Systematic Review and Meta-Analysis: Dose-Response Relationship of Selective Serotonin Reuptake Inhibitors in Major Depressive Disorder

Meta-analysis: Risk of hyperhidrosis with second-generation antidepressants

BACKGROUND

Our goal was to quantify the risk of hyperhidrosis associated with commonly used antidepressant agents and examine the impact of medication class, pharmacodynamics, and dose on risk of hyperhidrosis.

METHODS

We conducted a PubMed search to identify all double-blind, randomized, placebo-controlled trials examining the efficacy of second-generation antidepressant medications in the treatment of adults with a depressive disorder, anxiety disorders, or obsessive-compulsive disorder. We used a random-effects meta-analysis to examine the pooled risk ratio of hyperhidrosis reported as a side effect in adults treated with second-generation antidepressants compared to placebo. We used stratified subgroup analysis and metaregression to examine the effects of medication type, class, dosage, indication, and receptor affinity profile on the measured risk of hyperhidrosis.

RESULTS

We identified 76 trials involving 28,544 subjects. There was no significant difference in the risk of hyperhidrosis between serotonin-norepinephrine reuptake inhibitors (SNRI) [risk ratio (RR) = 3.17, 95% CI: 2.63-3.82] and selective serotonin reuptake inhibitors (SSRI) (RR = 2.93, 95% CI: 2.46-3.47) medications compared to placebo. All antidepressant medications were associated with a significantly increased risk of hyperhidrosis except fluvoxamine (RR = 0.56, 95% CI: 0.12-2.53), bupropion (RR = 1.23, 95% CI: 0.57-2.67), and vortioxetine (RR = 1.35, 95% CI: 0.79-2.33). The dose of SSRI/SNRI medications was not significantly associated with the risk of hyperhidrosis. Increased risk of hyperhidrosis was associated with increased affinity of SSRI/SNRI medications to the dopamine transporter.

CONCLUSION

Risk of hyperhidrosis was significantly increased with most antidepressant medications but was associated with dopamine transporter affinity.

Escitalopram plasma levels and antidepressant response

Major Depression Disorder (MDD) has a highly variable treatment response due to the large inter-individual variation in the pharmacokinetics and pharmacodynamics of drug treatments. In detail the correlation between plasma level and efficacy has been much debated. Among first-line drugs for MDD, one of the most used is escitalopram. In the present study we investigated the association between serum concentration of escitalopram (SCE) and antidepressant response (AR). 70 MDD patients treated with escitalopram monotherapy were recruited and followed for three months. Hamilton Depression Rating Scale - 21 (HAMD-21) was administrated at baseline, month 1, and month 3 to assess AR. SCE was measured at steady state. Linear regression analysis and nonlinear least-squares regression were used to estimate association between SCE and AR. We found an association between SCE and AR both at month 1 (p<0.001) and month 3 (p=0.0003), which persists also excluding 3 patients with SCE equal to 0. Interestingly, by excluding patients with SCE < 20ng/mL, i.e. with a SCE lower than the putative therapeutic threshold, these associations disappeared. The curvilinear function AR = a + (SCE-SCE²) explained a higher proportion of variance compared to the linear other models (p<0.001). Our results suggest that for escitalopram the association between SCE and AR likely follows a nearly-asymptotic function, with poor AR at sub-therapeutic SCE and stable AR response at therapeutic SCE. Thus, when a patient reaches the therapeutic SCE range, further increase of escitalopram dosage seems to be useless, although further studies are needed to confirm our findings.

Pharmacological treatment of unipolar depressive disorders: summary of WFSBP guidelines

OBJECTIVE

Major depressive disorder (MDD) is a severe mood disorder affecting individuals of all ages and is characterised by single or recurrent major depressive episodes. Key elements of acute and maintenance treatment of MDD include pharmacotherapy, and psychological approaches such as psychoeducation and adherence monitoring.

METHODS

This summary of the 'Practice guidelines for the biological treatment of unipolar depressive disorders' comprises acute, continuation and maintenance treatment developed by an international Task Force of the World Federation of Societies of Biological Psychiatry (WFSBP), and focuses on pharmacological treatment options.

RESULTS

A variety of different antidepressants are available for the effective acute and prophylactic treatment of depressed patients. Randomised placebo-controlled efficacy studies indicate that all major classes of antidepressants are effective in acute treatment but also in preventing recurrence of depression showing about a two-fold higher relapse rate with placebo treatment. Evidence suggests that the 'newer' antidepressants have superior long-term effectiveness due to better tolerability and safety profile compared to traditional antidepressants, e.g., the tricyclic antidepressants (TCA).

CONCLUSIONS

Despite progress in the availability of different treatment options there is still a substantial proportion of patients who do not achieve full remission. Several add-on pharmacological treatment options are among the best-evidenced strategies for refractory depressed patients.

A Randomized Controlled Trial of Medication and Cognitive-Behavioral Therapy for Hypochondriasis

OBJECTIVE

Prior studies of hypochondriasis demonstrated benefits for pharmacotherapy and for cognitive-behavioral therapy (CBT). This study examined whether joint treatment offers additional benefit.

METHOD

Patients with DSM-IV hypochondriasis (N=195) were randomly assigned to one of four treatments-placebo, CBT, fluoxetine, or joint treatment with both fluoxetine and CBT. Evaluations assessed hypochondriasis, other psychopathology, adverse events, functional status, and quality of life. The primary analysis assessed outcome at week 24 among the intent-to-treat sample, with responders defined as having a 25% or greater improvement over baseline on both the Whiteley Index and a modified version of the Yale-Brown Obsessive Compulsive Scale for hypochondriasis (H-YBOCS-M). The Cochran-Armitage trend test assessed the hypothesized pattern of response: joint treatment > CBT or fluoxetine treatment > placebo treatment.

RESULTS

The predicted pattern of response was statistically significant, as shown by the following responder rates: joint treatment group, 47.2%; single active treatment group, 41.8%; and placebo group, 29.6%. Responder rates for each active treatment were not significantly different from the rate for placebo. Secondary analyses of the Whiteley Index as a continuous measure revealed that, compared with placebo, fluoxetine (but not CBT) was significantly more effective at week 24 in reducing hypochondriasis and had a significantly faster rate of improvement over 24 weeks. Fluoxetine also resulted in significantly less anxiety and better quality of life than placebo. Dropout rates did not differ between groups, and treatment-emergent adverse events were evenly distributed.

CONCLUSIONS

This study supports the safety, tolerance, and efficacy of fluoxetine for hypochondriasis. Joint treatment provided a small incremental benefit. Because approximately 50% of patients did not respond to the study treatments, new or more intensive approaches are needed.

Response of Htr3a knockout mice to antidepressant treatment and chronic stress

BACKGROUND AND PURPOSE

It has recently been suggested that 5-HT₃ receptor blockade enhances the efficacy of selective 5-HT (serotonin) reuptake inhibitor (SSRI) antidepressants and may reverse stress-induced deficits in rodents.

EXPERIMENTAL APPROACH

To further explore this hypothesis, we used mice lacking the 5-HT₃ receptor (Htr3a KO) and their wild-type (WT) controls to assess their response in behavioural paradigms relevant to anxiety and depression. Mice were studied under basal, antidepressant treatments and chronic social defeat stress (CSDS) conditions.

KEY RESULTS

In basal conditions, Htr3a KO mice displayed anxiolytic- and antidepressant-like behaviours in the elevated plus maze, the social interaction and the forced swim tests (FST), but behaved as WT mice in response to acute citalopram in the FST. However, the effects of fluoxetine were blunted in Htr3a KO mice in these same tests. In an in vitro electrophysiological paradigm, a low-dose citalopram treatment triggered 5-HT_1A receptor desensitization only in the dorsal raphe nucleus of Htr3a KO, although a high dose desensitized 5-HT_1A autoreceptor function equally in Htr3a KO and WT mice, suggesting that citalopram may become effective at lower doses when 5-HT₃ receptors are inactivated. In addition, Htr3a deletion blocked CSDS-induced modification in the cortical expression of two genes involved in oxidative stress, CaMKIIa and SOD1.

CONCLUSIONS AND IMPLICATIONS

Taken together, these data show that Htr3a deletion promotes SSRI efficacy and prevents the occurrence of stress-induced deleterious effects, suggesting that the 5-HT₃ receptor may represent an interesting target for the treatment of stress-related disorders.

Looking into the brain through the retinal ganglion cells in psychiatric disorders: A review of evidences

Psychiatry and neuroscience research need novel approaches to indirectly investigate brain function. As the retina is an anatomical and developmental extension of the central nervous system (CNS), changes in retinal function may reflect neurological dysfunctions in psychiatric disorders. The last and most integrated retinal relay before visual information transfer to the brain is the ganglion cell layer. Here, based on collected arguments, we argue that these cells offer a crucial site for indirectly investigating brain function. We describe the anatomical and physiological properties of these cells together with measurements of their functional properties named pattern electroretinogram (PERG). Based on ganglion cell dysfunctions measured with PERG in neurological disorders, we argue for the relevance of studying ganglion cell function in psychiatric research. We review studies that have evaluated ganglion cell function in psychiatric and addictive disorders and discuss how changes in PERG measurements could be functional markers of pathophysiological mechanisms of psychiatric disorders.

A Pilot Study: Cardiac Parameters in Children Receiving New-Generation Antidepressants

OBJECTIVE

Because of concerns about potential associations between high doses of citalopram and QTc prolongation in adults, this study examined whether such associations are operant in children. We hypothesized that therapeutic doses of nontricyclic antidepressant medications (non-TCAs) prescribed to children would be cardiovascularly safe.

STUDY DESIGN

The sample consisted of 49 psychiatrically referred children and adolescents 6 to 17 years old of both sexes treated with a non-TCA (citalopram, escitalopram, fluoxetine, paroxetine, sertraline, bupropion, duloxetine, venlafaxine, mirtazapine). To standardize the doses of different antidepressants, we converted doses of individual medicines into "citalopram equivalent doses" (CEDs) based on dosing recommendation for individual antidepressants. Correlation analysis was carried out to compare the continuous and weight-based CED to variables of interest. A QTc grouping was defined as normal, borderline, or abnormal, and CED was compared across QTc groupings using linear regression. An antidepressant dosage group was defined as low or high dose, and a t test compared variables of interest across dosage groups.

RESULTS

No significant associations were found between total or weight-corrected CEDs of any antidepressant examined and QTc or any other electrocardiogram or blood pressure parameters. In patients taking citalopram or escitalopram, a significant correlation was found between PR interval and total daily dose, which disappeared when weight-based doses were used or when corrected by age.

CONCLUSIONS

Although limited by a relatively small sample size, these results suggest that therapeutic doses of non-TCA antidepressants when used in children do not seem to be associated with prolonged QTc interval or other adverse cardiovascular effects.

Attenuation of postprandial blood glucose in humans consuming isomaltodextrin: carbohydrate loading studies

Background: Isomaltodextrin (IMD) is a novel highly branched α-glucan and its function as a soluble dietary fiber is expected. Objective: The goal of this study was to evaluate the effects of IMD on postprandial glucose excursions in healthy people and to make the mechanism clear. Design: Twenty-nine subjects ingested a solution containing maltodextrin (MD) or sucrose with or without IMD. Fourteen subjects ingested a solution containing glucose with or without IMD. Blood glucose concentrations were then compared between the groups. Furthermore, in vitro digestion, inhibition of digestive enzymes, and glucose absorption tests were conducted. Results: IMD attenuated blood glucose elevation in the subjects with blood glucose excursions at the high end of normal following the ingestion of MD or sucrose or glucose alone. This effect of 5 g IMD was most clear. IMD was digested partially only by small intestinal mucosal enzymes, and maltase and isomaltase activities were weakly inhibited. Furthermore, IMD inhibited the transport of glucose from mucosal side to serosal side. Conclusions: IMD attenuated postprandial blood glucose, after the ingestion of MD or sucrose or glucose. As one of the mechanism, it was suggested that IMD inhibited the absorption of glucose on small intestinal mucosal membrane.

Desipramine decreases expression of human and murine indoleamine-2,3-dioxygenases

Abundant evidence connects depression symptomology with immune system activation, stress and subsequently elevated levels of kynurenine. Anti-depressants, such as the tricyclic norepinephrine/serotonin reuptake inhibitor desipramine (Desip), were developed under the premise that increasing extracellular neurotransmitter level was the sole mechanism by which they alleviate depressive symptomologies. However, evidence suggests that anti-depressants have additional actions that contribute to their therapeutic potential. The Kynurenine Pathway produces tryptophan metabolites that modulate neurotransmitter activity. This recognition identified another putative pathway for anti-depressant targeting. Considering a recognized role of the Kynurenine Pathway in depression, we investigated the potential for Desip to alter expression of rate-limiting enzymes of this pathway: indoleamine-2,3-dioxygenases (Ido1 and Ido2). Mice were administered lipopolysaccharide (LPS) or synthetic glucocorticoid dexamethasone (Dex) with Desip to determine if Desip alters indoleamine-dioxygenase (DO) expression in vivo following a modeled immune and stress response. This work was followed by treating murine and human peripheral blood mononuclear cells (PBMCs) with interferon-gamma (IFNγ) and Desip. In vivo: Desip blocked LPS-induced Ido1 expression in hippocampi, astrocytes, microglia and PBMCs and Ido2 expression by PBMCs. Ex vivo: Desip decreased IFNγ-induced Ido1 and Ido2 expression in murine PBMCs. This effect was directly translatable to the human system as Desip decreased IDO1 and IDO2 expression by human PBMCs. These data demonstrate for the first time that an anti-depressant alters expression of Ido1 and Ido2, identifying a possible new mechanism behind anti-depressant activity. Furthermore, we propose the assessment of PBMCs for anti-depressant responsiveness using IDO expression as a biomarker.

A Review of Psychopharmacological Interventions Post-Disaster to Prevent Psychiatric Sequelae

BACKGROUND

Disasters are mega-scale catastrophic events which cause trauma and mental health sequelae. A review of early pharmacological interventions for the prevention of psychiatric disorders following disasters is sorely needed.

METHODS

A literature search of "Psychiatric Sequelae AND Disasters", "Disaster mental health/Disaster psychiatry", "Psychotropics AND Disasters", and "Drug therapy AND Disasters" yielded 213 articles, 38 of which were included in the review.

RESULTS

Common post-disaster psychiatric conditions are: posttraumatic stress disorder (PTSD), depressive and anxiety disorders, substance use disorders and medically-unexplained psychological symptoms. Early psychopharmacological interventions to prevent PTSD provide promising evidence for hydrocortisone in medically ill trauma populations. Less robust benefits were noted for other pharmacological interventions. No reported trials have explored prevention of depression or other common post-disaster psychiatric conditions.

CONCLUSION

Hydrocortisone shows promise in preventing and reducing the psychiatric sequelae of PTSD following disasters. Further evaluation of hydrocortisone and other potentially beneficial psychopharmacological interventions are needed.

Autoimmune Aspects of Neurodegenerative and Psychiatric Diseases: A Template for Innovative Therapy

Neurodegenerative and psychiatric diseases (NPDs) are today's most important group of diseases, surpassing both atherosclerotic cardiovascular disease and cancer in morbidity incidence. Although NPDs have a dramatic impact on our society because of their high incidence, mortality, and severe debilitating character, remarkably few effective interventions have become available. The current treatments, if available, comprise the lifelong intake of general immunosuppressants to delay disease progression or neurotransmitter antagonists/agonists to dampen undesired behaviors. The long-term usage of such medication, however, coincides with often severe adverse side effects. There is, therefore, an urgent need for safe and effective treatments for these diseases. Here, we discuss that many NPDs coincide with subtle chronic or flaring brain inflammation sometimes escalating with infiltrations of lymphocytes in the inflamed brain parts causing mild to severe or even lethal brain damage. Thus, NPDs show all features of autoimmune diseases. In this review, we postulate that NPDs resemble autoimmune-driven inflammatory diseases in many aspects and may belong to the same disease spectrum. Just like in autoimmune diseases, NPD symptoms basically are manifestations of a chronic self-sustaining inflammatory process with detrimental consequences for the patient. Specific inhibition of the destructive immune responses in the brain, leaving the patient's immune system intact, would be the ultimate solution to cure patients from the disease. To reach this goal, the primary targets, e.g., the primary self-antigens (pSAgs) of the patient's chronic (auto)immune response, need to be identified. For a few major NPDs, immunological studies led to the identification of the pSAgs involved in the autoimmune damage of specific brain parts. However, further research is needed to complete the list of pSAgs for all NPDs. Such immunological studies will not only provide crucial insights into NPD pathogenesis but also ultimately enable the development of a new generation of safe and effective immunotherapies for NPDs. Interventions that will dramatically improve the life expectancy and quality of life of individual patients and, moreover, will significantly reduce the health-care costs of the society in general.

Influence of fluvoxamine on plasma interleukin-6 or clinical improvement in patients with major depressive disorder

OBJECTIVES

The etiology of depression remains unknown. There is, however, a growing body of evidence that cytokines are involved in the pathophysiology of depression. The aim of this study is to investigate the effects of fluvoxamine on plasma interleukin-6 (IL-6) levels and on clinical improvement of the depressive state.

SUBJECTS AND METHODS

Thirty patients who met the DSM-IV criteria for major depressive disorder (MDD) were enrolled in the study. Thirteen were male and 17 were female, and their ages ranged from 26 to 70 years (mean ± standard deviation 45.0±14.2). The patients were treated with fluvoxamine for 8 weeks. The dosages of fluvoxamine varied among the patients and, based on ethical considerations, were not fixed.

RESULTS

The fluvoxamine doses were positively related to plasma fluvoxamine levels (r =0.8798, P<0.001). A significant correlation was observed between the patients' plasma IL-6 levels and their 17-item Hamilton Rating Scale for Depression (HAMD17) scores (r =0.4555, P=0.0010). A positive correlation was found between the delta plasma IL-6 (week 0-week 8) and the delta HAMD17 (week 0-week 8) (r =0.5226, P=0.002).

CONCLUSION

Effect of fluvoxamine on IL-6 is partially associated with its clinical efficacy for MDD.

Systems genetics analysis of pharmacogenomics variation during antidepressant treatment

Selective serotonin reuptake inhibitors (SSRIs) are the most widely used antidepressants, but the efficacy of the treatment varies significantly among individuals. It is believed that complex genetic mechanisms play a part in this variation. We have used a network based approach to unravel the involved genetic components. Moreover, we investigated the potential difference in the genetic interaction networks underlying SSRI treatment response over time. We found four hub genes (ASCC3, PPARGC1B, SCHIP1 and TMTC2) with different connectivity in the initial SSRI treatment period (baseline to week 4) compared with the subsequent period (4-8 weeks after initiation), suggesting that different genetic networks are important at different times during SSRI treatment. The strongest interactions in the initial SSRI treatment period involved genes encoding transcriptional factors, and in the subsequent period genes involved in calcium homeostasis. In conclusion, we suggest a difference in genetic interaction networks between initial and subsequent SSRI response.

Raising the Minimum Effective Dose of Serotonin Reuptake Inhibitor Antidepressants: Adverse Drug Events

This review focuses on the dose-response of serotonin reuptake inhibitor (SRI) antidepressants for efficacy and for adverse drug events (ADEs). Dose-response is identified by placebo-controlled, double-blind, fixed-dose clinical trials comparing various doses for efficacy and for ADEs. Reports from the great majority of clinical trials have consistently found that the minimum SRI effective dose is usually optimal for efficacy in the treatment of depression disorders, even though most American medical practitioners raise the dose when early antidepressant treatment results are negative or partial. To better understand this issue, the medical literature was comprehensively reviewed to ascertain the degree to which SRI medications resulted in a flat dose response for efficacy and then to identify specific ADEs that are dose-dependent. Strong evidence from fixed-dose trial data for the efficacy of nonascendant, minimum effective doses of SRIs was found for the treatment of both major depression and anxiety disorders. Particularly important was the finding that most SRI ADEs have an ascending dose-response curve. These ADEs include sexual dysfunction, hypertension, cardiac conduction risks, hyperglycemia, decreased bone density, sweating, withdrawal symptoms, and agitation. Thus, routinely raising the SRI dose above the minimum effective dose for efficacy can be counter-productive.

Major depressive disorder

Major depressive disorder (MDD) is a debilitating disease that is characterized by depressed mood, diminished interests, impaired cognitive function and vegetative symptoms, such as disturbed sleep or appetite. MDD occurs about twice as often in women than it does in men and affects one in six adults in their lifetime. The aetiology of MDD is multifactorial and its heritability is estimated to be approximately 35%. In addition, environmental factors, such as sexual, physical or emotional abuse during childhood, are strongly associated with the risk of developing MDD. No established mechanism can explain all aspects of the disease. However, MDD is associated with alterations in regional brain volumes, particularly the hippocampus, and with functional changes in brain circuits, such as the cognitive control network and the affective-salience network. Furthermore, disturbances in the main neurobiological stress-responsive systems, including the hypothalamic-pituitary-adrenal axis and the immune system, occur in MDD. Management primarily comprises psychotherapy and pharmacological treatment. For treatment-resistant patients who have not responded to several augmentation or combination treatment attempts, electroconvulsive therapy is the treatment with the best empirical evidence. In this Primer, we provide an overview of the current evidence of MDD, including its epidemiology, aetiology, pathophysiology, diagnosis and treatment.

Core Concepts Involving Adverse Psychotropic Drug Effects: Assessment, Implications, and Management

Adverse effects from psychiatric drugs can profoundly influence treatment adherence and outcomes. Good care involves addressing adverse effects no differently than any other component of treatment. Knowledge about adverse effect assessment and management fosters a proper context that helps clinicians not sacrifice a drug's potential therapeutic benefits because of greater concerns about its tolerability. This article provides an overview of basic concepts related to the assessment and management of suspected adverse effects from psychotropic drugs. Key points are discussed regarding clinical, pharmacogenetic, pharmacokinetic, and pharmacodynamic risk factors for treatment-emergent adverse effects, alongside recommendations for their systematic assessment.

Early life stress predicts thalamic hyperconnectivity: A transdiagnostic study of global connectivity

Early life stress (ELS) is an established risk factor for psychiatric illness and is associated with altered functional connectivity within- and between intrinsic neural networks. The widespread nature of these disruptions suggests that broad imaging measures of neural connectivity, such as global based connectivity (GBC), may be particularly appropriate for studies of this population. GBC is designed to identify brain regions having maximal functional connectedness with the rest of the brain, and alterations in GBC may reflect a restriction or broadening of network synchronization. We evaluated whether ELS severity predicted GBC in a sample (N = 46) with a spectrum of ELS exposure. Participants included healthy controls without ELS, those with at least moderate ELS but without psychiatric disorders, and a group of patients with ELS- related psychiatric disorders. The spatial distribution of GBC peaked in regions of the salience and default mode networks, and ELS severity predicted increased GBC of the left thalamus (corrected p < 0.005, r = 0.498). Thalamic connectivity was subsequently evaluated and revealed reduced connectivity with the salience network, particularly the dorsal anterior cingulate cortex (corrected p < 0.005), only in the patient group. These findings support a model of disrupted thalamic connectivity in ELS and trauma-related negative affect states, and underscore the importance of a transdiagnostic, dimensional neuroimaging approach to understanding the sequelae of trauma exposure.

Pharmacokinetic Pharmacogenetic Prescribing Guidelines for Antidepressants: A Template for Psychiatric Precision Medicine

Antidepressants are commonly prescribed medications in the United States, and there is increasing interest in individualizing treatment selection for more than 20 US Food and Drug Administration-approved treatments for major depressive disorder. Providing greater precision to pharmacotherapeutic recommendations for individual patients beyond the large-scale clinical trials evidence base can potentially reduce adverse effect toxicity profiles and increase response rates and overall effectiveness. It is increasingly recognized that genetic variation may contribute to this differential risk to benefit ratio and thus provides a unique opportunity to develop pharmacogenetic guidelines for psychiatry. Key studies and concepts that review the rationale for cytochrome P450 2D6 (CYP2D6) and cytochrome P450 2C19 (CYP2C19) genetic testing can be delineated by serum levels, adverse events, and clinical outcome measures (eg, antidepressant response). In this article, we report the evidence that contributed to the implementation of pharmacokinetic pharmacogenetic guidelines for antidepressants primarily metabolized by CYP2D6 and CYP2C19.

Comparative efficacy of selective serotonin reuptake inhibitors (SSRI) in treating major depressive disorder: a protocol for network meta-analysis of randomised controlled trials

INTRODUCTION

There have been inconsistent findings from randomised controlled trials (RCTs) and systematic reviews on the efficacies of selective serotonin reuptake inhibitors (SSRIs) as the first-line treatment of major depressive disorder (MDD). Besides inconsistencies among randomised controlled trials (RCTs), their risks of bias and evidence grading have seldom been evaluated in meta-analysis. This study aims to compare the efficacy of SSRIs by conducting a Bayesian network meta-analysis, which will be the most comprehensive evaluation of evidence to resolve the inconsistency among previous studies.

METHODS AND ANALYSES

SSRIs including citalopram, escitalopram, fluoxetine, fluvoxamine, paroxetine, sertraline and vilazodone have been selected. Systematic database searching and screening will be conducted for the RCTs on drug treatment of patients with MDD according to pre-specified search strategies and selection criteria. PubMed, the Cochrane Library, EMBASE, ScienceDirect, the US Food and Drug Administration Website, ClinicalTrial.gov and WHO Clinical Trials will be searched. Outcome data including Hamilton Depression Rating Scale (HDRS), Montgomery-Åsberg Depression Rating Scale (MADRS) and Clinical Global Impression (CGI) from eligible RCTs will be extracted. The outcomes will be analysed as ORs and mean differences under a random-effects model. A Bayesian network meta-analysis will be conducted with WinBUGS software, to compare the efficacies of SSRIs. Subgroup and sensitivity analysis will be performed to explain the study heterogeneity and evaluate the robustness of the results. Meta-regression analysis will be conducted to determine the possible factors affecting the efficacy outcomes. The Cochrane risk of bias assessment tool will be used to assess the RCT quality, and the Grading of Recommendation, Assessment, Development and Evaluation will be used to assess the strength of evidence from the meta-analysis.

ETHICS AND DISSEMINATION

No ethical approval is required because this study includes neither confidential personal patient data nor interventions with patients.

PROTOCOL REGISTRATION NUMBER

CRD42015024879.

A mega-analysis of fixed-dose trials reveals dose-dependency and a rapid onset of action for the antidepressant effect of three selective serotonin reuptake inhibitors

The possible dose-dependency for the antidepressant effect of selective serotonin reuptake inhibitors (SSRIs) remains controversial. We believe we have conducted the first comprehensive patient-level mega-analysis exploring this issue, one incentive being to address the possibility that inclusion of low-dose arms in previous meta-analyses may have caused an underestimation of the efficacy of these drugs. All company-sponsored, acute-phase, placebo-controlled, fixed-dose trials using the Hamilton Depression Rating Scale (HDRS) and conducted to evaluate the effect of citalopram, paroxetine or sertraline in adult major depression were included (11 trials, n=2859 patients). The single-item depressed mood, which has proven a more sensitive measure to detect an antidepressant signal than the sum score of all HDRS items, was designated the primary effect parameter. Doses below or at the lower end of the usually recommended dose range (citalopram: 10-20 mg, paroxetine: 10 mg; sertraline: 50 mg) were superior to placebo but inferior to higher doses, hence confirming a dose-dependency to be at hand. In contrast, among doses above these, there was no indication of a dose-response relationship. The effect size (ES) after exclusion of suboptimal doses was of a more respectable magnitude (0.5) than that usually attributed to the antidepressant effect of the SSRIs. In conclusion, the observation that low doses are less effective than higher ones challenges the oft-cited view that the effect of the SSRIs is not dose-dependent and hence not caused by a specific, pharmacological antidepressant action. Moreover, we suggest that inclusion of suboptimal doses in previous meta-analyses has led to an underestimation of the efficacy of these drugs.

[How to define treatment-resistant depression?]

The most largely used definition of the treatment-resistant depression relies on the failure of two successive trials of antidepressant treatment at an adequate dose and duration. The absence of response to previous antidepressant treatments should be assessed using specific and appropriate clinical instruments enabling a correct staging of the therapeutic resistance. A wide range of socio-demographic and clinical factors (i.e. psychiatric/somatic comorbidities) are classically associated with the therapeutic resistance. The aim of the treatment of major depression is to achieve a complete clinical remission. The presence of residual symptoms increases the risk for the subsequent occurrence of relapses and recurrences, hence facilitating the development of therapeutic resistance. The treatment-resistant depression has a deleterious impact on the social, familial or professional functioning, thereby leading to an impaired quality of life with serious socioeconomic consequences and costs.

Major Depressive Disorder and Kappa Opioid Receptor Antagonists

Major depressive disorder (MDD) is a common psychiatric disease worldwide. The clinical use of tricyclic antidepressants (TCAs), monoamine oxidase inhibitors (MAOIs) and selective serotonin reuptake inhibitors (SSRIs)/serotonin-norepinephrine reuptake inhibitor (SNRIs) for this condition have been widely accepted, but they were challenged by unacceptable side-effects, potential drug-drug interactions (DDIs) or slow onset/lack of efficacy. The endogenous opioid system is involved in stress and emotion regulatory processes and its role in MDD has been implicated. Although several KOR antagonists including JDTic and PF-04455242 were discontinued in early clinical trials, ALKS 5461 and CERC-501(LY-2456302) survived and entered into Phase-III and Phase-II trials, respectively. Considering the efficacy and safety of early off-label use of buprenorphine in the management of the treatment-resistant depression (TRD), it will be not surprising to predict the potential success of ALKS 5461 (a combination of buprenorphine and ALKS-33) in the near future. Moreover, CERC-501 will be expected to be available as monotherapy or adjuvant therapy with other first-line antidepressants in the treatment of TRD, if ongoing clinical trials continue to provide positive benefit-risk profiles. Emerging new researches might bring more drug candidates targeting the endogenous opioid system to clinical trials to address current challenges in MDD treatment in clinical practice.