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Major depressive disorder (MDD) is a common illness accompanied by considerable morbidity, mortality, costs, and heightened risk of suicide. We conducted a genome-wide association meta-analysis based in 135,458 cases and 344,901 controls and identified 44 independent and significant loci. The genetic findings were associated with clinical features of major depression and implicated brain regions exhibiting anatomical differences in cases. Targets of antidepressant medications and genes involved in gene splicing were enriched for smaller association signal. We found important relationships of genetic risk for major depression with educational attainment, body mass, and schizophrenia: lower educational attainment and higher body mass were putatively causal, whereas major depression and schizophrenia reflected a partly shared biological etiology. All humans carry lesser or greater numbers of genetic risk factors for major depression. These findings help refine the basis of major depression and imply that a continuous measure of risk underlies the clinical phenotype.

Importance: Antagonism of the postsynaptic metabotropic glutamate subtype 5 receptor is a novel approach to modulate glutamatergic function and has proven efficacy in a number of preclinical behavioral models of depression., Objective: To evaluate the safety and efficacy of basimglurant modified-release (MR) vs placebo as adjunctive therapy to ongoing antidepressant medication therapy in patients with MDD who had inadequate response within the current episode., Design, Setting, and Participants: In this phase 2b, double blind, randomized clinical trial of 333 adult patients with a DSM-IV-TR diagnosis of MDD across 59 research clinics globally, patients were assigned to 1 of 2 doses of basimglurant MR (0.5 or 1.5 mg) or placebo once daily, adjunctive to ongoing antidepressant medication therapy (selective serotonin reuptake inhibitor or serotonin and norepinephrine reuptake inhibitor). Patients were enrolled from October 5, 2011, through July 26, 2013., Interventions: Six-week treatment with 0.5 mg of basimglurant MR, 1.5-mg basimglurant MR, or placebo once daily, adjunctive to ongoing antidepressant medication therapy., Main Outcomes and Measures: The primary end point was the mean change from baseline score on the Montgomery-Åsberg Depression Rating Scale (MADRS), as rated by the clinician at week 6. Other measures included patient-rated MADRS, Quick Inventory of Depressive Symptomatology-Self-Report, Clinical Global Impression-Improvement, Patient Global Impression-Improvement, and Clinical Global Impression-Severity Scales and adverse events., Results: A total of 596 patients were screened, and 333 were randomized into the study (mean [SD] age, 47 [11.2] years; 216 female [65.1%]). The primary end point (mean change in clinician-rated MADRS score from baseline to end of treatment) was not met (effect size [ES] = 0.16, P = .42; intent-to-treat [ITT] mixed-effects model for repeated measures [MMRM] analysis for comparing 1.5-mg basimglurant MR and placebo). Across secondary and exploratory end points, 1.5-mg basimglurant MR revealed larger improvements vs placebo on the patient-rated MADRS (-16.2 vs -13.3, ES = 0.28, nominal P = .04), Quick Inventory of Depressive Symptomatology-Self-Report (-7.5 vs -5.8; ES = 0.37, nominal P = .009), Clinical Global Impression-Improvement mean score, and Patient Global Impression-Improvement mean score. Improvements were also seen in the patient-rated MADRS remission rate (36.0% vs 22.0%; nominal P = .03) and response rate (50.5% vs 40.4%; nominal P = .13), A 0.5-mg dose of basimglurant MR had no benefit over placebo in any of these measures. The most common adverse event was dizziness, which was mostly transient and of mild intensity., Conclusions and Relevance: No difference was observed on the study's primary outcome measure, the clinician-rated MADRS change from baseline to end of treatment, between adjunctive basimglurant MR vs placebo. Adjunctive 1.5-mg basimglurant MR daily revealed, however, an antidepressant effect across secondary end points, particularly in patient-rated measures. These findings combined with good tolerability warrant further investigation with this compound in depressive disorders., Trial Registration: clinicaltrials.gov Identifier: NCT01437657.

Objective: This study was designed to assess possible antidepressant effects of memantine, a selective N-methyl-D-aspartate (NMDA) receptor antagonist in humans., Method: In a double-blind, placebo-controlled study, 32 subjects with major depression were randomly assigned to receive memantine (5-20 mg/day) (N=16) or placebo (N=16) for 8 weeks. Primary efficacy was assessed by performance on the Montgomery-Asberg Depression Rating Scale (MADRS)., Results: The linear mixed models for total MADRS scores showed no treatment effect., Conclusions: In an 8-week trial, the low-to-moderate-affinity NMDA antagonist memantine in doses of 5-20 mg/day was not effective in the treatment of major depressive disorder.

There is growing evidence from neuroimaging and ostmortem studies that severe mood disorders, which have traditionally been conceptualized as neurochemical disorders, are associated with impairments of structural plasticity and cellular resilience. It is thus noteworthy that recent preclinical studies have shown that critical molecules in neurotrophic signaling cascades (most notably cyclic adenosine monophosphate [cAMP] response element binding protein, brain-derived neurotrophic factor, bcl-2, and mitogen activated protein [MAP] kinases) are long-term targets for antidepressant agents and antidepressant potentiating modalities. This suggests that effective treatments provide both trophic and neurochemical support, which serves to enhance and maintainnormal synaptic connectivity, thereby allowing the chemical signal to reinstate the optimal functioning of critical circuits necessary for normal affective functioning. For many refractory patients, drugs mimicking "traditional" strategies, which directly or indirectly alter monoaminergic levels, may be of limited benefit. Newer "plasticity enhancing" strategies that may have utility in the treatment of refractory depression include N-methyl-D-aspartate antagonists, alpha-amino-3-hydroxy-5-methylisoxazole propionate (AMPA) potentiators, cAMP phosphodiesterase inhibitors, and glucocorticoid receptor antagonists. Small-molecule agents that regulate the activity f growth factors, MAP kinases cascades, and the bcl-2 family of proteins are also promising future avenues. The development of novel, nonaminergic-based therapeutics holds much promise for improved treatment of severe, refractory mood disorders., (Copyright 2003 Society of Biological Psychiatry)