1) platelets in depression [Title/Abstract]"; (2) "(platelets[Title]) AND depressive disorder[Title/Abstract]"; (3) "(Platelet[Title]) AND major depressive disorder[Title]"; (4) (platelets[Title]) AND depressed[Title]"; (5) (platelets[Title]) AND depressive episode[Title]"; (6) (platelets[Title]) AND major depression[Title]"; (7) platelet activation in depression[All fields]"; and (8) platelet reactivity in depression[All fields]."

RESULTS

After a detailed screening analysis and the application of specific selection criteria, we included in our review a total of 106 for qualitative synthesis. The studies were classified into various subparagraphs according to platelet characteristics analyzed: serotonergic system (5-HT2A receptors, SERT activity, and 5-HT content), adrenergic system, MAO activity, biomarkers of activation, responsivity, morphological changes, and other molecular pathways.

CONCLUSIONS

Despite the large amount of the literature examined, nonunivocal and, occasionally, conflicting results emerged. However, the findings on structural and metabolic alterations, modifications in the expression of specific proteins, changes in the aggregability, or in the responsivity to different pro-activating stimuli, may be suggestive of potential platelet dysfunctions in depressed subjects, which would result in a kind of hyperreactive state. This condition could potentially lead to an increased cardiovascular risk. In line with this hypothesis, we speculated that antidepressant treatments would seem to reduce this hyperreactivity while representing a potential tool for reducing cardiovascular risk in depressed patients and, maybe, in other neuropsychiatric conditions. However, the problem of the specificity of platelet biomarkers is still at issue and would deserve to be deepened in future studies.

Cortisol Stress Response and in Vivo PET Imaging of Human Brain Serotonin 1A Receptor Binding

BACKGROUND

Abnormalities in the hypothalamic-pituitary-adrenal axis, serotonergic system, and stress response have been linked to the pathogenesis of major depressive disorder. State-dependent hyper-reactivity of the hypothalamic-pituitary-adrenal axis is seen in major depressive disorder, and higher binding to the serotonin 1A receptor is observed as a trait in both currently depressed and remitted untreated major depressive disorder. Here, we sought to examine whether a relationship exists between cortisol secretion in response to a stressor and serotonin 1A receptor binding throughout the brain, both in healthy controls and participants with major depressive disorder.

METHODS

Research participants included 42 medication-free, depressed subjects and 31 healthy volunteers. Participants were exposed to either an acute, physical stressor (radial artery catheter insertion) or a psychological stressor (Trier Social Stress Test). Levels of serotonin 1A receptor binding on positron emission tomography with [11C]WAY-100635 were also obtained from all participants. The relationship between [11C]WAY-100635 binding and cortisol was examined using mixed linear effects models with group (major depressive disorder vs control), cortisol, brain region, and their interactions as fixed effects and subject as a random effect.

RESULTS

We found a positive correlation between post-stress cortisol measures and serotonin 1A receptor ligand binding levels across multiple cortical and subcortical regions, independent of diagnosis and with both types of stress. The relationship between [11C]WAY-100635 binding and cortisol was homogenous across all a priori brain regions. In contrast, resting cortisol levels were negatively correlated with serotonin 1A receptor ligand binding levels independently of diagnosis, except in the RN. There was no significant difference in cortisol between major depressive disorder participants and healthy volunteers with either stressor. Similarly, there was no correlation between cortisol and depression severity in either stressor group.

CONCLUSIONS

This study suggests that there may be a common underlying mechanism that links abnormalities in the serotonin system and hypothalamic-pituitary-adrenal axis hyper-reactivity to stress. Future studies need to determine how hypothalamic-pituitary-adrenal axis dysfunction affects mood to increase the risk of suicide in major depression.

Combined dexamethasone suppression-corticotrophin-releasing hormone stimulation test in medication-free major depression and healthy volunteers

BACKGROUND

The hypothalamic-pituitary-adrenal (HPA) axis is dysfunctional in a subgroup of mood disorders.

METHODS

We compared cortisol and adrenocorticotropic hormone (ACTH) responses in major depression and healthy volunteers to the combined dexamethasone suppression-corticotrophin-releasing hormone stimulation (DEX-CRH) test. Unlike other published studies, the study patients were medication-free and the healthy volunteers did not have first-degree relatives with a mood or psychotic disorder. Demographics, DSM-IV diagnoses and other clinical parameters were evaluated in major depressive disorder (MDD) and healthy control groups. Participants received an oral dose of 1.5mg dexamethasone at 11 pm the day before CRH administration. On the following day, at 3 pm, 100 µg of ovine CRH was infused. Blood samples for determination of cortisol and ACTH were collected every 15 min from 3 pm to 4:15 pm. Cortisol and ACTH responses were calculated as areas under the curve.

RESULTS

Controlling for age, baseline (i.e., post-dexamethasone) ACTH levels were higher in depressed patients compared to controls (p=0.01). There was a trend for higher ACTH responses in depressed patients compared to the control group (p=0.08). In depressed patients, cortisol and ACTH responses correlated positively with age, duration of illness and number of hospitalizations.

LIMITATIONS

Because of the cross-sectional study design we can only evaluate the nature of potential HPA axis disturbances that were present in patients when they are acutely depressed.

CONCLUSIONS

Feedback inhibition of ACTH secretion by cortisol is compromised in MDD, and this is independent of an age effect on the HPA axis function.

Corticosterone facilitates fluoxetine-induced neuronal plasticity in the hippocampus

The hippocampal dentate gyrus has been implicated in a neuronal basis of antidepressant action. We have recently shown a distinct form of neuronal plasticity induced by the serotonergic antidepressant fluoxetine, that is, a reversal of maturation of the dentate granule cells in adult mice. This “dematuration” is induced in a large population of dentate neurons and maintained for at least one month after withdrawal of fluoxetine, suggesting long-lasting strong influence of dematuration on brain functioning. However, reliable induction of dematuration required doses of fluoxetine higher than suggested optimal doses for mice (10 to 18 mg/kg/day), which casts doubt on the clinical relevance of this effect. Since our previous studies were performed in naive mice, in the present study, we reexamined effects of fluoxetine using mice treated with chronic corticosterone that model neuroendocrine pathophysiology associated with depression. In corticosterone-treated mice, fluoxetine at 10 mg/kg/day downregulated expression of mature granule cell markers and attenuated strong frequency facilitation at the synapse formed by the granule cell axon mossy fiber, suggesting the induction of granule cell dematuration. In addition, fluoxetine caused marked enhancement of dopaminergic modulation at the mossy fiber synapse. In vehicle-treated mice, however, fluoxetine at this dose had no significant effects. The plasma level of fluoxetine was comparable to that in patients taking chronic fluoxetine, and corticosterone did not affect it. These results indicate that corticosterone facilitates fluoxetine-induced plastic changes in the dentate granule cells. Our finding may provide insight into neuronal mechanisms underlying enhanced responsiveness to antidepressant medication in certain pathological conditions.

Melancholia in Latin American studies: a distinct mood disorder for the ICD-11

OBJECTIVE

Melancholic depression is a lifetime diagnosis, typically with recurrent episodes. Melancholia, a syndrome with a long history and distinctive psychopathological features, is differentiated from major depression by the DSM-IV specifiers and partly described in the International Classification of Diseases - 10th edition. Within the present classification, it is frequently seen in severely ill patients with major depression and bipolar disorder. Nevertheless, it has a distinctive psychopathology and biological homogeneity in clinical experience and laboratory test markers, and it is differentially responsive to specific treatment interventions according to international studies. The objective of this study is to review the literature published by Latin American authors about Melancholia.

METHOD

We conducted a systematic search to identify scientific literature published by Latin American authors gathering information relevant to the revision of the classification of mental and behavioral disorders in patients with melancholic depression of the International Classification of Diseases - 10th edition. The review was specifically focused on literature from Brazil and Latin America in order to examine the specific Latin American contribution for the study of melancholia as a distinct entity.

RESULTS AND CONCLUSION

Melancholia can be identified as a separate mood disorder with unique psychopathology and psychoneuroendocrinology, worthy of separate attention in the classification systems. We therefore suggest that melancholia be positioned as a distinct, identifiable mood disorder that requires specific treatment.

Salivary cortisol is associated with diagnosis and severity of late-life generalized anxiety disorder

Age-associated alterations in hypothalamic-pituitary-adrenal (HPA) axis functioning may make individuals more susceptible to HPA dysregulation in the context of mood and anxiety disorders. Little to no research has been done to examine HPA axis function in generalized anxiety disorder (GAD), particularly in late-life GAD, the most prevalent anxiety disorder in the elderly. The study sample consisted of 71 GAD subjects and 40 nonanxious comparison subjects over 60 years of age. We examined the hypotheses that elderly individuals with GAD will have elevated salivary cortisol levels compared to nonanxious subjects, and that elevated cortisol levels in GAD will be associated with measures of symptom severity. We report that late-life GAD is characterized by elevated basal salivary cortisol levels, with higher peak cortisol levels and larger areas under the curve, compared to nonanxious subjects. Additionally, severity of GAD as measured by the GAD Severity Scale and the Penn State Worry Questionnaire are positively correlated with cortisol levels. These data demonstrate HPA axis dysfunction in late-life GAD and suggest the need for additional research on the influence of aging on HPA axis function in mood and anxiety disorders.

Repeated paroxetine treatment reverses anhedonia induced in rats by chronic mild stress or dexamethasone

The present study was designed to assess the effect of dexamethasone, a synthetic glucocorticoid receptor agonist, in the sucrose preference test in rats. Rats treated acutely with dexamethasone (5-10 mg/kg) showed a significant decrease in sucrose preference (anhedonia) in comparison to vehicle treated rats, although 1 mg/kg dexamethasone did not alter the sucrose preference. Daily paroxetine treatment (10 g/kg, i.p., 14 days) reversed the anhedonic effect of acute dexamethasone (5 mg/kg), while causing no increased sucrose preference in rats that received dexamethasone vehicle. The paroxetine vehicle treated rats showed anhedonia even 14 days after acute dexamethasone administration. Paroxetine (10 mk/kg, i.p. for 28 days) also reversed anhedonia induced by chronic mild stress (8 weeks). In conclusion, acute dexamethasone induced an enduring anhedonic state that was reversed by repeated paroxetine treatment. Thus, the present study adds new data to the evidence supporting an important role for glucocorticoid in depression.

Effect of comorbid anxiety disorders on the hypothalamic-pituitary-adrenal axis response to a social stressor in major depression

BACKGROUND

Major depressive disorder (MDD) is often complicated by anxiety symptoms, and anxiety disorders occur in approximately 30% of mood cases. This study examined the influence of anxiety comorbidity on the hypothalamic-pituitary-adrenal (HPA) axis response to stress in patients with MDD.

METHODS

Untreated subjects with pure MDD (n = 15), MDD with comorbid anxiety disorders (n = 18), and pure anxiety disorders (n = 15) were recruited by advertising. Age- and gender-matched control subjects were recruited for each subject with a psychiatric diagnosis (n = 48). All subjects underwent a social stressor, the Trier Social Stress Test (TSST), and blood was collected for adrenocorticotropic hormone (ACTH) and cortisol assay.

RESULTS

When all depressed patients (n = 33) were compared with their matched control subjects (n = 33), they showed a significantly greater ACTH response to the stressor; however, this exaggerated ACTH response was exclusively due to the depressed group with comorbid anxiety disorders. A similar but nonsignificant effect was observed in the cortisol response. Subjects with pure mood or pure anxiety disorders showed normal ACTH and cortisol responses to the TSST. All patient groups showed similar levels of TSST-induced anxiety.

CONCLUSIONS

Comorbid anxiety disorders might play a role in the increased activation of the HPA axis observed in patients with major depression.

Depressed patients have higher body temperature: 5-HT transporter long promoter region effects

BACKGROUND

Depression has been associated with a decrease in intracellular serotonin (5-HT) reuptake through its transporter, SERT. The 5-HT transporter long promoter region (5-HTTLPR) deletion in the SERT gene has also been associated with a decrease in 5-HT reuptake. Conversely, increases in extracellular 5-HT have been associated with increased temperature. It has not been established, however, whether body temperature in depressed patients is different from controls. Here, we hypothesized that temperature would be increased in depressed patients as well as in those with the 5-HTTLPR deletion.

METHODS

A strict oral temperature protocol employed single, cross-sectional, naturalistic time-of-day temperature measures in 125 subjects (46 normal controls, 79 outpatients with major depression). Controls and depressed patients were free of psychotropic medication and classified by the Structured Clinical Interview for Psychiatric Diagnoses. Eighty-one of the subjects (68 depressed, 13 normal) were additionally genotyped for 5-HTTLPR polymorphisms.

RESULTS

Depressed patients had a significantly higher uncorrected body temperature (mean +/- SD 98.38 +/- 0.61 degrees F) than controls (mean +/- SD 98.13 +/- 0.59 degrees F; F = 4.8, p = 0.03). An age (F = 14.09, p < 0.001) and time-of-day (11.4, p = 0.001) correction revealed a more robust (F = 14.02, p < 0.001) difference between depressed patients (mean +/- SD 98.44 +/- 0.55 degrees F) and controls (mean +/- SD 98.02 +/- 0.56 degrees F). When normalized for age and circadian differences between subjects, random, outpatient oral temperatures had a sensitivity of 63% and a specificity of 76% in identifying the depressed subjects from the controls. Independent of depression, subjects with the 5-HTTLPR deletion (short SERT allele) were warmer (mean +/- SD 98.33 +/- 0.65 degrees F) than those lacking the short allele on either chromosome (mean +/- SD 97.91 +/- 0.69 degrees F; F = 7.0, p = 0.01). However, the genotype did not explain the temperature differences between controls and depressed patients.

CONCLUSION

This is the first demonstration of an increased daytime body temperature in cases with major depression. Subjects with a corrected temperature above 98.3 degrees F were 2.6-fold more likely to be depressed. The results may strengthen the hypothesis of an inflammatory component of depression. In addition, the findings suggest a potential link between genetic differences in 5-HT transport and body temperature.

The central mechanism of hypothalamic-pituitary-adrenocortical system hyperfunction in depressed patients

While hypercortisolemia is commonly observed in depression, exactly where in the hypothalamic-pituitary-adrenocortical (H-P-A) axis this dysfunction arises remains undefined. In attempting to distinguish between central or peripheral locus of dysfunction, we studied in 12 patients (10 females, two males) with primary major depression and eight age-matched controls (six females, two males) in their adrenal cortisol response to infused adrenocorticotropic hormone (ACTH) (cosyntropin 0.05 microg/kg bodyweight) while endogenous ACTH was suppressed with 1 mg of dexamethasone. Compared with the control group, pre-dexamethasone plasma baseline cortisol level was significantly higher in depressed patients while ACTH level remained normal. Post-dexamethasone responses of both hormones were greatly non-suppressed in the depressed group. Exogenous cosyntropin-elicited rise in plasma cortisol was significantly lower in depressed patients while the ACTH response was not significantly different. These findings suggest that an adrenal cortisol response to ACTH was significantly decreased during depression as compared with normals in Chinese depressed patients. Therefore, the central mechanism of hyperfunctioning H-P-A axis causing hypercortisolemia should be emphasized.