Blood-based biomarkers predicting response to antidepressants

Many studies have explored the association between soluble interleukin-2 receptor (sIL-2R), cytokines and major depressive disorder (MDD). However, the results of these studies were not consistent. The aim of our study is to compare the levels of sIL-2R and cytokines in the blood between MDD patients and controls by a meta-analysis and to identify moderators accounting for potential heterogeneity in the levels of sIL-2R and cytokines in MDD patients versus controls by meta-regression analyses. A comprehensive literature search was performed to identify studies comparing the levels of sIL-2R and cytokines between MDD patients and controls. We pooled the effect sizes for standardized mean differences (SMD) of the levels of sIL-2R and cytokines. We also performed meta-regression and sensitivity analyses to investigate the roles of age, gender, sample type, ethnic origin and selected studies' quality in explaining potential heterogeneity and differences in results respectively. Twenty-nine studies were selected for this analysis. The levels of sIL-2R, TNF-α and IL-6 in MDD patients were significantly higher than those of healthy controls (SMD=0.555, p<0.001, SMD=0.567, p=0.010; SMD=0.680, p<0.001). Mean age of all subjects was a significant moderator to explain the high heterogeneity of IL-6. Sensitivity analysis found that European but not non-European subjects have higher levels difference of sIL-2R, TNF-α and IL-1β between MDD patients and controls. The severity of MDD was not considered. The blood levels of sIL-2R, TNF-α and IL-6 were significantly higher in MDD patients than controls. Age, samples source and ethnic origins may play a potential role in heterogeneity. Copyright © 2011 Elsevier B.V. All rights reserved.

Several studies have reported antidepressant effects of anti-inflammatory treatment; however, the results have been conflicting and detrimental adverse effects may contraindicate the use of anti-inflammatory agents. To systematically review the antidepressant and possible adverse effects of anti-inflammatory interventions. Trials published prior to December, 31, 2013, were identified searching Cochrane Central Register of Controlled Trials, PubMed, EMBASE, PsychINFO, Clinicaltrials.gov, and relevant review articles. Randomized placebo-controlled trials assessing the efficacy and adverse effects of pharmacologic anti-inflammatory treatment in adults with depressive symptoms, including those who fulfilled the criteria for depression. Data were extracted by 2 independent reviewers. Pooled standard mean difference (SMD) and odds ratios (ORs) were calculated. Depression scores after treatment and adverse effects. Ten publications reporting on 14 trials (6262 participants) were included: 10 trials evaluated the use of nonsteroidal anti-inflammatory drugs (NSAIDs) (n=4,258) and 4 investigated cytokine inhibitors (n=2,004). The pooled effect estimate suggested that anti-inflammatory treatment reduced depressive symptoms (SMD, -0.34; 95% CI, -0.57 to -0.11; I2=90%) compared with placebo. This effect was observed in studies including patients with depression (SMD, -0.54; 95% CI, -1.08 to -0.01; I2=68%) and depressive symptoms (SMD, -0.27; 95% CI, -0.53 to -0.01; I2=68%). The heterogeneity of the studies was not explained by differences in inclusion of clinical depression vs depressive symptoms or use of NSAIDs vs cytokine inhibitors. Subanalyses emphasized the antidepressant properties of the selective cyclooxygenase 2 inhibitor celecoxib (SMD, -0.29; 95% CI, -0.49 to -0.08; I2=73%) on remission (OR, 7.89; 95% CI, 2.94 to 21.17; I2=0%) and response (OR, 6.59; 95% CI, 2.24 to 19.42; I2=0%). Among the 6 studies reporting on adverse effects, we found no evidence of an increased number of gastrointestinal or cardiovascular events after 6 weeks or infections after 12 weeks of anti-inflammatory treatment compared with placebo. All trials were associated with a high risk of bias owing to potentially compromised internal validity. Our analysis suggests that anti-inflammatory treatment, in particular celecoxib, decreases depressive symptoms without increased risks of adverse effects. However, a high risk of bias and high heterogeneity made the mean estimate uncertain. This study supports a proof-of-concept concerning the use of anti-inflammatory treatment in depression. Identification of subgroups that could benefit from such treatment might be warranted.

Serum levels of inflammatory cytokines, for example, tumor necrosis factor alpha (TNFα), interleukin-6 (IL-6), and IL-1 beta (IL-1β), are elevated in subjects with major depressive disorder (MDD). The reason why this occurs is unclear. Elevated levels of inflammatory cytokines could be a result of brain dysfunction in MDD. It is also possible that inflammatory cytokines contribute to depressive symptoms in MDD. If the first assumption is correct, one would expect levels to normalize with resolution of the depressive episode after treatment. Several studies have measured changes in cytokine levels during antidepressant treatment; however, the results vary. The purpose of this study was to pool all available data on changes in serum levels of TNFα, IL-6, and IL-1β during antidepressant treatment to determine whether these levels change. Studies were included if they used an approved pharmacological treatment for depression, patients had a diagnosis of MDD, and serum levels of TNFα, IL-6, and/or IL-1β were measured before and after treatment. Twenty-two studies fulfilled these criteria. Meta-analysis of these studies showed that, overall, while pharmacological antidepressant treatment reduced depressive symptoms, it did not reduce serum levels of TNFα. On the other hand, antidepressant treatment did reduce levels of IL-1β and possibly those of IL-6. Stratified subgroup analysis by class of antidepressant indicated that serotonin reuptake inhibitors may reduce levels of IL-6 and TNFα. Other antidepressants, while efficacious for depressive symptoms, did not appear to reduce cytokine levels. These results argue against the notion that resolution of a depressive episode is associated with normalization of levels of circulating inflammatory cytokines; however, the results are consistent with the possibility that inflammatory cytokines contribute to depressive symptoms and that antidepressants block the effects of inflammatory cytokines on the brain.