Published papers

Objective: Schizophrenia in general is notoriously associated with relapses rendering the illness progressive to worse outcomes, a concept of which is compatible with neurotoxicity. Therefore, relapse prevention is of utmost clinical relevance. Methods: In this review, we aim to put relapse into clinical context in the realm of natural history of, or heterogeneity in, schizophrenia and summarize risk factors of relapse. We discuss how to effectively 'define' relapse in schizophrenia and recent meta-analytic studies on this topic to highlight the importance of continuous antipsychotic treatment. Results: The following issues emerged: 'How low maintenance antipsychotic dosage could be?', 'How extended dosing could be?', 'Who could be successfully withdrawn from antipsychotics?' and 'How relapse could be defined in the first place?' The question in particular is how better to deliver antipsychotics at the lowest possible, whereby dose and dosing interval are relevant. While ongoing antipsychotic treatment is the rule, recent works are pointing to a possibility of lower dosage in the maintenance phase of the illness. Conclusions: Bearing in mind that suboptimal adherence and withdrawal from antipsychotics are an established and unequivocal risk factor for relapse, further investigations are certainly needed to explore user-friendly manner of psychopharmacotherapy to prevent relapse in schizophrenia.

Pharmacological treatments of psychiatric illness have been developed and many psychotropic drugs are now on the market. The body of safety information regarding psychotropic agents is so large that it is difficult for clinicians to consider all the details of possible adverse drug reactions(ADRs) in daily clinical practice. Although it is impossible to predict and prevent all occurrences of ADRs, many of them may be preventable. In this context, there is a strong need for compact manuals of diagnosis and treatment for ADRs arising from psychotropic agents that are likely to be used in daily practice. Under the auspices of the Japanese Society of Psychiatry and Neurology, a task force was convened to answer this need. This review focuses on the general considerations of ADRs with psychotropic agents, based on discussions of the task force. We also discuss the guidelines for drug safety monitoring, targeted towards specific psychiatric disorders or patients taking specific classes of drugs. Finally, we introduce the Adverse Drug Reactions Relief System in Japan.

Self-disturbance is considered a core feature underlying the psychopathology of schizophrenia. Interoception has an important role in the development of a sense of self, leading to increased interest in the potential contribution of abnormal interoception to self-disturbances in schizophrenia. Several neuropsychological studies have demonstrated aberrant interoception in schizophrenia. However, cortical interoceptive processing has not yet been thoroughly investigated. Thus, we sought to examine resting-state heartbeat-evoked potential (HEP) in this population. We hypothesized that patients with schizophrenia would exhibit significant alterations in HEP compared to healthy controls (HCs). In this cross-sectional electroencephalogram (EEG) study, we compared the HEPs between age- and sex-matched groups of patients with schizophrenia and HCs. A 10-min resting-state EEG with eyes closed and an electrocardiogram (ECG) were recorded and analyzed for the time window of 450 ms to 500 ms after an ECG R peak. A positive HEP shift was observed in the frontal-central regions (F [1, 82] = 7.402, p = 0.008, partial η2 = 0.009) in patients with schizophrenia (n = 61) when compared with HCs (n = 31) after adjusting for confounders such as age, sex, and heart rate. A cluster-based correction analysis revealed that the HEP around the right frontal area (Fp2, F4, and F8) showed the most significant group differences (F [1, 82] = 10.079, p = 0.002, partial η2 = 0.021), with a peak at the F4 electrode site (F [1, 82] = 12.646, p < 0.001, partial η2 = 0.069). We observed no correlation between HEP and symptoms in patients with schizophrenia. A positive shift of HEP during the late component could reflect a trait abnormality in schizophrenia. Further research is required to determine the association between the altered cortical interoceptive processing indexed with HEP and self-disturbances in schizophrenia.

Background: To elucidate the neurobiology underlying alcohol's effect on the human brain, we examined the acute effects of moderate alcohol administration on levels of glutamatergic neurometabolites and N-acetylaspartate, an amino acid found in neurons, may reflect disordered neuronal integrity. Methods: Eighteen healthy Japanese participants (7 males/11 females) aged 20–30 years who were heterozygous for an inactive allele of acetaldehyde dehydrogenase-2 (ALDH/*1/*2) were included. Participants underwent an intravenous alcohol infusion using the clamp method at a target blood alcohol concentration (BAC) of 0.50 mg/mL for 90 min within a range of ±0.05 mg/mL. We examined glutamate + glutamine (Glx) and N-acetylaspartate N-acetylaspartylglutamate (NAA) levels in the midcingulate cortex (MCC) using 3 T 1H-MRS PRESS at baseline, 90 min, and 180 min (i.e., 90 min after alcohol infusion was finished). A two-way repeated-measures analysis of variance was used to assess longitudinal changes in Glx and NAA levels, with time and sex as within- and between-subject factors, respectively. Pearson's correlation coefficients were calculated among neurometabolite levels and BAC or blood acetaldehyde concentration (BAAC). Results: Both Glx (F(2,32) = 8.15, p = 0.004, η2 = 0.15) and NAA (F(2,32) = 5.01, p = 0.04, η2 = 0.07) levels were increased after alcohol injection. There were no sex or time × sex interaction effects observed. NAA levels were positively correlated with BAAC at 90 min (r(13) = 0.77, p = 0.01). There were no associations between neurometabolite levels and BAC. Conclusions: Both Glx and NAA levels in the MCC increased in response to the administration of moderate concentrations of alcohol. Given positive associations between NAA levels and BAAC and the hypothetical glutamate release via dopamine pathways, the effects of drinking on the MCC in the acute phase may be ascribed to acetaldehyde metabolized from alcohol.

Quantitative susceptibility mapping is a magnetic resonance imaging technique that measures brain tissues’ magnetic susceptibility, including iron deposition and myelination. This study examines the relationship between subcortical volume and magnetic susceptibility and determines specific differences in these measures among patients with major depressive disorder (MDD), patients with schizophrenia, and healthy controls (HCs). This was a cross-sectional study. Sex- and age- matched patients with MDD (n = 49), patients with schizophrenia (n = 24), and HCs (n = 50) were included. Magnetic resonance imaging was conducted using quantitative susceptibility mapping and T1-weighted imaging to measure subcortical susceptibility and volume. The acquired brain measurements were compared among groups using analyses of variance and post hoc comparisons. Finally, a general linear model examined the susceptibility–volume relationship. Significant group-level differences were found in the magnetic susceptibility of the nucleus accumbens and amygdala (p = 0.045). Post-hoc analyses indicated that the magnetic susceptibility of the nucleus accumbens and amygdala for the MDD group was significantly higher than that for the HC group (p = 0.0054, p = 0.0065, respectively). However, no significant differences in subcortical volume were found between the groups. The general linear model indicated a significant interaction between group and volume for the nucleus accumbens in MDD group but not schizophrenia or HC groups. This study showed susceptibility alterations in the nucleus accumbens and amygdala in MDD patients. A significant relationship was observed between subcortical susceptibility and volume in the MDD group’s nucleus accumbens, which indicated abnormalities in myelination and the dopaminergic system related to iron deposition.

Antipsychotic polypharmacy (using multiple antipsychotics simultaneously) in schizophrenia appears to be a common practice in the real world. However, it has been a practice with substantial debate for its possible pros and cons. In this section, we systematically review clinical evidence on antipsychotic polypharmacy in schizophrenia. We first focus on the prevalence of antipsychotic polypharmacy in schizophrenia in the real-world clinical settings, to highlight the fact that it is becoming a frequent reality. Next, we discuss potential mechanisms that lead to such a controversial practice. Then, meta-analyses and systematic reviews that addressed the usefulness of antipsychotic polypharmacy in schizophrenia are qualitatively assessed.The results of this critical appraisal on the currently available evidence indicate that usefulness of antipsychotic polypharmacy in schizophrenia has been a focus of extensive research. However, there are practically too many possible combinations to be evaluated with each antipsychotic dosage also in mind. Evidence on antipsychotic polypharmacy currently remains equivocal at best even for polypharmacy involving clozapine; it is all the more questionable for other mode of antipsychotic combination therapy. Moreover, there has been no study that evaluated antipsychotic polypharmacy in reference with other various augmentation strategies that may potentially be effective.While a possibility cannot be denied for clinical usefulness of some mode of antipsychotic combination therapy in schizophrenia in general (e.g., combining prolactin-raising or metabolically problematic antipsychotics with more benign agents) or on an individual basis (i.e., for treatment-resistant schizophrenia), the currently available evidence supports the notion that prescribers should remain very conservative in resorting to antipsychotic polypharmacy. In other words, physicians should keep in mind the very basic of pharmacotherapy in every field of medicine; medications should be simple at least at early stages of treatment unless evidence unequivocally points to the contrary.An effort will be made to synthesize the currently available evidence to be translated into future directions on this critically relevant topic. Further, potential strategies to counteract antipsychotic polypharmacy in schizophrenia are discussed in detail. More work is clearly indicated for this important issue that will remain a matter of hot debate for the years to come.

© 2018 Elsevier B.V. Objective: The impact of subjective vs. objective illness severity on subjective cognitive impairment in patients with depression has not been addressed. Methods: This study is a post-hoc analysis of our cross-sectional study in Japanese outpatients with depressive disorder (ICD-10) (Ozawa et al., 2017). The participants received assessments with the Japanese version of the Perceived Deficits Questionnaire (J-PDQ), Quick Inventory of Depressive Symptomatology (QIDS), and Montgomery–Asberg Depression Rating Scale (MADRS). First, multiple regression analysis was conducted to examine the effects of demographic and clinical characteristics, including illness severity and medications (e.g., antidepressants and benzodiazepines), on the PDQ total score. Next, we categorized the participants into 4 groups based on the presence/absence of subjective and objective symptom remission (i.e., QIDS total score of ≤5 and MADRS total score of ≤9, respectively), and compared the differences in PDQ total scores between the QIDS- and MADRS-remitted group and the QIDS-non-remitted but MADRS-remitted group. Results: 102 participants were included (45 men; mean ± SD age, 50.5 ± 14.7 years). Higher QIDS and MADRS total scores were significantly associated with a greater PDQ total score (both p's < 0.001), while other factors did not exhibit any associations. The QIDS-non-remitted but MADRS-remitted group showed a significantly higher PDQ total score than that of the QIDS- and MADRS-remitted group (median 10.0 [8.0–12.0] vs. 3.0 [range: 2.0–4.0], p < 0.001). Conclusions: These findings suggest that objective remission in the absence of subjective remission may not be adequate to improve subjective cognitive functioning.

Aims: To investigate the acute effects of intravenous alcohol and its metabolite acetaldehyde on cognitive function in healthy individuals. Design: Experimental pre-test/post-test design. Setting: Kurihama Medical and Addiction Center, Japan. Participants: A total of 298 healthy Japanese people age 20 to 24 years. Measurements: Participants underwent an intravenous alcohol infusion with a target blood alcohol concentration (BAC) of 0.50 mg/mL for 180 minutes. Participants completed the continuous performance test (CPT) for sustained attention, the paced auditory serial addition test (PASAT) for working memory, and the reaction time test (RTT) for speed/accuracy, along with the blood test for BAC and blood acetaldehyde concentration (BAAC) at baseline, 60 and 180 minutes. Findings: Although the target BAC was maintained during the infusion, BAAC peaked at 30 minutes and then gradually declined (η2 = 0.18, P < 0.01). The CPT scores worsened, and the changes between 0 and 60 minutes were correlated with BAAC (correct detection, η2 = 0.09, P < 0.01; r = −0.34, P < 0.01; omission errors, η2 = 0.08, P < 0.01; r = 0.34, P < 0.01). PASAT scores improved through 180 minutes, whereas the changes between 0 and 60 minutes were negatively correlated with BAAC (task one, η2 = 0.02, P < 0.01; r = −0.25, P < 0.01; task two, η2 = 0.03, P < 0.01; r = −0.28, P < 0.01). Although RTTs worsened, they were not associated with BAC or BAAC. None of these comparisons maintained the time effect after controlling for body height. Conclusions: Acetaldehyde exposure following acute intravenous alcohol appears to have a negative impact on sustained attention and working memory, whereas there seems to be only a minor effect of moderate alcohol concentration on speed and accuracy.

Background: Abnormalities in the anterior cingulate cortex (ACC) are thought to play an important role in the pathophysiology of schizophrenia. Given regional variations in ACC structure, the present study aimed to examine ACC structural subdivisions and their relationships to treatment resistance and glutamatergic levels in schizophrenia. Methods: This study included 100 patients with schizophrenia and 52 healthy controls from 2 cohorts. We applied non-negative matrix factorization to identify accurate and stable spatial components of ACC structure. Between groups, we compared ACC structural indices in each spatial component based on treatment resistance or response and tested relationships with ACC glutamate + glutamine levels. Results: We detected reductions in cortical thickness and increases in mean diffusivity in the spatial components on the surface of the cingulate sulcus, especially in patients with treatment-resistant and clozapine-resistant schizophrenia. Notably, mean diffusivity in these components was higher in patients who did not respond to clozapine compared to those who did. Furthermore, these ACC structural alterations were related to elevated ACC glutamate + glutamine levels but not related to symptomatology or antipsychotic dose. Limitations: Sample sizes, cross-sectional findings and mixed antipsychotic status were limitations of this study. Conclusion: This study identified reproducible abnormalities in ACC structures in patients with treatment-resistant and clozapine-resistant schizophrenia. Given that these spatial components play a role in inhibitory control, the present study strengthens the notion that glutamate-related disinhibition is a common biological feature of treatment resistance in schizophrenia.

Aims: Develop a robust and user-friendly software tool for the prediction of dopamine D2 receptor occupancy (RO) in patients with schizophrenia treated with either olanzapine or risperidone, in order to facilitate clinician exploration of the impact of treatment strategies on RO using sparse plasma concentration measurements. Methods: Previously developed population pharmacokinetic models for olanzapine and risperidone were combined with a pharmacodynamic model for D2 RO and implemented in the R programming language. Maximum a posteriori Bayesian estimation was used to provide predictions of plasma concentration and RO based on sparse concentration sampling. These predictions were then compared to observed plasma concentration and RO. Results: The average (standard deviation) response times of the tools, defined as the time required for the application to predict parameter values and display the output, were 2.8 (3.1) and 5.3 (4.3) seconds for olanzapine and risperidone, respectively. The mean error (95% confidence interval) and root mean squared error (95% confidence interval) of predicted vs. observed concentrations were 3.73 ng/mL (−2.42–9.87) and 10.816 ng/mL (6.71–14.93) for olanzapine, and 0.46 ng/mL (−4.56–5.47) and 6.68 ng/mL (3.57–9.78) for risperidone and its active metabolite (9-OH risperidone). Mean error and root mean squared error of RO were −1.47% (−4.65–1.69) and 5.80% (3.89–7.72) for olanzapine and −0.91% (−7.68–5.85) and 8.87% (4.56–13.17) for risperidone. Conclusion: Our monitoring software predicts concentration–time profiles and the corresponding D2 RO from sparsely sampled concentration measurements in an accessible and accurate form.

The lack of biomarkers to monitor and predict the efficacy of electroconvulsive therapy (ECT) has hindered its optimal use. To establish metabolomic markers for monitoring and predicting the treatment efficacy of ECT, we comprehensively evaluated metabolite levels in patients with major depressive disorder (MDD) by performing targeted and non-targeted metabolomic analyses using plasma samples before and after the first, third, and final ECT sessions, and 3–7 days after the final session. We compared the plasma metabolomes of age- and sex-matched healthy controls (HCs). Thirteen hospitalized patients with MDD and their corresponding HCs were included in this study. We observed that patients with MDD exhibited lower levels of amino acids, including gamma-aminobutyric acid (GABA), and metabolites involved in tryptophan metabolism and the kynurenine pathway, and higher levels of cortisol at baseline. Furthermore, we investigated the relationship between metabolite levels and depression severity across seven measurement timepoints along with one correlation analysis and found that amino acids, including GABA and tryptophan catabolites, were significantly correlated with the severity of depression. Despite the exploratory nature of this study due to the limited sample size necessitating further validation, our findings suggest that the blood metabolic profile has potential as a biomarker for ECT.

Introduction There is an imminent need for faster-acting and more effective antidepressants beyond the monoaminergic hypothesis. Methods We systematically searched the US Clinical Trials registry for antidepressant compounds with completed phase II and III trials. Compounds that demonstrated significant superiority over placebo in the primary outcome measure in the latest phase of phase II and III trials were identified. The collateral information was gathered via a PubMed search and press releases. Results Nine compounds were identified. AXS-05 (a combination of dextromethorphan and bupropion) and ansofaxine hydrochloride showed a positive result over placebo in a phase III study for major depressive disorder or treatment-resistant depression. MIJ821, nitrous oxide, psilocybin, ayahuasca, facial injection of botulinum toxin A, prasterone, and casopitant demonstrated at least one positive result in phase II trials. Ayahuasca showed a greater response rate than placebo at week one, indicating the rapid antidepressant effect. Discussion These new compounds with novel mechanisms of action are expected to provide a greater variety of treatment options for depression if preliminary positive results are confirmed.

Background Regular visit to psychiatric clinic is essential for successful treatment of any psychiatric condition including attention-deficit/hyperactivity disorder (AD/HD). However, cancellation of outpatient appointments in patients with AD/HD, which represents a significant medical loss, has not been systematically investigated to our knowledge. Methods A systematic chart review was conducted for patients visiting the Shimada Ryoiku medical Center for Challenged Children in Japan at the age of 15 years from January to December 2013. The primary outcome measure was the cancellation rate, defined as the number of missed visits divided by the number of scheduled visits. The cancellation rates during 24 months after the first visit were compared between outpatients with AD/HD and other psychiatric disorders, including pervasive developmental disorders (PDD), and developmental coordination disorders and/or communication disorders (DCD-CD). A generalized linear model with binomial distribution was used to examine factors associated with cancellation rates exclusively in the AD/HD group. Results We included 589 patients (mean ± SD age, 5.6 ± 3.4 years; 432 males) in the analysis. The cancellation rate in patients with AD/HD was 12.3% (95% confidence interval [CI]: 10.0–15.1), which was significantly higher than in those with PDD (5.6%, 95% CI: 3.8–8.3) and DCD-CD (5.3%, 95% CI: 3.6–7.8). Prescriptions of osmotic-release oral system-methylphenidate (OROS-MPH) and antipsychotics were associated with fewer cancellations in AD/HD patients (odds ratios: 0.61, 95% CI: 0.39–0.95 and 0.49, 95% CI: 0.25–0.95, respectively), although these significances did not find in the subgroup analysis including only patients with 6 years old. Conclusions Patients with AD/HD were more likely to miss appointments compared to those with other psychiatric disorders. The impact of AD/HD medications as well as potential psychiatric symptoms of their parents or caregivers on appointment cancellations needs to be evaluated in more detail in future investigations.

Objective: While antipsychotics are necessary for relapse prevention in the treatment of schizophrenia in general, some minority of patients may be maintained without continuous antipsychotic treatment. However, the characteristics of such patients are not well known and previous reports have not evaluated key elements such as physical comorbidities and functioning. Methods: Among 635 patients with schizophrenia who participated in a 12-year follow-up, those who were maintained without antipsychotic treatment for at least one year after the study were investigated. The patients underwent comprehensive assessments, including Positive and Negative Syndrome Scale (PANSS) for psychopathology, Cumulative Illness Rating Scale for Geriatrics (CIRS-G) for physical comorbidities, and Functional Assessment for Comprehensive Treatment of Schizophrenia (FACT-Sz), Barthel Index, and EuroQoL five dimensions (EQ5D) for function. Results: Six patients were included (mean ± standard deviation age, 66.8 ± 17.4 years; 4 inpatients). The four inpatients were old (77.8 ± 4.8 years) and chronically ill (duration of illness, 49.3 ± 12.5 years) with a high PANSS score (total score, 118.0 ± 9.8; negative syndrome subscale, 41.3 ± 6.9), low functioning (FACT-Sz, 9.8 ± 3.6; Barthel Index, 8.8 ± 9.6), and serious physical comorbidities (CIRS-G, 15.5 ± 1.1). By contrast, the two outpatients were relatively young (45.0 ± 12.0 years) and clinically in good condition (PANSS total score, 44.5 ± 0.5; Barthel Index, 100 for both; EQ5D, 0.85 ± 0.04). Conclusion: Although the number is limited, two types of patients with schizophrenia were identified who were free from ongoing antipsychotic treatment; 1) older chronic inpatients with serious physical comorbidities, and 2) younger outpatients with milder impairments. Future explorations are needed to identify those who will be successfully withdrawn from continuous antipsychotic treatment.

Objective: Non-convulsive status epilepticus (NCSE) can manifest as catatonia, although it is unclear how frequently such cases have been reported. The common clinical features of these two conditions are also unclear. Methods: Using the MEDLINE and Embase databases, we performed a systematic literature search to identify cases diagnosed with both catatonia, according to the Bush-Francis Catatonia Rating Scale, and NCSE, according to the Salzburg Consensus Criteria (last search: March 29, 2021). We extracted data on demographics, clinical features of catatonia, EEG findings, and treatments. Results: A total of 66 patients with catatonic NSCE (men, 49%; mean age, 42.0 years) were identified from our search. Of the 66 cases described: 30 (46%) showed motor symptoms; 35 (38%) occurred in patients with preceding episodes of epileptic seizures; 19 (29%) showed subtle ictal clinical phenomena, such as minor twitching of the mouth, periorbital region, and extremities; 22 (33%) presented with psychiatric symptoms prior to the onset of catatonia; 17 (26%) had a history of psychiatric diseases; and in 10 cases (15%), NSCE was confirmed by intentional or non-intentional long-term EEG monitoring. Benzodiazepines were used as the initial treatment for NCSE in 30 cases (49%), of which 20 cases (73%) improved with monotherapy. Discussion: A substantial number of cases included in the present review involved catatonia without any symptoms indicative of epilepsy, suggesting that NCSE may be misdiagnosed as a psychiatric disease, and highlighting the importance of the accurate diagnosis and treatment of NCSE in patients presenting with catatonia.

Introduction Clozapine is the gold standard of treatment for patients with treatment-resistant schizophrenia. However, approximately 60% of those patients do not respond to clozapine; moreover, clinical outcomes after clozapine discontinuation are unclear so far. Therefore, we conducted a systematic review to clarify the outcomes after clozapine discontinuation. Methods A systematic literature search was conducted, using MEDLINE and Embase with the following keywords: (clozapine AND (cessation∗ OR cease∗ OR withdraw∗ OR discontinu∗ OR halt∗ OR stop∗ OR switch*) AND (schizophreni∗ OR schizoaffective)). Results A total of 28 clinical studies from 27 articles were identified and included in this systematic review. Three randomized controlled trials reported worsening of psychiatric symptoms. In 10 single-Arm studies, the results of worsening and improving psychiatric symptoms were inconsistent. In one large retrospective cohort study, clozapine rechallenge, olanzapine, and antipsychotic polypharmacy had lower rehospitalization rates compared to no medication after clozapine discontinuation. In the other 14 retrospective studies, the vast majority showed worsening of clinical status after clozapine discontinuation. Among five studies on clinical outcomes after clozapine rechallenge, four reported improvements in clinical status in more than half of patients who rechallenged clozapine. The remaining study reported that the clozapine discontinuation-rechallenge group had a worse remission assessment score than the clozapine discontinuation-no rechallenge group. Discussion Clinical outcomes generally worsen after clozapine discontinuation. Clozapine rechallenge and olanzapine may be considered following clozapine discontinuation. The outcomes after clozapine discontinuation in clozapine non-responders remain inconclusive; therefore, well-designed studies are warranted.

Objective Clozapine is generally recommended to be prescribed in a divided dosing regimen based on its relatively short plasma half-life. However, there has been little evidence to support the superiority of divided dosing of clozapine over once-daily dosing. To our knowledge, there have been no studies examining differences in actual plasma concentrations or adverse effects between the 2 dosing strategies of clozapine. We aimed to compare actual plasma concentrations of clozapine between once-daily and divided dosing regimens, and to examine the relationships of these regimens with psychiatric symptoms and adverse effects of clozapine. Methods We analyzed data from 108 participants of a previous study conducted in 2 hospitals in Japan. A population pharmacokinetic model was used to estimate the peak and trough plasma concentrations of clozapine based on actual plasma concentrations. We evaluated psychiatric symptoms with the Brief Evaluation of Psychosis Symptom Domains and adverse effects of clozapine with the Glasgow Antipsychotic Side-effects Scale for Clozapine. Results The estimated peak and trough plasma concentrations of clozapine did not differ significantly between once-daily and divided dosing regimens. There were no significant differences in psychiatric symptoms except for depression/anxiety or subjective adverse effects of clozapine between the 2 dosing strategies. Conclusions Our findings tentatively support the feasibility and clinical utility of once-daily dosing of clozapine in clinical practice. Further studies are needed to replicate these findings and determine causality between dosing strategies and clinical outcomes.

Objective: While the most common cause of sudden cardiac arrest (SCA) in the general population is ischemic cardiac disease including acute myocardial infarction (AMI), previous preliminary data highlighted pulmonary embolism (PE) as a common cause of SCA among psychiatric patients. The aim of this study was to examine the proportion of patients with comorbid psychiatric disorders among patients hospitalized for either AMI or PE using a Japanese nationwide database. Methods: This study used Diagnosis Procedure Combination (DPC) data between April 2013 and March 2018 provided by the Ministry of Health, Labor, and Welfare. The DPC data included information on the causes of hospitalization and comorbidities of psychiatric diseases among inpatients in all acute care hospitals in Japan. The proportions of patients with schizophrenia (ICD-10 code F20), mood disorders (F31 or F32), and no psychiatric disorders were analyzed among patients who were hospitalized for AMI and PE. Results: The data from 351,159 AMI patients (mean age = 70.3 years) and 52,036 PE patients (mean age = 69.2 years) were used. Mortality rates were 8.0%–14.4% in AMI patients and 4.3%–9.8% in PE patients. The AMI group was predominantly male. The proportions of patients with schizophrenia and mood disorder were significantly higher in the PE group than in the AMI group (schizophrenia: 2.53% [1,314/52,036] vs 0.55% [1,922/351,159], P< .001; mood disorder: 2.94% [1,532/52,036] vs 0.60% [2,099/351,159], P< .001). Conclusions: The results highlight the importance of PE as a major cause of SCA in this specific population and the need for preventive measures to mitigate the mortality gap among patients with psychiatric disorders.