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Theta burst stimulation (TBS) is a promising therapy for treatment-resistant major depressive disorder (MDD), but a significant proportion of individuals do not respond adequately, necessitating alternative approaches. This study explores whether individuals meeting minimum recommended physical activity levels demonstrate better responses to TBS compared to physically inactive individuals. Using data from a randomized controlled trial (n = 43), participants were categorized as physically active or inactive based on baseline International Physical Activity Questionnaire (IPAQ) scores. Depression scores (Hamilton Rating Scale for Depression, 17-item; HRSD-17) were assessed at baseline, 4, and 6 weeks of TBS treatment. A significant Time X Group effect adjusted for age and baseline depression was observed. Physically active individuals consistently exhibited lower depression scores across time points. At 4 and 6 weeks, there was a significant increase in between-group differences, indicating that the physically active group derived greater benefits from treatment. At 6 weeks, a significantly higher proportion of responders (≥50 % HRSD-17 reduction) were observed in the physically active compared to inactive group. Physical activity significantly contributed to regression and logistic models predicting treatment response. These findings support the potential role of baseline physical activity in enhancing TBS therapy for MDD.

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Ketamine has recently been shown to be non-inferior to electroconvulsive therapy (ECT), one of psychiatry's most effective treatments for depression. Given the novelty of ketamine as well as its interventional nature, ketamine is currently viewed as an alternative to ECT and as such, considered a third-line agent for treatment-refractory depression. However, available data suggest that ketamine carries a low side-effect burden and is better tolerated than many second-line augmentation strategies for depression. With this combination of higher efficacy and lower side-effect burden in conjunction with what is known about treatment outcomes in relation to the duration of untreated illness, it is in the best interest of patients for the field of psychiatry to evaluate ketamine as a second-line augmentation strategy for refractory depression.

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BACKGROUND: Treatment outcomes of patients who had received T-PEMF as an augmenting therapy at Aalborg University Hospital, Aalborg, Denmark, was evaluated. METHODS: Patients diagnosed with unipolar depression or bipolar disorder who had received a self-administered 8-week T-PEMF series between November 2019 and April 2023 were included. Data were retrieved from the patients' records. The primary outcome was the Hamilton Rating Scale for Depression 17-item version (HAMD17), both as a continuous measure and with proportions of response and remission reported. RESULTS: A total of 57 patients (65.1 % females, 86.0 % unipolar depression, mean age, 48 ± 14 years) were included. Duration of current depressive episode was almost equally divided for <2 years (38.6 %), 2-5 years (38.6 %) and > 5 years (22.8 %). HAM-D17 decreased significantly from baseline (20.8 (SD: 3.3)) to week 8 (14.5 (SD: 6.2), p < 0.001). An episode duration of 2-5 years was associated with lower odds of response on HAM-D6 (adjusted OR = 0.15, 95 % CI: 0.03; 0.96, p < 0.05) and self-rated HAM-D6 (adjusted OR = 0.09, 95 % CI: 0.01; 0.99, p = 0.05) when compared to an episode duration <2 years. LIMITATIONS: This study is limited by a lack of a control group, limited controlling of confounders, small sample sizes, and an attrition rate of 29.8 % for the primary outcome. CONCLUSION: T-PEMF reduced depressive symptoms in a real-world clinical setting including patients with both unipolar depression and bipolar disorder. Receiving T-PEMF within the first 2 years of the depressive episode was associated with an improved outcome.

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OBJECTIVE: ESKALE is a French, multicentre, observational study of adults with treatment-resistant depression (TRD) treated with esketamine. This interim analysis describes baseline demographic and clinical characteristic evolution in patients included and treated from early access program to post-marketing launch. METHODS: Data were collected from medical records and included patient characteristics, disease history at esketamine initiation, use of neurostimulation, the patient's care pathway, and the number of antidepressant treatment lines prescribed prior to esketamine initiation. Descriptive statistics were used for each cohort: the early access program 'Temporary Authorisation for Use' (ATU), post-ATU, and post-launch cohorts. RESULTS: The overall ESKALE cohort (N = 160 included; n = 157 treated with esketamine; average age 49.0 years; 66.2% female) demonstrated moderate-to-severe depression according to clinical assessment and a mean Montgomery-Åsberg Depression Rating Scale score of 32.6 (8.0); however, severity, subtype, and comorbidities were heterogeneous across the cohorts. Earlier use of esketamine and prior to alternative treatments occurred during the later cohorts. CONCLUSION: These findings demonstrated a high burden of TRD in these patients and that esketamine is used in TRD treatment regardless of their disease severity, subtype, or existing comorbidities. These results also suggest that esketamine is potentially a clinically useful alternative treatment, particularly with healthcare professionals gaining greater familiarity with and easier access to esketamine.

ESKALE is a long-term, French, multicentre, observational study based on secondary data in adult patients with treatment-resistant depression (TRD) who initiated esketamine treatment in one of three mutually exclusive cohorts: the Temporary Authorisation for Use (ATU), post-ATU, and post-launch cohorts.ESKALE is one of the largest European real-world studies investigating the profiles of more than 150 patients and their treatment with esketamine before and after marketing authorisation.A majority of patients had moderate to severe TRD, with multiple treatment failures with medications and/or neurostimulation prior to esketamine initiation.Esketamine nasal spray administration was undertaken more frequently in an outpatient setting, with the post-administration period monitoring being undertaken mostly by nurses.Esketamine was used in patients with TRD in real-world conditions regardless of their disease severity and subtype or existing comorbidities.These results highlight both the need for an effective treatment for TRD and the adoption of esketamine by multidisciplinary teams that are involved in esketamine prescription and administration.

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BACKGROUND: Persons with Major Depressive Disorder (MDD), notably treatment-resistant depression (TRD), are differentially affected by type 2 diabetes mellitus and associated morbidity. Ketamine is highly efficacious in the treatment of adults living with MDD, notably TRD. Herein, we sought to determine the effect of ketamine on metabolic parameters in animal stress paradigms and human studies. METHODS: We performed a comprehensive search on PubMed, OVID, and Scopus databases for primary research articles from inception to May 5, 2024. Study screening and data extraction were performed by two reviewers (S.W. and G.H.L.). Both preclinical and clinical studies were included in this review. RESULTS: Results from the preclinical studies indicate that in experimental diabetic conditions, ketamine does not disrupt glucose-insulin homeostasis. Within adults with MDD, ketamine is associated with GLUT3 transporter upregulation and differentially affects metabolomic signatures. In adults with TRD, ketamine induces increased brain glucose uptake in the prefrontal cortex. Available evidence suggests that ketamine does not adversely affect metabolic parameters. LIMITATIONS: There are a paucity of clinical studies evaluating the effects of ketamine on glucose-insulin homeostasis in adults with MDD. CONCLUSIONS: Our results indicate that ketamine is not associated with significant and/or persistent disruptions in metabolic parameters. Available evidence indicates that ketamine does not adversely affect glucose-insulin homeostasis. These results underscore ketamine's efficacy and safety as an antidepressant treatment that is not associated with metabolic disturbances commonly reported with current augmentation therapies.

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Accelerated repetitive transcranial magnetic stimulation (rTMS) is a promising treatment for treatment-resistant depression (TRD). We aimed to investigate the existence of clinical predictive factors in response to accelerated rTMS in the treatment of TRD. In total, 119 TRD patients who received accelerated rTMS were included in this study. The stimulation protocol was 15 Hz stimulation over the the left dorsolateral prefrontal cortex. The protocol consisted of 25 sessions, each session lasting 30 min for a total of 3000 pulses. Five sessions were applied per day for 5 consecutive days. At baseline (T0), day 5 (immediately after treatment) (T1), 4 weeks after treatment (T2), depression severity was evaluated using the 17-item Hamilton Depression Rating Scale (HAMD-17), cognitive function was evaluated using Wisconsin Card Sorting Test (WCST), the intensity of suicidal ideation was evaluated using the Columbia-Suicide Severity Rating Scale (C-SSRS). Systemic immune-inflammation index (SII) was calculated at T0 and T2. The HAMD-17 scores, WCST performance, the C-SSRS scores at T1 and T2 were improved from T0 (P < 0.01). The SII at T2 was lower than at T0 (P < 0.01). The response rates at T1 and T2 were 57.98% (69/119) and 48.74% (58/119), respectively. The results of binary logistic analysis showed that shorter course of depression, two failed antidepressant trials, no history of ECT treatment, and lower levels of SII were predictive factors for accelerated rTMS treatment response at T1 and T2 (P < 0.05), while not having a history of hospitalization was a predictive factor for response at T2 (P < 0.05) but not at T1 (P > 0.05). Based on ROC curve analysis, the optimal cut-off values of SII for discriminating responders from non-responders at T1 and T2 were < 478.56 and < 485.03, respectively. The AUC of SII at T0 predicting response for T1 and T2 were 0.729 and 0.797. We found several clinical predictors of better responses to the accelerated rTMS. Identifying clinical predictors of response is relevant to personalize and adapt rTMS protocols in TRD patients.

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BACKGROUND: Electroconvulsive therapy (ECT) is a commonly used alternative for treatment-resistant depression (TRD). Although esketamine has a rapid pharmacological antidepressant action, it has not been studied as an ECT anesthetic. The objective of this study was to compare the efficacy and safety of esketamine with propofol when both are used as ECT anesthetic agents. METHODS: Forty patients with TRD were assigned to one of two arms in a double-blind, randomized controlled trial: esketamine or propofol anesthesia for a series of eight ECT sessions. Using a non-inferiority design, the primary outcome was the reduction in HAMD-17 depressive symptoms. The other outcomes were: rates of response and remission, anxiety, suicidal ideation, cognitive function, and adverse events. These were compared in an intention-to-treat analysis. RESULTS: Esketamine-ECT was non-inferior to propofol-ECT for reducing TRD symptoms after 8 sessions (adjusted Δ = 2.0, 95 % CI: -1.2-5.1). Compared to propofol-ECT, esketamine-ECT also had higher depression response (80 % vs. 70 %; p = .06) and remission (65 % vs. 55 %; p = .11) rates but non-inferiority was not established. In four components of cognitive function (speed of processing, working memory, visual learning, and verbal learning) esketamine-ECT was non-inferior to propofol-ECT. The results for anxiety, suicidal ideation, and adverse events (all p's > .05) were inconclusive. CONCLUSION: Esketamine was non-inferior to propofol when both are used as anesthetics for TRD patients undergoing ECT. Replication studies with larger samples are needed to examine the inconclusive results. REGISTRATION NUMBER: ChiCTR2000033715.

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Background: Although there are many treatment options available for depression, a large portion of patients with depression are diagnosed with treatment-resistant depression (TRD), which is characterized by an inadequate response to antidepressant treatment. Identifying the TRD population is crucial in terms of saving time and resources in depression treatment. Recently several studies employed various methods on EEG datasets for automatic depression detection or treatment outcome prediction. However, no previous study has used the deep learning (DL) approach and EEG signals for detecting treatment resistance. Method: 77 patients with TRD, 43 patients with non-TRD, and 40 healthy controls were compared using GoogleNet convolutional neural network and DL on EEG data. Additionally, Class Activation Maps (CAMs) acquired from the TRD and non-TRD groups were used to obtain distinctive regions for classification. Results: GoogleNet classified the healthy controls and non-TRD group with 88.43%, the healthy controls and TRD subjects with 89.73%, and the TRD and non-TRD group with 90.05% accuracy. The external validation accuracy for the TRD-non-TRD classification was 73.33%. Finally, the CAM analysis revealed that the TRD group contained dominant features in class detection of deep learning architecture in almost all electrodes. Limitations: Our study is limited by the moderate sample size of clinical groups and the retrospective nature of the study. Conclusion: These findings suggest that EEG-based deep learning can be used to classify treatment resistance in depression and may in the future prove to be a useful tool in psychiatry practice to identify patients who need more vigorous intervention.

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Major depressive disorder (MDD) is a highly prevalent psychiatric disorder, associated with substantial burden and large economical costs. Notwithstanding various conventional antidepressant treatment options, a large portion of depressed people (ca. 30%) fails to respond to first-line treatment, resulting in treatment-resistant depression (TRD). Although non-response to multiple antidepressant interventions is a common outcome, a consensus definition of TRD is not yet available. In practice, TRD is applied when two or more successive treatments with different antidepressants are not working. The last decade's intense research into new medicines for TRD has led to two developments, using typical or serotonergic (psilocybin, ayahuasca) and atypical (glutamatergic) psychedelics (ketamine, esketamine). Both approaches, although via different entrance mechanism, exhibit a fast onset but also long-lasting antidepressant effect far beyond the biological presence of the drug in the body, strongly indicating that downstream mechanisms activated by signaling cascades in the brain are involved. The present chapter describes the clinical development of psilocybin and esketamine for TRD and discusses the problems involved in the use of a proper placebo because of the psychotomimetic (psilocybin) or dissociative (ketamine) effects that interfere with performing "blind" studies. Nevertheless, intranasal esketamine was developed and approved for TRD, whereas psilocybin has shown positive results. Adverse effects and tolerability of both drugs in the dose ranges used are generally acceptable. The emergence of anti-TRD medicines for treatment of a very severe disease is a breakthrough in psychiatry.

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Major depressive disorder (MDD) is a psychiatric disorder with several effective therapeutic approaches, being antidepressants and psychotherapies the first-line treatments. Nonetheless, due to side effects, limited efficacy, and contraindications for these treatments, alternative treatment options are required. Neurostimulation is a non-pharmacological and non-psychotherapeutic approach that has been under study for diverse neuropsychiatric conditions in the form of electrical or magnetic stimulation of the brain. Repetitive transcranial magnetic stimulation (rTMS) is a neurostimulation method designed to generate magnetic fields and deliver magnetic pulses to stimulate the brain cortex. The magnetic pulses produce electrical currents in the brain which are not intense enough to provoke seizures, differentiating this method from other forms of neurostimulation that produce seizures. Although the exact rTMS mechanisms of action are not completely understood, rTMS seems to cause its beneficial effects through changes in neuroplasticity. Devices and protocols for rTMS are still evolving, becoming more efficient over time. There are still some challenges to be addressed, including further refinement of parameters (coil/device type, location, intensity, frequency, number of sessions, and duration of treatment); treatment cost and burden for patients; and treatment resistance. However, the efficacy, tolerability, and safety of some rTMS protocols have been demonstrated in different double-blind sham-controlled randomized controlled trials and meta-analyses for treatment-resistant depression.

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In this chapter, we explore the historical evolution, current applications, and future directions of Deep Brain Stimulation (DBS) for Treatment-Resistant Depression (TRD). We begin by highlighting the early efforts of neurologists and neurosurgeons who laid the foundations for today's DBS techniques, moving from controversial lobotomies to the precision of stereotactic surgery. We focus on the advent of DBS, emphasizing its emergence as a significant breakthrough for movement disorders and its extension to psychiatric conditions, including TRD. We provide an overview of the neural networks implicated in depression, detailing the rationale for the choice of common DBS targets. We also cover the technical aspects of DBS, from electrode placement to programming and parameter selection. We then critically review the evidence from clinical trials and open-label studies, acknowledging the mixed outcomes and the challenges posed by placebo effects and trial design. Safety and ethical considerations are also discussed. Finally, we explore innovative directions for DBS research, including the potential of closed-loop systems, dual stimulation strategies, and noninvasive alternatives like ultrasound neuromodulation. In the last section, we outline recommendations for future DBS studies, including the use of alternative designs for placebo control, the collection of neural and behavioral recordings, and the application of machine-learning approaches.

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Many clinicians choose psychoanalytic psychotherapy or supportive psychotherapy as the primary method of treating depression with or without antidepressant medications. Despite new antidepressants, 20% or more patients showed inadequate responses to the medications, and remained in chronic courses, known as "treatment-resistant depression (TRD)."In this chapter, we described (1) the reasons for psychotherapy in treating TRD from the perspectives of the hazard of polypharmacy, resistance, and neural mechanisms. (2) Next, we focused on the importance of assessment with two clinical vignettes and the original modality of psychoanalysis, psychoanalytic psychotherapy, and supportive psychotherapy in brief. (3) Finally, we described specific considerations in undertaking psychotherapy for TRD patients in terms of transference, countertransference, and resistance. In addition, the efficacy of psychoanalytic psychotherapy in childhood, adolescent, and late-life depression has been depicted in this paper.

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Randomized controlled trials have reported psychoanalytic psychotherapy to improve longer-term post-treatment outcomes in patients with treatment-resistant depression. In this case study, we examine the therapy process of a female trial participant diagnosed with treatment-resistant depression. Structured clinical assessments indicated that the patient's level of depression remained unchanged during and after treatment. Over the course of the therapy, she repeatedly broke away from important others and finally also from the therapy itself, which we linked to the impact of earlier experiences of abandonment on her internal world. In the discussion, we present a variety of reflections that were put forward by the authors during a series of case discussion meetings. Some of these reflections relate to how the inner world of this patient might have triggered a negative therapeutic reaction and a destructive pattern of repetition. The interpretative stance, in which the therapist interpreted this reaction as indicative of a psychic conflict and linked this conflict to the therapeutic relationship, seemed to be experienced by the patient as unhelpful and persecutory. Other elements that were brought up include basic distrust, lack of symbolization and trauma in the patient, as well as the constraints of the research context.

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Understanding why some patients with depression remain resistant to antidepressant medication could be elucidated by investigating their associated neural features. Although research has consistently demonstrated abnormalities in the anterior cingulate cortex (ACC) - a region that is part of the default mode network (DMN) - in treatment-resistant depression (TRD), a considerable research gap exists in discerning how these neural networks distinguish TRD from treatment-sensitive depression (TSD). We aimed to evaluate the resting-state functional connectivity (rsFC) of the ACC with other regions of the DMN to better understand the role of this structure in the pathophysiology of TRD. 35 TRD patients, 35 TSD patients, and 38 healthy controls (HC) underwent a resting-state functional MRI protocol. Seed-based functional connectivity analyses were performed, comparing the three groups for the connectivity between two subregions of the ACC (the subgenual ACC (sgACC) and the rostral ACC (rACC)) and the DMN (p < 0.05 FWE corrected). Furthermore, inter-network connectivity of the DMN with other neural networks was explored by independent component (ICA) analyses (p < 0.01, FDR corrected). The results demonstrated hyperconnectivity between the rACC and the posterior cingulate cortex in TRD relative to TSD and HC (F(2,105) = 5.335, p < 0.05). ICA found DMN connectivity to regions of the visual network (TRDTSD), differentiating the two clinical groups. These results provide confirmatory evidence of DMN hyperconnectivity and preliminary evidence for its interactions with other neural networks as key neural mechanisms underlying treatment non-responsiveness.

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BACKGROUND: Immune dysregulation can play a role in depression pathophysiology, and immunological antagonists can improve depressive symptoms in treatment-resistant bipolar depression (TRD) patients according to studies. OBJECTIVE: To evaluate the anti-depressant effects of the anti-inflammatory drug, pentoxifylline (PTX) in TRD bipolar I/II adult subjects. METHODS: This 12-week, randomized, double-blind, placebo-controlled, parallel-group trial of 60 participants was conducted at Hawler Psychiatric Hospital and Private Clinic in Erbil, Iraq. Participants were confirmed as being qualified for bipolar I/II depression based on DSM-5 criteria. Data were analyzed using modified intent-to-treat analysis. RESULTS: There were no significant differences between the two groups in Hamilton Rating Scale for Depression-17 (HAM-D-17) scores (χ2=1.9, P =.48) or a significant time × treatment interaction (χ2=7.1, P=.54). Nevertheless, a significant effect of time was observed with both groups' reduction in HAM-D-17 scores from the start to the endpoint (χ2= 2.11, P=.002). Besides, a significant time × treatment × CRP interaction was found (χ2=3.1, P=0.016), where there was more reduction in HAM-D-17 score in PTX-treated subjects with CRP> 7.1 mg/L. The response rate difference between PTX and the placebo group did not reach a significance level (χ2=0.84, p=0.43). Furthermore, serum concentrations of TNF-α, CRP, and IL-6 significantly reduced at week 12 in the PTX group (P=.007,.04, and <.001, respectively). CONCLUSION: The current proof of concept study found that in terms of overall anti-depressant effectiveness in bipolar patients with TRD, PTX is not superior to placebo. However, it may improve depressive mood in a subpopulation of subjects with a higher pretreatment inflammatory profile.

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Background: The psychiatric needs of those with cancer and other advanced illnesses are becoming increasingly recognized. Ketamine is emerging as a promising treatment option for depressive disorders in psychiatric and palliative care. In the palliative care setting, its study has been hindered by lack of consistent administration routes and dosing. Intranasal (IN) esketamine (Spravato®) has recently received U.S. Food and Drug Administration (FDA) approval as an adjunctive agent for treatment-resistant depression (TRD) and major depressive disorder (MDD) with suicidal ideation (SI). Objective: We sought to offer IN esketamine to patients suffering from TRD and SI at a comprehensive cancer center. Methods: We designed and implemented a protocol to administer IN esketamine and describe three cases in which it was provided to patients with TRD and SI at a palliative care clinic in the United States. Results: Following treatment, all three patients had substantial reduction in depression severity and no further suicidalideation. These improvements were maintained for up to a year. No serious adverse events occurred. Conclusions: These cases illustrate the potential utility of IN esketamine in the palliative care setting.

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BACKGROUND: Treatment-resistant depression (TRD) is defined as the failure of at least two antidepressants in adequate doses and timing during a major depressive episode. Esketamine intranasal (ESK-IN) has been approved by the Food and Drug Administration and the European Medicines Agency for the treatment of TRD in combination with other antidepressants. AIMS: To assess the effectiveness and tolerability of a sample of TRD patients who received treatment with ESK-IN as part of the compassionate use program. METHODS: A retrospective, observational study was carried out on patients with a diagnosis of TRD enrolled in the early access program of ESK-IN in nine centers. Effectiveness was assessed with the Montgomery-Asberg depression rating scale (MADRS) at four time points: baseline, 28, 90, and 180 days of treatment. RESULTS: The sample included 71 patients (70% women) with a mean baseline MADRS score of 38.27 ± 5.9 and total or partial work disability rates of 85%. ESK-IN treatment was associated with a statistically and clinically significant reduction in the severity of depressive symptoms at all time points assessed. The presence of side effects was common but the majority were mild in severity and resolved after the observation period. Those patients who received psychotherapy in combination with ESK-IN showed a significantly lower MADRS score at 90 and 180 days than those patients who did not undergo psychotherapy. CONCLUSION: ESK-IN has proven to be effective and safe in a clinical sample of patients with severe TRD. To optimize clinical outcomes, the pharmacological treatment for TRD should always be integrated into a comprehensive therapeutic plan that encompasses strategies such as psychotherapy, social support, and family interventions.

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OBJECTIVE: To describe the quality of life and clinical characteristics of treatment-resistant depression (TRD) patients in an Australian patient cohort recruited cross-sectionally during admission. METHOD: Inpatients admitted for TRD treatment completed a quality of life questionnaire (AQoL-8D) and a depression severity assessment (HAM-D). A chart review and patient interview occurred for demographic and patient characteristics. Comparisons between the mean AQoL-8D scores of the study population and Australian population norms occurred. RESULTS: 79 TRD inpatients (70.9% female), mean age of 44.8 ± 14.9 years, were recruited, with 78.5% having an anxiety disorder, 48.1% post-traumatic stress disorder, and 30.4% a personality disorder. Adjunctive to antidepressants, 92.4% were taking antipsychotics and 55.7% were taking mood stabilisers. Approximately 42% of patients received transcranial magnetic stimulation, and 35.4% received electroconvulsive therapy. Mean HAM-D score was 20.3 ± 5.2, and AQoL-8D score (120.1 ± 16.5) was significantly higher than Australian population norms (p < .001) indicating reduced quality of life. CONCLUSIONS: Personal and clinical characteristics of patients hospitalised for TRD were similar to TRD globally with impaired quality of life relative to the general Australian population. TRD patients on average presented with moderate/severe depression, highlighting the need for greater support for these individuals.

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AIM: Although the antidepressant effect of ketamine on treatment-resistant depression (TRD) has been frequently reported in North American and European countries, evidence is scarce among the Asian population. We aimed to evaluate the efficacy and safety of intravenous ketamine in Japanese patients with TRD. METHODS: In this double-blind randomized placebo-controlled trial, 34 Japanese patients with TRD were randomized to receive either intravenous ketamine (0.5 mg/kg) or placebo, administered over 40 min, twice a week, for 2 weeks. The primary outcome was the change in the Montgomery Åsberg Depression Rating Scale (MADRS) total score from baseline to post-treatment. Secondary outcomes included changes in other depressive symptomatology scores and remission, response, and partial response rates. We also examined the association between baseline clinical demographic characteristics and changes in the MADRS total score. RESULTS: Intention-to-treat analysis indicated no significant difference in the decrease in MADRS total score between the groups (-8.1 ± 10.0 vs -2.5 ± 5.2, t[32] = 2.02, P = 0.052), whereas per-protocol analysis showed a significant reduction in the ketamine group compared to the placebo group (-9.1 ± 10.2 vs -2.7 ± 5.3, t[29] = 2.22, P = 0.034). No significant group differences were observed in other outcomes. Adverse events were more frequent in the ketamine group than in the placebo group, and no serious adverse events were reported. A higher baseline MADRS total score and body mass index were associated with a greater reduction in the MADRS total score. CONCLUSION: Intravenous ketamine outperformed placebo in Japanese patients with TRD who completed the study, suggesting that ketamine could alleviate depressive symptoms of TRD across diverse ethnic populations.