Chieh-Hsin Lin

Clinical symptoms, mainly negative symptoms, mediate the influence of neurocognition and social cognition on functional outcome of schizophrenia

BACKGROUND The functional outcome of schizophrenia is affected by multiple factors such as cognitive function and clinical symptoms. The complex relationship among cognitive function (both neuro- and social-cognitions), clinical symptoms, and functional outcome remains unclear. The current study employed structural equation modeling (SEM) to examine whether clinical symptoms mediate the relationship between cognitive function and functional outcome in a large cohort of patients with schizophrenia. METHOD Three hundred and two Han-Chinese patients with chronically stable schizophrenia received evaluation of cognitive function (using the Measurement and Treatment Research to Improve Cognition in Schizophrenia [MATRICS] Consensus Cognitive Battery, including 7 domains covering neurocognition and social cognition), clinical symptoms (including positive, negative and depressive symptoms), and functional outcome as assessed by Global Assessment of Functioning Scale and Quality of Life Scale. RESULTS SEM identified clinical symptoms as a mediator between cognitive function (including all 7 domains of MATRICS) and functional outcome in schizophrenia. The relationship between cognitive function and functional outcome was significant in the basic model. In the mediation model, the link between cognitive function and functional outcome was mediated by clinical symptoms, mainly negative symptoms. CONCLUSION This study suggests that clinical symptoms, mainly negative symptoms, mediate the influence of neurocognition and social cognition on functional outcome of schizophrenia. Future studies should explore the impact on other functional outcomes in different ethnicities and various illness phases.

Glutamate signaling in the pathophysiology and therapy of schizophrenia

Glutamatergic neurotransmission, particularly through the N-methyl-d-aspartate (NMDA) receptor, has drawn attention for its role in the pathophysiology of schizophrenia. This paper reviews the neurodevelopmental origin and genetic susceptibility of schizophrenia relevant to NMDA neurotransmission, and discusses the relationship between NMDA hypofunction and different domains of symptom in schizophrenia as well as putative treatment modality for the disorder. A series of clinical trials and a meta-analysis which compared currently available NMDA-enhancing agents suggests that glycine, d-serine, and sarcosine are more efficacious than d-cycloserine in improving the overall psychopathology of schizophrenia without side effect or safety concern. In addition, enhancing glutamatergic neurotransmission via activating the AMPA receptor, metabotropic glutamate receptor or inhibition of d-amino acid oxidase (DAO) is also reviewed. More studies are needed to determine the NMDA vulnerability in schizophrenia and to confirm the long-term efficacy, functional outcome, and safety of these NMDA-enhancing agents in schizophrenic patients, particularly those with refractory negative and cognitive symptoms, or serious adverse effects while taking the existing antipsychotic agents.

Benzoate, a D-Amino Acid Oxidase Inhibitor, for the Treatment of Early-Phase Alzheimer Disease: A Randomized, Double-Blind, Placebo-Controlled Trial

BACKGROUND N-methyl-D-aspartate receptor (NMDAR)-mediated neurotransmission is vital for learning and memory. Hypofunction of NMDAR has been reported to play a role in the pathophysiology of Alzheimer disease (AD), particularly in the early phase. Enhancing NMDAR activation might be a novel treatment approach. One of the methods to enhance NMDAR activity is to raise the levels of NMDA coagonists by blocking their metabolism. This study examined the efficacy and safety of sodium benzoate, a D-amino acid oxidase inhibitor, for the treatment of amnestic mild cognitive impairment and mild AD. METHODS We conducted a randomized, double-blind, placebo-controlled trial in four major medical centers in Taiwan. Sixty patients with amnestic mild cognitive impairment or mild AD were treated with 250-750 mg/day of sodium benzoate or placebo for 24 weeks. Alzheimers Disease Assessment Scale-cognitive subscale (the primary outcome) and global function (assessed by Clinician Interview Based Impression of Change plus Caregiver Input) were measured every 8 weeks. Additional cognition composite was measured at baseline and endpoint. RESULTS Sodium benzoate produced a better improvement than placebo in Alzheimers Disease Assessment Scale-cognitive subscale (p = .0021, .0116, and .0031 at week 16, week 24, and endpoint, respectively), additional cognition composite (p = .007 at endpoint) and Clinician Interview Based Impression of Change plus Caregiver Input (p = .015, .016, and .012 at week 16, week 24, and endpoint, respectively). Sodium benzoate was well-tolerated without evident side-effects. CONCLUSIONS Sodium benzoate substantially improved cognitive and overall functions in patients with early-phase AD. The preliminary results show promise for D-amino acid oxidase inhibition as a novel approach for early dementing processes.

NMDA Neurotransmission Dysfunction in Behavioral and Psychological Symptoms of Alzheimer’s Disease

Dementia has become an all-important disease because the population is aging rapidly and the cost of health care associated with dementia is ever increasing. In addition to cognitive function impairment, associated behavioral and psychological symptoms of dementia (BPSD) worsen patient’s quality of life and increase caregiver’s burden. Alzheimer’s disease is the most common type of dementia and both behavioral disturbance and cognitive impairment of Alzheimer’s disease are thought to be associated with the N-methyl-D-aspartate (NMDA) dysfunction as increasing evidence of dysfunctional glutamatergic neurotransmission had been reported in behavioral changes and cognitive decline in Alzheimer’s disease. We review the literature regarding dementia (especially Alzheimer’s disease), BPSD and relevant findings on glutamatergic and NMDA neurotransmission, including the effects of memantine, a NMDA receptor antagonist, and NMDA-enhancing agents, such as D-serine and D-cycloserine. Literatures suggest that behavioral disturbance and cognitive impairment of Alzheimer’s disease may be associated with excitatory neurotoxic effects which result in impairment of neuronal plasticity and degenerative processes. Memantine shows benefits in improving cognition, function, agitation/aggression and delusion in Alzheimer’s disease. On the other hand, some NMDA modulators which enhance NMDA function through the co-agonist binding site can also improve cognitive function and psychotic symptoms. We propose that modulating NMDA neurotransmission is effective in treating behavioral and psychological symptoms of Alzheimer’s disease. Prospective study using NMDA enhancers in patients with Alzheimer’s disease and associated behavioral disturbance is needed to verify this hypothesis.

Time to rehospitalization in patients with major depression vs. those with schizophrenia or bipolar I disorder in a public psychiatric hospital.

Compared rehospitalization rates in patients with schizophrenia or bipolar I disorder to patients with major depressive disorder remains unclear. This study aimed to compare the time to rehospitalization of the three groups. Other clinical variables were also examined. Rehospitalization status was monitored for all admitted inpatients with schizophrenia (n=637), bipolar I disorder (n=197), or major depressive disorder (n=191), from January 1, 2006 to December 31, 2006. Time to rehospitalization within 1 year after discharge was measured using the Kaplan-Meier method. Risk factors associated with rehospitalization were examined using the Cox proportional hazards regression model. The three groups were comparable for comorbid alcohol abuse/dependence, family history of severe psychiatric illness, years of education, and number of previous hospitalizations. No significant differences were noted among the three groups for the time to rehospitalization or the time to discontinuation. Age onset and number of previous admission were associated with risks of rehospitalization. This study suggests that the major depressive disorder, schizophrenia, and bipolar I disorder have comparable influences on time to rehospitalization and discontinuation from treatment and that earlier onset of illness and more previous hospitalizations are associated with higher risks of rehospitalization. Further prospective research is warranted.

NMDA neurotransmission dysfunction in mild cognitive impairment and Alzheimer's disease.

The prevalence of Alzheimers disease (AD) in the elderly is growing rapidly worldwide, and the deteriorating clinical course of AD places a heavy burden on both the patients and their families. Early detection and intervention of mild cognitive impairment in the early phase of AD is vital for the purpose of improving the cognitive performance of patients and preventing the existing deficits from worsening. However, the main compounds currently used to treat early AD, acetylcholinesterase inhibitors (AChEIs), are unsatisfactory in efficacy and safety. Moreover, evidence indicates that AChEIs are ineffective in treating AD at extremely early stages, which implies that mechanisms other than those targeted by AChEIs underlie the pathogenesis of AD. Dysfunctional glutamatergic neurotransmission, particularly that mediated by the N-methyl-D-aspartate (NMDA) receptor, has been reported to play a role in the pathophysiology of AD. The NMDA receptor (NMDAR) regulates synaptic plasticity, memory, and cognition, and the attenuation of NMDAR-mediated neurotransmission can result in impaired neuroplasticity and cognitive deficits in the aging brain. Furthermore, NMDARs also interact with amyloid beta peptide/amyloid precursor protein and tau protein, whose production represents the main manifestations of AD. In this paper, we review the evidence supporting NMDA dysfunction in both animal models of AD and patients afflicted with AD, and we also review the literature that suggests that NMDA-enhancing agents such as glycine and D-cycloserine can improve cognitive functions. The benefits and limitations of NMDAR antagonists that can diminish the excitatory neurotoxicity triggered by glutamate are also addressed in relation to AD. We propose that enhancing glutamatergic neurotransmission by activating the NMDAR may be effective in treating the cognitive decline that occurs in AD. Prospective studies on AD in which NMDA-enhancing agents are used are required to verify this hypothesis and confirm the long-term efficacy and safety of the treatment agents.

Clozapine protects bone mineral density in female patients with schizophrenia

Decreased bone mineral density (BMD) is common in patients with schizophrenia; however, the pathogenesis is unclear. Different classes of antipsychotic agents may affect BMD. This study systemically examined the effects of clozapine vs. other antipsychotics, and several hormonal and metabolic factors that may contribute to BMD in female patients with schizophrenia, who are more vulnerable than males. Forty-eight women with schizophrenia, treated with long-term antipsychotics of the prototype prolactin-sparing (PS) antipsychotic agent clozapine vs. prolactin-raising (PR) antipsychotics were enrolled. They were matched for demographic and clinical characteristics. Various factors, including blood levels of prolactin and sex hormones, psychopathological symptoms, global assessment of functioning, physical activity, and menopausal status, were determined to explore their contribution to low BMD (LBMD), defined as a dual-energy X-ray absorptiometer (DEXA) T score <-1. Overall, women receiving clozapine have better bone density than women receiving PR antipsychotics. Compared to PR antipsychotics, PS clozapine therapy is a protective factor (odds ratio 28.2, 95% confidence interval 2.37-336.10, p=0.008) for LBMD. Predictors for higher bone density in the clozapine group included higher clozapine dose (p<0.001), younger age (p<0.001), and higher thyroid-stimulating hormone level (p<0.001); in the PR group, higher body mass index (p=0.003) and lower alkaline phosphatase level (p=0.007) were associated with LBMD. This study suggests that clozapine treatment is beneficial for BMD compared to PR antipsychotic treatment in women with chronic schizophrenia, and clozapines bone-density protecting effect is dose-related.

FACTORS AFFECTING TIME TO REHOSPITALIZATION IN HAN CHINESE PATIENTS WITH SCHIZOPHRENIC DISORDER IN TAIWAN

Schizophrenic disorder is a lifelong illness. Hospitalization is a major event for the patient and his/her family, often indicating that the clinical symptoms have reached an intolerable level. The purpose of this study was to investigate the risk factors affecting the time to rehospitalization. Rehospitalization status was monitored for all schizophrenic patients discharged from Kai‐Suan Psychiatric Hospital from January 1, 2002 to December 31, 2002. Patients were followed‐up regarding rehospitalization until December 31, 2003. The Kaplan‐Meier method was used to calculate the mean time to rehospitalization. Risk factors associated with rehospitalization were examined by Cox proportional hazards regression model. Three hundred and thirty‐six patients were recruited for this study. The mean time to rehospitalization was 239 ± 7 days, with a rehospitalization rate of 54.5%. The mean time to discontinuation was 329 ± 5 days. Age at onset (hazard ratio = 0.978, 95% CI = 0.959—0.998, p = 0.031) and the number of previous hospitalizations (hazard ratio = 1.108, 95% CI = 1.058—1.161, p < 0.001) were found to be risk factors of shorter time to rehospitalization within 1 year after discharge. Further research should be carried out to test risk factors in a prospective study, and to assess the cost‐effectiveness of interventions to prevent rehospitalization.

New Treatment Strategies of Depression: Based on Mechanisms Related to Neuroplasticity

Major depressive disorder is a severe and complex mental disorder. Impaired neurotransmission and disrupted signalling pathways may influence neuroplasticity, which is involved in the brain dysfunction in depression. Traditional neurobiological theories of depression, such as monoamine hypothesis, cannot fully explain the whole picture of depressive disorders. In this review, we discussed new treatment directions of depression, including modulation of glutamatergic system and noninvasive brain stimulation. Dysfunction of glutamatergic neurotransmission plays an important role in the pathophysiology of depression. Ketamine, an N-methyl-D-aspartate (NMDA) receptor antagonist, has rapid and lasting antidepressive effects in previous studies. In addition to ketamine, other glutamatergic modulators, such as sarcosine, also show potential antidepressant effect in animal models or clinical trials. Noninvasive brain stimulation is another new treatment strategy beyond pharmacotherapy. Growing evidence has demonstrated that superficial brain stimulations, such as transcranial magnetic stimulation, transcranial direct current stimulation, cranial electrotherapy stimulation, and magnetic seizure therapy, can improve depressive symptoms. The antidepressive effect of these brain stimulations may be through modulating neuroplasticity. In conclusion, drugs that modulate neurotransmission via NMDA receptor and noninvasive brain stimulation may provide new directions of treatment for depression. Furthermore, exploring the underlying mechanisms will help in developing novel therapies for depression in the future.

Sex-specific factors for bone density in patients with schizophrenia.

Patients with schizophrenia are susceptible to low bone mineral density (BMD). Many risk factors have been suggested. However, it remains uncertain whether the risk factors differ between men and women. In addition, the study of bone density in men is neglected more often than that in women. This study aims to examine specific risk factors of low BMD in different sexes. Men (n=80) and women (n=115) with schizophrenia, similar in demographic and clinical characteristics, were enrolled in three centers. Clinical and laboratory variables (including blood levels of prolactin, sex and thyroid hormones, cortisol, calcium, and alkaline phosphatase) were collected. BMD was measured using a dual-energy X-ray absorptiometer. Men had lower BMD than women. Predictors for BMD in men included hyperprolactinemia (B=−0.821, P=0.009), body weight (B=0.024, P=0.046), and Global Assessment of Functioning score (B=0.027, P=0.043); in women, BMD was associated with menopause (B=−1.070, P<0.001), body weight (B=0.027, P=0.003), and positive symptoms (B=0.094, P<0.001). In terms of the effect of psychotic symptoms, positive symptoms were related positively to BMD in women, but not in men. The findings suggest that sex-specific risk factors should be considered for an individualized intervention of bone loss in patients with schizophrenia. Physicians should pay particular attention to bone density in men with hyperprolactinemia and postmenopausal women. Further prospective studies in other populations are warranted to confirm these findings.