Intranasal Ketamine for Depression in Adults: A Systematic Review and Meta-Analysis of Randomized, Double-Blind, Placebo-Controlled Trials

Efficacy and safety of peri-partum Esketamine for prevention of post-partum depression in women undergoing caesarian section: A meta-analysis and systematic review of randomized controlled trials

Postpartum depression (PPD) is a psychiatric condition affecting women post-childbirth. Medication combined with psychotherapy, is the current protocol for its treatment. A meta-analysis was conducted using RevMan 5.4 to explore the efficacy and safety of peri-partum administration of esketamine for preventing PPD. After searching several databases to retrieve the relevant RCTs, seven were included in this analysis, with dichotomous data presented as risk ratio and continuous data as mean difference. The study found a lower incidence of PPD in the esketamine group compared to the control group (RR= 0.37), with significant difference in EPDS scores between the two groups (MD= -1.23) in the first week postpartum. The esketamine group reported a lower prevalence of PPD 4-6 weeks postpartum (RR= 0.48), and no significant difference in EPDS scores after 4 weeks postpartum (MD = -0.10). The esketamine group had a significantly higher incidence of hallucination (RR= 13.85). Other adverse effects, such as dizziness (RR= 4.09), nausea (RR= 0.88), vomiting (RR=0.74), headache (RR=1.52), nightmares (RR=1.22), pruritus (RR=0.29), and drowsiness (RR=1.57) did not show significant differences between the two groups. The study found that esketamine, with manageable side effects, reduces the prevalence of post-partum depression (PPD) after one week as well as after four to six weeks. However, the findings are limited by the limited number of available RCTs, and future research should determine the ideal dosage, the most effective method of administration and the long-term safety profile of esketamine so that it may be considered as an adjunct therapy or a potential sole treatment option.

Ketamine for mood disorders, anxiety, and suicidality in children and adolescents: a systematic review

Mood disorders, anxiety, and suicidality in youth are increasing and rapid-acting treatments are urgently needed. One potential is ketamine or its enantiomer esketamine, which was FDA approved in 2019 to treat major depressive disorder with suicidality in adults. This systematic review evaluated the evidence for the clinical use of ketamine to treat mood disorders, anxiety, and suicidality in youth. The PRISMA guidelines were used, and a protocol registered prospectively ( https://osf.io/9ucsg/ ). The literature search included Pubmed/MEDLINE, Ovid/MEDLINE, Scopus, CINAHL, PsychInfo, and Google Scholar. Trial registries and preprint servers were searched, and authors contacted for clarification. Studies reported on the clinical use of ketamine to treat anxiety, depression, bipolar disorder, or suicidality in youth ≤19 years old and assessed symptoms before and after ketamine use. Study screening and data extraction were conducted independently by 2-4 authors. Safety, tolerability, and efficacy data were collected. The Cochrane Risk of Bias guidelines assessed the quality of the evidence. Twenty-two published reports based on 16 studies were identified: 7 case studies, 6 observational studies, 3 randomized trials, and 6 secondary data analyses. Studies reported immediate improvements in depression, anxiety, and suicidality. Improvements were maintained for weeks-months following treatment. Ketamine was well-tolerated with the most common side effects being dizziness, nausea, and mild dissociation. Transient hemodynamic changes were reported, all of which resolved quickly and did not require medical intervention. Initial evidence suggests ketamine is safe and may be effective for mood disorders, anxiety, and suicidality in youth. Further randomized trials are warranted.

Efficacy and safety of ketamine and esketamine for unipolar and bipolar depression: an overview of systematic reviews with meta-analysis

Background

Unipolar and bipolar depression present treatment challenges, with patients sometimes showing limited or no response to standard medications. Ketamine and its enantiomer, esketamine, offer promising alternative treatments that can quickly relieve suicidal thoughts. This Overview of Reviews (OoR) analyzed and synthesized systematic reviews (SRs) with meta-analysis on randomized clinical trials (RCTs) involving ketamine in various formulations (intravenous, intramuscular, intranasal, subcutaneous) for patients with unipolar or bipolar depression. We evaluated the efficacy and safety of ketamine and esketamine in treating major depressive episodes across various forms, including unipolar, bipolar, treatment-resistant, and non-resistant depression, in patient populations with and without suicidal ideation, aiming to comprehensively assess their therapeutic potential and safety profile.

Methods

Following PRIOR guidelines, this OoR's protocol was registered on Implasy (ID:202150049). Searches in PubMed, Scopus, Cochrane Library, and Epistemonikos focused on English-language meta-analyses of RCTs of ketamine or esketamine, as monotherapy or add-on, evaluating outcomes like suicide risk, depressive symptoms, relapse, response rates, and side effects. We included studies involving both suicidal and non-suicidal patients; all routes and formulations of administration (intravenous, intramuscular, intranasal) were considered, as well as all available comparisons with control interventions. We excluded meta-analysis in which the intervention was used as anesthesia for electroconvulsive therapy or with a randomized ascending dose design. The selection, data extraction, and quality assessment of studies were carried out by pairs of reviewers in a blinded manner. Data on efficacy, acceptability, and tolerability were extracted.

Results

Our analysis included 26 SRs and 44 RCTs, with 3,316 subjects. The intervention is effective and well-tolerated, although the quality of the included SRs and original studies is poor, resulting in low certainty of evidence.

Limitations

This study is limited by poor-quality SRs and original studies, resulting in low certainty of the evidence. Additionally, insufficient available data prevents differentiation between the effects of ketamine and esketamine in unipolar and bipolar depression.

Conclusion

While ketamine and esketamine show promising therapeutic potential, the current evidence suffers from low study quality. Enhanced methodological rigor in future research will allow for a more informed application of these interventions within the treatment guidelines for unipolar and bipolar depression.

Systematic review registration

[https://inplasy.com/inplasy-2021-5-0049/], identifier (INPLASY202150049).

Neuroplasticity: Pathophysiology and Role in Major Depressive Disorder

Neuroplasticity is characterized by the brain's ability to change its activity in response to extrinsic and intrinsic factors and is thought to be the mechanism behind all brain functions. Neuroplasticity causes structural and functional changes on a molecular level, specifically the growth of different regions in the brain and changes in synaptic and post-synaptic activities. The four types of neuroplasticity are homologous area adaption, compensatory masquerade, cross-modal reassignment, and map expansion. All of these help the brain work around injuries or new information inputs. In addition to baseline physical functions, neuroplasticity is thought to be the basis of emotional and mental regulations and the impairment of it can cause various mental illnesses. Concurrently, these mental illnesses further the damage of synaptic plasticity in the brain. Major depressive disorder (MDD) is one of the most common mental illnesses. It is affected by and accelerates the impairment of neuroplasticity. It is characterized by a chronically depressed state of mind that can impact the patient's daily life, including work life and interests. This review will focus on highlighting the physiological aspects of the disease and the role of neuroplasticity in the pathogenesis and pathology of the disorder. Moreover, the role of monoamine regulation and ketamine uptake will be discussed in terms of their antidepressant effects on the outcomes of MDD.

Intramuscular ketamine vs. midazolam for rapid risk-reduction in suicidal, depressed emergency patients: Clinical trial design and rationale

Emergency department (ED) visits for suicidal ideation or behavior have been increasing in all age groups, particularly younger adults. A rapid-acting treatment to reduce suicidal thinking, adapted for ED use, is needed. Previous studies have shown a single dose of ketamine can improve depression and suicidal ideation within hours. However, most studies used 40 min intravenous infusions which can be impractical in a psychiatric ED. The ER-Ketamine study we describe here is a randomized midazolam-controlled clinical trial (RCT; NCT04640636) testing intramuscular (IM) ketamine's feasibility, safety, and effectiveness to rapidly reduce suicidal ideation and depression in a psychiatric ED. A pre-injection phase involves screening, informed consent, eligibility confirmation, and baseline assessment of suicidal ideation, depression, and comorbidities. The randomized double-blind IM injection is administered in the ED under research staff supervision, vital sign monitoring, pharmacokinetic blood sampling, and clinical assessments. The post-injection phase occurs on a psychiatric inpatient unit with follow-up research assessments through four weeks post-discharge. Outcome measures are feasibility, safety, and effects on suicidal ideation and depression at 24 h post-injection, and through follow-up. The target sample is N = 90 adults in a major depressive episode, assessed by ED clinicians as warranting hospitalization for suicide risk. Here we report design, rationale, and preliminary feasibility and safety for this ongoing study. Demographics of the 53 participants (ages 18 to 65 years) randomized to date suggest a diverse sample tending towards younger adults.

Insights into the neurobiology of suicidality: explicating the role of glutamatergic systems through the lens of ketamine

Suicidality is a prevalent mental health condition, and managing suicidal patients is one of the most challenging tasks for health care professionals due to the lack of rapid-acting, effective psychopharmacological treatment options. According to the literature, suicide has neurobiological underpinnings that are not fully understood, and current treatments for suicidal tendencies have considerable limitations. To treat suicidality and prevent suicide, new treatments are required; to achieve this, the neurobiological processes underlying suicidal behavior must be thoroughly investigated. Although multiple neurotransmitter systems, particularly serotonergic systems, have been studied in the past, less has been reported in relation to disruptions in glutamatergic neurotransmission, neuronal plasticity, and neurogenesis that result from stress-related abnormalities of the hypothalamic-pituitary-adrenal system. Informed by the literature, which reports robust antisuicidal and antidepressive properties of subanaesthetic doses of ketamine, this review aims to provide an examination of the neurobiology of suicidality (and relevant mood disorders) with implications of pertinent animal, clinical, and postmortem studies. We discuss dysfunctions in the glutamatergic system, which may play a role in the neuropathology of suicidality and the role of ketamine in restoring synaptic connectivity at the molecular levels.

History repeating: guidelines to address common problems in psychedelic science

Research in the last decade has expressed considerable optimism about the clinical potential of psychedelics for the treatment of mental disorders. This optimism is reflected in an increase in research papers, investments by pharmaceutical companies, patents, media coverage, as well as political and legislative changes. However, psychedelic science is facing serious challenges that threaten the validity of core findings and raise doubt regarding clinical efficacy and safety. In this paper, we introduce the 10 most pressing challenges, grouped into easy, moderate, and hard problems. We show how these problems threaten internal validity (treatment effects are due to factors unrelated to the treatment), external validity (lack of generalizability), construct validity (unclear working mechanism), or statistical conclusion validity (conclusions do not follow from the data and methods). These problems tend to co-occur in psychedelic studies, limiting conclusions that can be drawn about the safety and efficacy of psychedelic therapy. We provide a roadmap for tackling these challenges and share a checklist that researchers, journalists, funders, policymakers, and other stakeholders can use to assess the quality of psychedelic science. Addressing today's problems is necessary to find out whether the optimism regarding the therapeutic potential of psychedelics has been warranted and to avoid history repeating itself.

Safety and tolerability of intramuscular and sublingual ketamine for psychiatric treatment in the Roots To Thrive ketamine-assisted therapy program: a retrospective chart review

Background

In the last few years, ketamine is becoming increasingly common in the treatment of mental health conditions, but there is a lack of safety data informing intramuscular and sublingual dosing in a community-focused group psychotherapy setting. The Roots To Thrive ketamine-assisted therapy (RTT-KaT) program is a unique 12-week RTT-KaT program with 12 community of practice (a form of group therapy) sessions and three ketamine medicine sessions.

Objectives

This study reports on adverse effects of intramuscular and sublingual ketamine dosing in a community group psychotherapy setting among 128 participants across four cohorts.

Design

Retrospective chart review.

Methods

A chart review of the RTT-KaT Program was performed retrospectively on four cohorts (n = 128) that participated in 448 sessions running between September 2020 and December 2021. Baseline characteristics and adverse events were captured including medication administration before, during, and after RTT-KaT sessions. Analyses by session and by individual were conducted. Chi-square test with Yates' continuity correction was used to assess side effects in subgroups from ketamine administration.

Results

RTT-KaT was well tolerated with none of the 128 participants dropping out of the program. Primarily, of the 448 sessions, 49.16% had elevated blood pressures post-KaT session by session. In terms of other adverse effects, 12.05% of participant-sessions experienced nausea, 2.52% had an episode of vomiting, 3.35% had a headache, and seven participant-sessions experienced dizziness. Analysis by individual revealed congruent findings.

Conclusion

These findings suggest good safety and tolerability for RTT-KaT among individuals seeking treatment for mental health issues. The majority of participants did not experience adverse reactions and the adverse events that were recorded involved transient symptoms that were resolved with rest and/or medications. The group therapy model described provides a comprehensive approach and presents a promising model for operating a KaT program in a community setting.

Treating bipolar depression with esketamine: Safety and effectiveness data from a naturalistic multicentric study on esketamine in bipolar versus unipolar treatment-resistant depression

BACKGROUND

Bipolar depression accounts for most of the disease duration in type I and type II bipolar disorder (BD), with few treatment options, often poorly tolerated. Many individuals do not respond to first-line therapeutic options, resulting in treatment-resistant bipolar depression (B-TRD). Esketamine, the S-enantiomer of ketamine, has recently been approved for treatment-resistant depression (TRD), but no data are available on its use in B-TRD.

OBJECTIVES

To compare the efficacy of esketamine in two samples of unipolar and bipolar TRD, providing preliminary indications of its effectiveness in B-TRD. Secondary outcomes included the evaluation of the safety and tolerability of esketamine in B-TRD, focusing on the average risk of an affective switch.

METHODS

Thirty-five B-TRD subjects treated with esketamine nasal spray were enrolled and compared with 35 TRD patients. Anamnestic data and psychometric assessments (Montgomery-Asberg Depression Rating Scale/MADRS, Hamilton-depression scale/HAM-D, Hamilton-anxiety scale/HAM-A) were collected at baseline (T0), at one month (T1), and three months (T2) follow up.

RESULTS

A significant reduction in depressive symptoms was found at T1 and T2 compared to T0, with no significant differences in response or remission rates between subjects with B-TRD and TRD. Esketamine showed a greater anxiolytic action in subjects with B-TRD than in those with TRD. Improvement in depressive symptoms was not associated with treatment-emergent affective switch.

CONCLUSIONS

Our results supported the effectiveness and tolerability of esketamine in a real-world population of subjects with B-TRD. The low risk of manic switch in B-TRD patients confirmed the safety of this treatment.

Pharmacologic Approaches to Suicide Prevention

Suicide is a leading cause of death that is often preventable. This article reviews the role of medications in treating suicidal behavior and in preventing suicide. For an acute suicidal crisis, ketamine, and perhaps esketamine, are emerging as important tools. For patients with chronic suicidality, clozapine remains the only U.S. Food and Drug Administration (FDA) approved antisuicidal medication, and its use is predominantly for patients with schizophrenia and schizoaffective disorder. An abundance of literature supports the use of lithium among patients with mood disorders, including those with major depressive disorder. Despite the black box warning regarding antidepressants and suicide risk among children, adolescents, and young adults, antidepressants are widely used and remain helpful in reducing suicidal thoughts and behaviors, primarily among patients with mood disorders. Treatment guidelines focus on the importance of optimizing treatment of the psychiatric conditions known to be associated with suicide risk. For patients with these conditions, the authors recommend focusing on suicide as an independent treatment target and using an enhanced medication management strategy that includes maintaining a supportive, nonjudgmental therapeutic relationship; flexibility; collaboration; measurement-based care; consideration of combining medications with nonpharmacologic, evidence-based strategies; and ongoing safety planning.

Ketamine-assisted psychotherapy in adolescents with multiple psychiatric diagnoses

Ketamine-assisted psychotherapy is a promising new treatment for a variety of mental disorders of adolescence. There is currently an adolescent mental health crisis, with a high prevalence of disorders, diagnostic complexity, and many adolescents failing to respond to conventional treatments. While there is strong evidence for the use of ketamine in adults for a variety of treatment-refractory mental illnesses, research in adolescents is in its early stages. Ketamine-assisted psychotherapy (KAP) has been described in adults with promising results and here we present the first published cases of the use of KAP in adolescents. The four cases include adolescents aged 14-19 at the initiation of treatment, each with a variety of comorbid diagnoses including treatment-resistant depression, bipolar disorder, eating disorders, anxiety, panic, and trauma-related symptoms. They each initially received sublingual ketamine, followed by sessions with intramuscular ketamine. Their courses varied, but each had symptomatic and functional improvements, and the treatment was well-tolerated. Subjective patient reports are included. Rapid resolution of symptomatology and suffering often occurs within months as the result of the application of KAP to adolescent psychiatric care but is not inevitable. Family involvement in the treatment process appears to be essential to success. The development of this modality may have a singularly positive impact that will expand the psychiatric toolbox and its healing potency.

Does route of administration affect antidepressant efficacy of ketamine? A meta-analysis of double-blind randomized controlled trials comparing intravenous and intranasal administration

Intranasal (IN) and intravenous (IV) applications of ketamine have been proven effective for the treatment of depression, but direct comparative trials or meta-analyses on whether both differ in their antidepressant efficacy are lacking. We aimed to meta-analytically compare the short-term efficacy of a single dose of IV and IN ketamine in adult patients with major depressive disorder (MDD) and included double-blind, randomized controlled trials published until February 2022 in our analyses. The main outcome was a response 24 h after the administration of a single dose of ketamine. A random-effects model was used to calculate odds ratios and confidence intervals. Differences in efficacy between intranasal and intravenous application were statistically assessed by calculating a z-test. A total of eleven studies, comprising 1340 patients, were included. Results showed, that while both IN and IV ketamine were associated with increased response rates, efficacy did not differ significantly between these routes. Heterogeneity and funnel plot asymmetry was found in the intranasal sample only. The results of the present meta-analysis corroborate the efficacy of both IN and IV application of ketamine for the treatment of MDD but suggest no difference between both routes of administration. Accordingly, future large-scale trials as well as direct comparative trials are needed to further investigate this question.

The effect of ketamine on cognition, anxiety, and social functioning in adults with psychiatric disorders: A systematic review and meta-analysis

Background

It has been shown that ketamine can improve suicidality and depression. Evidence for other dimensions of psychopathology is lacking. We undertook a systematic review to investigate the effect of ketamine on cognition, anxiety, quality of life, and social functioning in adults with psychiatric disorders.

Methods

PubMed (Medline), Scopus, PsycINFO, and EMBASE were searched up to April 2022. Randomized controlled trials (RCTs) on ketamine [or its S (+) enantiomer] reporting data on cognition, anxiety, quality of life, social functioning in adults with psychiatric disorders were included. Standardized mean difference (SMD) was used for summarizing continuous outcomes.

Results

Twenty-two reports were included in the final selection, of which 20, corresponding to 1,298 participants, were included in the quantitative synthesis. Affective disorders were the predominant diagnostic category. Median follow-up time was 21 days. The evidence was rated moderate to very low. In most trials, ketamine was administered intravenously or as adjuvant to electro-convulsant therapy (ECT). Only 2 trials of intranasal esketamine were identified. The effect of ketamine on depression was confirmed (SMD: -0.61 [95% CI: -1.06; -0.16]). Furthermore, by pooling results of 6 RCTs, ketamine may be effective in reducing anxiety symptoms (SMD: -0.42 [95% CI: -0.84; 0.003]), particularly when administered not within ECT (5 trials; SMD: -0.58 [95% CI: -1.07; -0.09]). However, there was moderate heterogeneity of results. Patients treated with ketamine also had an improvement in social functioning (SMD: -0.31 [95% CI: -0.52; -0.10]), although the estimate was based only on 2 studies. No difference to comparators was found with respect to cognition and quality of life.

Conclusion

Alongside the antidepressant effect, ketamine may also improve anxiety and social functioning in adults with affective disorders.

Key considerations for the use of ketamine and esketamine for the treatment of depression: focusing on administration, safety, and tolerability

INTRODUCTION

Racemic ketamine, a derivative of phencyclidine, has been used as a dissociative anesthetic since 1970. In 2000, the first randomized controlled trial showed a rapid relief of depressive symptoms. Since then, intravenous ketamine and intranasal S-ketamine have been validated for the treatment of depression and suicidal ideation following dose-response and double-blind placebo-controlled clinical trials. In clinical practice, after dose titration and with repeated treatments, patients may experience approximately 2-3 weeks of symptomatic relief from depression.

AREAS COVERED

Areas covered in this narrative review include mechanism of action, dosing, safety, and tolerability. Some attention is paid to the possibility of R-ketamine as a future antidepressant.

EXPERT OPINION

We recommend further investigation into treatment dosing and frequency strategies as well as approaches that prolong the therapeutic effects. The current fixed dosing of esketamine for obese individuals may be insufficient. Additional investigation into co-administration with somatic and neuromodulation treatments needs investigation. Finally, continuing to monitor research subjects and patients long-term for the emergence of adverse effects on cognition or other organ systems is critical.

Safety, effectiveness and tolerability of sublingual ketamine in depression and anxiety: A retrospective study of off-label, at-home use

Intravenous and intranasal ketamine have been shown to be effective therapeutic options in patients suffering from treatment-resistant depression (TRD). The use of sublingual (SL), rapid dissolve ketamine tablets (RDT) offers a novel approach for delivery for mental health indications. This study assessed the effectiveness and safety of self-administration of off-label, SL, rapid dissolve ketamine tablets (RDT) at-home for depression and anxiety. Intake scores on the Generalized Anxiety Disorder Screener (GAD-7) and Patient Health Questionnaire (PHQ-9) were compared to scores after treatments of three doses of ketamine RDT, and after six doses of ketamine RDT. After three doses of SL ketamine, 47.6% of patients showed a significant decrease in PHQ-9 scores, and 47.6% of patients showed a significant reduction in GAD-7 scores. Reduction rates were higher in those patients who completed a clinically recommended six doses of RDT ketamine. This study demonstrates that SL ketamine is a novel, safe, and effective treatment for TRD and treatment-resistant anxiety. SL ketamine offers an alternative therapeutic approach to IV ketamine when treating those with TRD.

Holding on or letting go? Patient experiences of control, context, and care in oral esketamine treatment for treatment-resistant depression: A qualitative study

BACKGROUND

Ketamine and its enantiomer esketamine represent promising new treatments for treatment-resistant depression (TRD). Esketamine induces acute, transient psychoactive effects. How patients perceive esketamine treatment, and which conditions facilitate optimal outcomes, remains poorly understood. Understanding patient perspectives on these phenomena is important to identify unmet needs, which can be used to improve (es)ketamine treatments.

AIMS

To explore the perspectives of TRD patients participating in "off label" oral esketamine treatment.

MATERIALS AND METHODS

In-depth interviews were conducted with 17 patients (11 women) after a six-week, twice-weekly esketamine treatment program, and subsequently after six months of at-home use. Interviews explored participants' perspectives, expectations, and experiences with esketamine treatment. Audio interviews were transcribed verbatim and analysed following an Interpretative Phenomenological Analysis (IPA) framework.

RESULTS

Key themes included overwhelming experiences; inadequate preparation; letting go of control; mood states influencing session experiences; presence and emotional support, and supportive settings. Patients' attempts to let go and give into vs. attempts to maintain control over occasionally overwhelming experiences was a central theme. Multiple factors influenced patients' ability to give into the experience and appeared to impact their mood and anxiety about future sessions, including level of preparation and education, physical and emotional support, and setting during the session.

CONCLUSION

Better preparation beforehand, an optimized treatment setting, and emotional and psychological support during (es)ketamine sessions can help patients to "let go" and may lead to better quality of care and outcomes. Recommendations to improve quality of patient care in (es)ketamine treatment are provided, including suggestions for the training of nurses and other support staff.

Case report: Intranasal esketamine for severe major depressive disorder with psychotic features

INTRODUCTION

About one third of patients with major depressive disorder (MDD) have treatment resistant depression (TRD). The difficulty of treating TRD especially in those with suicidal ideation and psychotic features demands treatments that are fast-acting, safe, and effective. Limited access, lack of viable options, and incomplete characterization of rapid-acting antidepressants has prevented widespread incorporation into treatment of patients with TRD. However, ketamine and its variations have shown promise of being effective treatment options for patients with TRD with psychotic features.

CASE DESCRIPTION

This 28-year-old patient with TRD with psychotic features received 14 treatments of intranasal esketamine over a 3-month period. This patient initially presented with anhedonia, difficulty sleeping, suicidal thoughts, and auditory hallucinations. The Quick Inventory of Depressive Symptomology (QIDS) was used to assess depression before each session.

RESULTS

After her first two treatment sessions within a week, this patient experienced a reduction in depression from severe to moderate according to the QIDS. Over 14 sessions, she had no significant adverse effects, including no psychotic symptoms during esketamine treatment, and was stabilized to mild depression without suicidal ideations. One year after treatment, she continues to be stable. She has not had auditory hallucinations since the esketamine treatment.

CONCLUSIONS

This case report provides an example of a patient with severe TRD with psychotic features that showed significant improvement after treatment with intranasal esketamine. Larger studies are indicated to further elucidate the effectiveness and safety of intranasal esketamine, so it can be more widely used for patients with TRD with psychotic features.

The putative role of the relaxin-3/RXFP3 system in clinical depression and anxiety: A systematic literature review

The relaxin-3/RXFP3 system is one of several neuropeptidergic systems putatively implicated in regulating the behavioural alterations that characterise clinical depression and anxiety, making it a potential target for clinical translation. Accordingly, this systematic review identified published reports on the role of relaxin-3/RXFP3 signalling in these neuropsychiatric disorders and their behavioural endophenotypes, evaluating evidence from animal and human studies to ascertain any relationship. We searched PubMed, EMBASE, PsycINFO and Google Scholar databases up to February 2021, finding 609 relevant records. After stringent screening, 51 of these studies were included in the final synthesis. There was considerable heterogeneity in study designs and some inconsistency across study outcomes. However, experimental evidence is consistent with an ability of relaxin-3/RXFP3 signalling to promote arousal and suppress depressive- and anxiety-like behaviour. Moreover, meta-analyses of six to eight articles investigating food intake revealed that acute RXFP3 activation had strong orexigenic effects in rats. This appraisal also identified the lack of high-quality clinical studies pertinent to the relaxin-3/RXFP3 system, a gap that future research should attempt to bridge.

Gut Hormones as Potential Therapeutic Targets or Biomarkers of Response in Depression: The Case of Motilin

Recent research has identified the gut–brain axis as a key mechanistic pathway and potential therapeutic target in depression. In this paper, the potential role of gut hormones as potential treatments or predictors of response in depression is examined, with specific reference to the peptide hormone motilin. This possibility is explored through two methods: (1) a conceptual review of the possible links between motilin and depression, including evidence from animal and human research as well as clinical trials, based on a literature search of three scientific databases, and (2) an analysis of the relationship between a functional polymorphism (rs2281820) of the motilin (MLN) gene and cross-national variations in the prevalence of depression based on allele frequency data after correction for potential confounders. It was observed that (1) there are several plausible mechanisms, including interactions with diet, monoamine, and neuroendocrine pathways, to suggest that motilin may be relevant to the pathophysiology and treatment of depression, and (2) there was a significant correlation between rs2281820 allele frequencies and the prevalence of depression after correcting for multiple confounding factors. These results suggest that further evaluation of the utility of motilin and related gut peptides as markers of antidepressant response is required and that these molecular pathways represent potential future mechanisms for antidepressant drug development.