•We conducted the first meta-analysis on metabolite levels of kynurenine pathway in patients with depression.•Out of 899 initial records, 22 articles were identified.•Kynurenic acid and kynurenine ...levels are decreased in patients with depression.•Quinolinic acid levels are increased in unmedicated patients with depression.•Future research should examine relationships between treatment and kynurenine pathway.
Abnormalities of the kynurenine (KYN) pathway may be implicated in the pathophysiology of depression. However, the relationships between depression and each metabolite of the KYN pathway remain uncertain. Therefore, we conducted a meta-analysis about the levels of the metabolites of KYN pathway between patients with depression and controls. Out of 899 initial records, we identified 22 articles to form the empirical basis. Seventeen, 10, and 18 studies examined levels of kynurenic acid (KYNA), quinolinic acid (QUIN), and KYN, respectively. KYNA and KYN levels were lower in patients with depression in comparison to controls, while QUIN levels did not differ between the two groups. Antidepressant-free patients showed decreased KYNA levels and increased QUIN levels compared with controls. Male ratios of the samples were negatively associated with study SMDs for KYNA. In conclusion, this meta-analysis revealed that patients with depression had decreased level of KYNA and KYN, whereas antidepressant-free patients showed increased level of QUIN. Nevertheless, given the heterogeneity among their sample characteristics, further research is clearly needed.
Alterations in glutamatergic neurotransmission are implicated in the pathophysiology of depression, and the glutamatergic system represents a treatment target for depression. To summarize the nature ...of glutamatergic alterations in patients with depression, we conducted a meta-analysis of proton magnetic resonance (
H-MRS) spectroscopy studies examining levels of glutamate. We used the search terms: depress* AND (MRS OR "magnetic resonance spectroscopy"). The search was performed with MEDLINE, Embase, and PsycINFO. The inclusion criteria were
H-MRS studies comparing levels of glutamate + glutamine (Glx), glutamate, or glutamine between patients with depression and healthy controls. Standardized mean differences (SMD) were calculated to assess group differences in the levels of glutamatergic neurometabolites. Forty-nine studies met the eligibility criteria, which included 1180 patients and 1066 healthy controls. There were significant decreases in Glx within the medial frontal cortex (SMD = -0.38; 95% CI, -0.69 to -0.07) in patients with depression compared with controls. Subanalyses revealed that there was a significant decrease in Glx in the medial frontal cortex in medicated patients with depression (SMD = -0.50; 95% CI, -0.80 to -0.20), but not in unmedicated patients (SMD = -0.27; 95% CI, -0.76 to 0.21) compared with controls. Overall, decreased levels of glutamatergic metabolites in the medial frontal cortex are linked with the pathophysiology of depression. These findings are in line with the hypothesis that depression may be associated with abnormal glutamatergic neurotransmission.
•TMS combined with EMG permits the generation of key neurophysiological indices in the cortex.•AD patients had increased motor cortical excitability and decreased cholinergic and GABAergic functions ...compared with HC.•MCI patients had increased motor cortical excitability and decreased cholinergic function compared with HC.•TMS neurophysiology are useful measure to understand the pathophysiology of AD and MCI.
Transcranial magnetic stimulation (TMS) is a non-invasive neurophysiological tool that enables the investigation of cortical excitability in the human brain. Paired-pulse TMS paradigms include short- and long-interval intracortical inhibition (SICI/LICI), intracortical facilitation (ICF), and short-latency afferent inhibition (SAI), which can assess neurophysiological functions of GABAergic, glutamatergic, and cholinergic neural circuits, respectively. We conducted the first systematic review and meta-analysis to compare these TMS indices among patients with AD, mild cognitive impairment (MCI), and healthy controls (HC). Our meta-analyses indicated that RMT, SAI, SICI, and LICI were significantly lower in patients with AD, while ICF did not show a difference in patients with AD compared with HC. In patients with MCI, RMT and SAI were significantly lower than in HC. In conclusion, motor cortical excitability was increased, while cholinergic function was decreased in AD and MCI in comparison with HC and patients with AD had decreased GABAergic and glutamatergic functions compared with HC. Our results warrant further studies to differentiate AD, MCI, and HC, employing multimodal TMS neurophysiology.
Repetitive transcranial magnetic stimulation (rTMS) is an effective clinical intervention for various neuropsychiatric diseases. However, it is still unclear whether rTMS has an effect on cognitive ...functioning. In this review, we aimed to systematically evaluate the cognitive effects of rTMS in depression, schizophrenia, and Alzheimer's disease. We searched PubMed (1996–2018) under the set terms to review randomized controlled trials (RCT) to examine the effectiveness of rTMS administered to the dorsolateral prefrontal cortex (DLPFC) and evaluated cognitive functions in patients with depression, schizophrenia, and Alzheimer's disease. Two authors reviewed each article and came to consensus on the inclusion and exclusion criteria. All eligible studies were reviewed, duplicates were removed, and data were extracted individually. The search identified 579 articles, 31 of which met inclusion and exclusion criteria. Among them, 15 were conducted in patients with depression, 11 in patients with schizophrenia, and 5 in patients with Alzheimer's disease. Specifically, 6 studies demonstrated a significant improvement of executive function across these diseases. Further, no evidence for cognitive adverse effects was found in these included rTMS studies. Although the heterogeneity between studies in terms of cognitive measures applied, stimulation parameters, and participants limits the ability to generalize conclusions, this review demonstrated that prefrontal rTMS could exert pro-cognitive effects on executive function and attention in some patients with depression but inconsistent cognitive impacts in any of the examined domains especially in patients with schizophrenia and Alzheimer's disease. The results warrant further rTMS studies that include systematic assessment of cognition across various neuropsychiatric diseases.
•Prefrontal rTMS could exert partial pro-cognitive effects in depression.•rTMS has inconsistent cognitive impacts in schizophrenia and Alzheimer's disease.•rTMS studies with comprehensive cognitive assessment in these diseases are needed.
Approximately 30% of patients with schizophrenia do not respond to antipsychotics and are thus considered to have treatment-resistant schizophrenia (TRS). To date, only four studies have examined ...glutamatergic neurometabolite levels using proton magnetic resonance spectroscopy (
H-MRS) in patients with TRS, collectively suggesting that glutamatergic dysfunction may be implicated in the pathophysiology of TRS. Notably, the TRS patient population in these studies had mild-to-moderate illness severity, which is not entirely reflective of what is observed in clinical practice. In this present work, we compared glutamate + glutamine (Glx) levels in the dorsal anterior cingulate cortex (dACC) and caudate among patients with TRS, patients with non-TRS, and healthy controls (HCs), using 3T
H-MRS (PRESS, TE = 35 ms). TRS criteria were defined by severe positive symptoms (i.e., ≥5 on 2 Positive and Negative Syndrome Scale (PANSS)-positive symptom items or ≥4 on 3 PANSS-positive symptom items), despite standard antipsychotic treatment. A total of 95 participants were included (29 TRS patients PANSS = 111.2 ± 20.4, 33 non-TRS patients PANSS = 49.8 ± 13.7, and 33 HCs). dACC Glx levels were higher in the TRS group vs. HCs (group effect: F2,75 = 4.74, p = 0.011; TRS vs. HCs: p = 0.012). No group differences were identified in the caudate. There were no associations between Glx levels and clinical severity in either patient group. Our results are suggestive of greater heterogeneity in TRS relative to non-TRS with respect to dACC Glx levels, necessitating further research to determine biological subtypes of TRS.
Accumulating evidence indicates that pathophysiology of schizophrenia involves abnormalities in the dopamine and glutamatergic neuronal systems. Antipsychotic medications are currently used to ...normalize dopaminergic function for schizophrenia. However, approximately 30 % of the patients have no response to antipsychotic medications, which is classified as treatment-resistant schizophrenia (TRS). Furthermore, dopamine and glutamate levels in the neural basis have been reported to differ between TRS and non-TRS. In this study, we assumed that these differences may affect music rhythm perception and production abilities between the two groups. We examined fifty-seven schizophrenia (26 TRS, 31 non-TRS) and thirty-one healthy controls (HCs) by using the Harvard Beat Assessment Test (H-BAT). As a result, we found that rhythm production was worse in patients with TRS compared to patients with non-TRS and HCs, while no difference was observed between patients with non-TRS and HCs. In addition, rhythm perception and production abilities were impaired in the whole patient group compared with HCs. Furthermore, in the patient group, the deficits were correlated with cognitive impairments. Collectively, these results suggest that patients with schizophrenia may have rhythm processing deficits, with particular a rhythm production problem in the TRS group.
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.
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.
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.
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.
Background:
Glutathione is among the important antioxidants to prevent oxidative stress. However, the relationships between abnormality in the glutathione system and pathophysiology of schizophrenia ...remain uncertain due to inconsistent findings on glutathione levels and/or glutathione-related enzyme activities in patients with schizophrenia.
Methods:
A systematic literature search was conducted using Embase, Medline, PsycINFO, and PubMed. Original studies, in which three metabolite levels (glutathione, glutathione disulfide, and total glutathione (glutathione+glutathione disulfide)) and five enzyme activities (glutathione peroxidase, glutathione reductase, glutamate-cysteine ligase, glutathione synthetase, and glutathione S-transferase) were measured with any techniques in both patients with schizophrenia and healthy controls, were included. Standardized mean differences were calculated to determine the group differences in the glutathione levels with a random-effects model.
Results:
We identified 41, 9, 15, 38, and seven studies which examined glutathione, glutathione disulfide, total glutathione, glutathione peroxidase, and glutathione reductase, respectively. Patients with schizophrenia had lower levels of both glutathione and total glutathione and decreased activity of glutathione peroxidase compared to controls. Glutathione levels were lower in unmedicated patients with schizophrenia than those in controls while glutathione levels did not differ between patients with first-episode psychosis and controls.
Conclusions:
Our findings suggested that there may be glutathione deficits and abnormalities in the glutathione redox cycle in patients with schizophrenia. However, given the small number of studies examined the entire glutathione system, further studies are needed to elucidate a better understanding of disrupted glutathione function in schizophrenia, which may pave the way for the development of novel therapeutic strategies in this disorder.
Depression is one of the common psychiatric disorders in old age. Major depressive disorder (MDD) has been identified as a risk factor or prodrome for neurodegenerative dementias, suggesting ...neuropathological overlaps and a continuum between MDD and neurodegenerative disorders. In this study, we examined tau and amyloid-β (Aβ) accumulations in the brains of MDD and healthy controls using positron emission tomography (PET) to explore pathological substrates of this illness. Twenty MDD and twenty age-matched, healthy controls were examined by PET with a tau radioligand,
CPBB3, and an Aβ radioligand,
CPiB. Radioligand retentions were quantified as a standardized uptake value ratio (SUVR). We also assessed clinical manifestations of the patients using the 17-item Hamilton Depression Scale, the Geriatric Depression Scale, and psychotic symptoms. Mean cortical
CPBB3 SUVRs in MDD patients were significantly higher than those of healthy controls. These values were higher in MDD patients with psychotic symptoms than in those without any. The present findings indicate that tau depositions may underlie MDD, and especially in patients with psychotic symptoms. PET detection of tau accumulations may provide mechanistic insights into neuronal dysfunctions in these cases and could serve as predictions of their clinical consequences.
Delay discounting (DD) represents decreased subjective value for delayed reward relative to the same reward at present. The concept of DD has been applied for pathophysiology of addiction and ...psychiatric disorders. However, the detailed neuroimaging correlates of DD underlying pathophysiology still remain unclear. Thus, we conducted a systematic review to investigate neural correlates of DD on magnetic resonance imaging studies among addiction and psychiatric disorders. Specific search terms were set on PubMed to identify relevant articles. Initial search identified 551 records and 31 studies met the inclusion criteria. The present review revealed that greater DD was correlated with increased activity in areas related to reward evaluation and prediction as well as decreased activity in areas related to cognitive control. Healthy controls showed smaller changes in activities of these areas associated with DD when compared to patient groups. As the neural basis related to DD, three neural networks have been proposed that are associated with the actions of short-term interests and long-term benefits. Among the three potential neural networks on DD, the first one included the ventromedial prefrontal cortex and ventral striatum and implicated in evaluating reward values, the second network included the anterior cingulate cortex and linked to cognitive control, and the third network included the middle temporal gyrus and was involved in predictions and affection. This review generated consistent findings on the neural basis of DD among patients with addiction and psychiatric disorders, which may represent the pathophysiology related to DD and impulsivity of mental illness.
•In general, patients with addiction and psychiatric disorders have greater DD.•Greater DD correlates with increased activity in the reward evaluation system.•Greater DD is associated with decreased activity in the cognitive control.
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