D2 receptor blockade by risperidone correlates with attention deficits in late-life schizophrenia

The Effect of Antipsychotics on Cognition in Schizophrenia-A Current Narrative Review

The majority of schizophrenia-affected individuals display deficiencies in multiple cognitive domains such as attention, working memory, long-term memory, and learning, deficiencies that are stable throughout the disease. The purpose of this narrative review was to examine the effect of antipsychotics on several cognitive domains affected by schizophrenia. Methods: We searched MEDLINE, Elsevier, Scopus, and DOAJ databases for randomized controlled trials and other studies investigating the effects of typical and atypical antipsychotics on cognition in patients with schizophrenia in studies conducted in the last decade. Results: The majority of studies included in this review showed that antipsychotics (especially SGAs) have positive effects on both cognition and general psychopathology of schizophrenia. We mention that treatment with antipsychotic substances represents an ongoing effort of the researchers, who are constantly searching for the best approach to meet the mental health needs of schizophrenia patients. Conclusions: Even with those positive results, it should be noted that more studies are needed in order to fully observe the various effects of certain antipsychotic substances on cognition.

Antipsychotic polypharmacy reduction versus polypharmacy continuation for people with schizophrenia

BACKGROUND

In clinical practice, different antipsychotics can be combined in the treatment of people with schizophrenia (polypharmacy). This strategy can aim at increasing efficacy, but might also increase the adverse effects due to drug-drug interactions. Reducing polypharmacy by withdrawing one or more antipsychotics may reduce this problem, but must be done carefully, in order to maintain efficacy.

OBJECTIVES

To examine the effects and safety of reducing antipsychotic polypharmacy compared to maintaining people with schizophrenia on the same number of antipsychotics.

SEARCH METHODS

On 10 February 2021, we searched the Cochrane Schizophrenia Group's Study-Based Register of Trials, which is based on CENTRAL, CINAHL, ClinicalTrials.Gov, Embase, ISRCTN, MEDLINE, PsycINFO, PubMed and WHO ICTRP.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) that compared reduction in the number of antipsychotics to continuation of the current number of antipsychotics. We included adults with schizophrenia or related disorders who were receiving more than one antipsychotic and were stabilised on their current treatment.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened all the identified references for inclusion, and all the full papers. We contacted study authors if we needed any further information. Two review authors independently extracted the data, assessed the risk of bias using RoB 2 and the certainty of the evidence using the GRADE approach. The primary outcomes were: quality of life assessed as number of participants with clinically important change in quality of life; service use assessed as number of participants readmitted to hospital and adverse effects assessed with number of participants leaving the study early due to adverse effects.

MAIN RESULTS

We included five RCTs with 319 participants. Study duration ranged from three months to one year. All studies compared polypharmacy continuation with two antipsychotics to polypharmacy reduction to one antipsychotic.  We assessed the risk of bias of results as being of some concern or at high risk of bias. A lower number of participants left the study early due to any reason in the polypharmacy continuation group (risk ratio (RR) 0.44, 95% confidence interval (CI) 0.29 to 0.68; I2 = 0%; 5 RCTs, n = 319; low-certainty evidence), and a lower number of participants left the study early due to inefficacy (RR 0.21, 95% CI 0.07 to 0.65; I2 = 0%; 3 RCTs, n = 201).  Polypharmacy continuation resulted in more severe negative symptoms (MD 3.30, 95% CI 1.51 to 5.09; 1 RCT, n = 35). There was no clear difference between polypharmacy reduction and polypharmacy continuation on readmission to hospital, leaving the study early due to adverse effects, functioning, global state, general mental state and positive symptoms, number of participants with at least one adverse effect, weight gain and other specific adverse effects, mortality and cognition. We assessed the certainty of the evidence as very low or low across measured outcomes. No studies reported quality of life, days in hospital, relapse, depressive symptoms, behaviour and satisfaction with care. Due to lack of data, it was not possible to perform some planned sensitivity analyses, including one controlling for increasing the dose of the remaining antipsychotic. As a result, we do not know if the observed results might be influenced by adjustment of dose of remaining antipsychotic compound.

AUTHORS' CONCLUSIONS

This review summarises the latest evidence on polypharmacy continuation compared with polypharmacy reduction. Our results show that polypharmacy continuation might be associated with a lower number of participants leaving the study early, especially due to  inefficacy. However, the evidence is of low and very low certainty and the data analyses based on few study only, so that it is not possible to draw strong conclusions based on the results of the present review. Further high-quality RCTs are needed to investigate this important topic.

Both unmedicated and medicated individuals with schizophrenia show impairments across a wide array of cognitive and reinforcement learning tasks

BACKGROUND

Schizophrenia is a disorder characterized by pervasive deficits in cognitive functioning. However, few well-powered studies have examined the degree to which cognitive performance is impaired even among individuals with schizophrenia not currently on antipsychotic medications using a wide range of cognitive and reinforcement learning measures derived from cognitive neuroscience. Such research is particularly needed in the domain of reinforcement learning, given the central role of dopamine in reinforcement learning, and the potential impact of antipsychotic medications on dopamine function.

METHODS

The present study sought to fill this gap by examining healthy controls (N = 75), unmedicated (N = 48) and medicated (N = 148) individuals with schizophrenia. Participants were recruited across five sites as part of the CNTRaCS Consortium to complete tasks assessing processing speed, cognitive control, working memory, verbal learning, relational encoding and retrieval, visual integration and reinforcement learning.

RESULTS

Individuals with schizophrenia who were not taking antipsychotic medications, as well as those taking antipsychotic medications, showed pervasive deficits across cognitive domains including reinforcement learning, processing speed, cognitive control, working memory, verbal learning and relational encoding and retrieval. Further, we found that chlorpromazine equivalency rates were significantly related to processing speed and working memory, while there were no significant relationships between anticholinergic load and performance on other tasks.

CONCLUSIONS

These findings add to a body of literature suggesting that cognitive deficits are an enduring aspect of schizophrenia, present in those off antipsychotic medications as well as those taking antipsychotic medications.

Relationships Among History of Psychosis, Cognition and Functioning in Later-Life Remitted Major Depression

OBJECTIVE

This study tested the hypotheses that, in older adults with remitted major depression, a history of psychotic features and poorer neuropsychological performance would be independently associated with poorer everyday functioning, but that neuropsychological performance would explain more of the variance in functioning than history of psychotic features.

METHODS

This cross-sectional study included 73 patients aged 50 years or older with remitted psychotic major depression or nonpsychotic major depression. The dependent variables were subjective and objective measures of function. The independent variables were history of psychotic features during one or more major depressive episodes in the previous 10 years and neuropsychological performance. Linear regression models examined the association of independent variables with function, controlling for pertinent covariates. Effect sizes were calculated for the magnitude of difference in function between the patient participants and an age- and gender-matched nonpsychiatric group, and distribution of functioning scores were compared between groups.

RESULTS

In separate models, history of psychotic features and poorer processing speed, executive function, and verbal learning were independently associated with poorer participant-reported functioning and performance-based functioning. However, the association of psychotic features with functioning was no longer statistically significant when tested in the same models as neuropsychological measures. Effect sizes of the difference in functioning between patients and the nonpsychiatric group were significantly larger for the remitted psychotic than the remitted nonpsychotic depression group; functioning scores were more heterogeneous in the remitted psychotic depression group.

CONCLUSION

Patients with remitted psychotic depression exhibit greater, and clinically important, impairment in everyday functioning than those with remitted nonpsychotic depression. Neuropsychological impairment appears to contribute to this relationship.

Subcortical Dopamine and Cognition in Schizophrenia: Looking Beyond Psychosis in Preclinical Models

Schizophrenia is characterized by positive, negative and cognitive symptoms. All current antipsychotic treatments feature dopamine-receptor antagonism that is relatively effective at addressing the psychotic (positive) symptoms of schizophrenia. However, there is no clear evidence that these medications improve the negative or cognitive symptoms, which are the greatest predictors of functional outcomes. One of the most robust pathophysiological observations in patients with schizophrenia is increased subcortical dopamine neurotransmission, primarily in the associative striatum. This brain area has an important role in a range of cognitive processes. Dopamine is also known to play a major part in regulating a number of cognitive functions impaired in schizophrenia but much of this research has been focused on cortical dopamine. Emerging research highlights the strong influence subcortical dopamine has on a range of cognitive domains, including attention, reward learning, goal-directed action and decision-making. Nonetheless, the precise role of the associative striatum in the cognitive impairments observed in schizophrenia remains poorly understood, presenting an opportunity to revisit its contribution to schizophrenia. Without a better understanding of the mechanisms underlying cognitive dysfunction, treatment development remains at a standstill. For this reason, improved preclinical animal models are needed if we are to understand the complex relationship between subcortical dopamine and cognition. A range of new techniques are facillitating the discrete manipulation of dopaminergic neurotransmission and measurements of cognitive performance, which can be investigated using a variety of sensitive translatable tasks. This has the potential to aid the successful incorporation of recent clinical research to address the lack of treatment strategies for cognitive symptoms in schizophrenia. This review will give an overview on the current state of research focused on subcortical dopamine and cognition in the context of schizophrenia research. We also discuss future strategies and approaches aimed at improving the translational outcomes for the treatment of cognitive deficits in schizophrenia.

Relationship of common variants in CHRNA5 with early-onset schizophrenia and executive function

Altered cholinergic neural transmission is hypothesized to increase susceptibility to cognitive deficits in psychotic disorders such as schizophrenia (SCZ). The nicotinic acetylcholine receptor α5 subunit gene (CHRNA5) is reported to be associated with cognitive function in nicotine-dependent populations and SCZ in non-smoking SCZ patients. Nevertheless, it is still not clear whether the CHRNA5 gene contributes to susceptibility to the cognitive deficits of SCZ without smoking. To further clarify the role of CHRNA5, we designed a two-stage, case-control study to examine the association between CHRNA5 and SCZ and its clinical features adjusted for smoking status in early-onset SCZ patients. A total of 15 tag single nucleotide polymorphisms (SNPs) on CHRNA5 were genotyped in the discovery stage, which included 485 early-onset SCZ patients and 1018 controls, and then, we replicated this association in a confirmatory population of 674 patients and 1886 controls. The rs16969968 SNP was identified as significantly associated with SCZ in both datasets. In addition, the severity of psychotic symptoms and cognitive deficits was assessed using the Positive and Negative Syndrome Scale (PANSS) and the Wisconsin Card Sorting Test (WCST). The rs16969968 SNP was associated with psychotic symptoms in patients and with cognitive function in patients and controls. Our results show that rs16969968 on CHRNA5 is tightly linked to genetic susceptibility, psychotic symptoms and cognitive deficits in SCZ in an early-onset Chinese population, suggesting that CHRNA5 may play an important role in the etiology of SCZ.

The effects of illness severity, cognition, and estimated antipsychotic dopamine receptor occupancy on insight into the illness in schizophrenia: An analysis of clinical antipsychotic trials of intervention effectiveness (CATIE) data

BACKGROUND

The relationship between dopamine D₂ receptor (D₂R) occupancy and impaired illness awareness (IIA) remains unclear. While IIA is associated with illness severity and cognitive dysfunction, antipsychotic medication, the principal treatment for schizophrenia, indirectly improves IIA, but may simultaneously contribute to cognitive dysfunction at supratherapeutic doses.

AIM AND METHODS

We investigated the influence of estimated D₂R (Est.D₂R) occupancy by antipsychotics on the relationships between IIA and illness severity, and IIA and cognition. IIA was assessed in 373 adult patients with schizophrenia (18-62 years) using data from CATIE. IIA was measured using the Positive and Negative Syndrome Scale (PANSS) item G12. D₂R occupancy levels were estimated from plasma concentrations for risperidone, olanzapine, and ziprasidone. Correlation, regression, and path analyses were performed to examine IIA's relationship to illness severity, cognition, and Est.D₂R.

RESULTS

Illness severity was predictive of IIA. However, premorbid IQ, cognition, and Est.D₂R did not predict IIA, and Est.D₂R did not serve either a moderating or mediating role in both regression and path analyses.

CONCLUSIONS

Consistent with previous literature, our results suggest that IIA is a function of illness severity in adult patients with schizophrenia. Future studies should explore whether D₂R occupancy mediates the relationships between IIA and illness severity, and IIA and cognitive dysfunction, in late-life schizophrenia (i.e. ≥60 years) given the effects of aging on cognition, IIA, and antipsychotic sensitivity.

Dopamine modulates the reward experiences elicited by music

Understanding how the brain translates a structured sequence of sounds, such as music, into a pleasant and rewarding experience is a fascinating question which may be crucial to better understand the processing of abstract rewards in humans. Previous neuroimaging findings point to a challenging role of the dopaminergic system in music-evoked pleasure. However, there is a lack of direct evidence showing that dopamine function is causally related to the pleasure we experience from music. We addressed this problem through a double blind within-subject pharmacological design in which we directly manipulated dopaminergic synaptic availability while healthy participants (n = 27) were engaged in music listening. We orally administrated to each participant a dopamine precursor (levodopa), a dopamine antagonist (risperidone), and a placebo (lactose) in three different sessions. We demonstrate that levodopa and risperidone led to opposite effects in measures of musical pleasure and motivation: while the dopamine precursor levodopa, compared with placebo, increased the hedonic experience and music-related motivational responses, risperidone led to a reduction of both. This study shows a causal role of dopamine in musical pleasure and indicates that dopaminergic transmission might play different or additive roles than the ones postulated in affective processing so far, particularly in abstract cognitive activities.

Dopamine and Working Memory: Genetic Variation, Stress and Implications for Mental Health

At the molecular level, the neurotransmitter dopamine (DA) is a key regulatory component of executive function in the prefrontal cortex (PFC) and dysfunction in dopaminergic (DAergic) circuitry has been shown to result in impaired working memory (WM). Research has identified multiple common genetic variants suggested to impact on the DA system functionally and also behaviourally to alter WM task performance. In addition, environmental stressors impact on DAergic tone, and this may be one mechanism by which stressors confer vulnerability to the development of neuropsychiatric conditions. This chapter aims to evaluate the impact of key DAergic gene variants suggested to impact on both synaptic DA levels (COMT, DAT1, DBH, MAOA) and DA receptor function (ANKK1, DRD2, DRD4) in terms of their influence on visuospatial WM. The role of stressors and interaction with the genetic background is discussed in addition to discussion around some of the implications for precision psychiatry. This and future work in this area aim to disentangle the neural mechanisms underlying susceptibility to stress and their impact and relationship with cognitive processes known to influence mental health vulnerability.

Intrinsically regulated learning is modulated by synaptic dopamine signaling

We recently provided evidence that an intrinsic reward-related signal-triggered by successful learning in absence of any external feedback-modulated the entrance of new information into long-term memory via the activation of the dopaminergic midbrain, hippocampus, and ventral striatum (the SN/VTA-Hippocampal loop; Ripollés et al., 2016). Here, we used a double-blind, within-subject randomized pharmacological intervention to test whether this learning process is indeed dopamine-dependent. A group of healthy individuals completed three behavioral sessions of a language-learning task after the intake of different pharmacological treatments: a dopaminergic precursor, a dopamine receptor antagonist or a placebo. Results show that the pharmacological intervention modulated behavioral measures of both learning and pleasantness, inducing memory benefits after 24 hr only for those participants with a high sensitivity to reward. These results provide causal evidence for a dopamine-dependent mechanism instrumental in intrinsically regulated learning and further suggest that subject-specific reward sensitivity drastically alters learning success.

Dose reduction of risperidone and olanzapine can improve cognitive function and negative symptoms in stable schizophrenic patients: A single-blinded, 52-week, randomized controlled study

BACKGROUND

The long-term effects of dose reduction of atypical antipsychotics on cognitive function and symptomatology in stable patients with schizophrenia remain unclear. We sought to determine the change in cognitive function and symptomatology after reducing risperidone or olanzapine dosage in stable schizophrenic patients.

METHODS

Seventy-five stabilized schizophrenic patients prescribed risperidone (≥4 mg/day) or olanzapine (≥10 mg/day) were randomly divided into a dose-reduction group ( n=37) and a maintenance group ( n=38). For the dose-reduction group, the dose of antipsychotics was reduced by 50%; for the maintenance group, the dose remained unchanged throughout the whole study. The Positive and Negative Syndrome Scale, Negative Symptom Assessment-16, Rating Scale for Extrapyramidal Side Effects, and Measurement and Treatment Research to Improve Cognition in Schizophrenia (MATRICS) Consensus Cognitive Battery were measured at baseline, 12, 28, and 52 weeks. Linear mixed models were performed to compare the Positive and Negative Syndrome Scale, Negative Symptom Assessment-16, Rating Scale for Extrapyramidal Side Effects and MATRICS Consensus Cognitive Battery scores between groups.

RESULTS

The linear mixed model showed significant time by group interactions on the Positive and Negative Syndrome Scale negative symptoms, Negative Symptom Assessment-16, Rating Scale for Extrapyramidal Side Effects, speed of processing, attention/vigilance, working memory and total score of MATRICS Consensus Cognitive Battery (all p<0.05). Post hoc analyses showed significant improvement in Positive and Negative Syndrome Scale negative subscale, Negative Symptom Assessment-16, Rating Scale for Extrapyramidal Side Effects, speed of processing, working memory and total score of MATRICS Consensus Cognitive Battery for the dose reduction group compared with those for the maintenance group (all p<0.05).

CONCLUSIONS

This study indicated that a risperidone or olanzapine dose reduction of 50% may not lead to more severe symptomatology but can improve speed of processing, working memory and negative symptoms in patients with stabilized schizophrenia.

The relationship between dopamine receptor blockade and cognitive performance in schizophrenia: a [11C]-raclopride PET study with aripiprazole

Aripiprazole's effects on cognitive function in patients with schizophrenia are unclear because of the difficulty in disentangling specific effects on cognitive function from secondary effects due to the improvement in other schizophrenic symptoms. One approach to address this is to use an intermediate biomarker to investigate the relationship between the drug's effect on the brain and change in cognitive function. This study aims to investigate aripiprazole's effect on working memory by determining the correlation between dopamine D2/3 (D2/3) receptor occupancy and working memory of patients with schizophrenia. Seven patients with schizophrenia participated in the study. Serial positron emission tomography (PET) scans with [¹¹C]raclopride were conducted at 2, 26, and 74 h after the administration of aripiprazole. The subjects performed the N-back task just after finishing the [¹¹C]raclopride PET scan. The mean (±SD) D2/3 receptor occupancies were 66.9 ± 6.7% at 2 h, 65.0 ± 8.6% at 26, and 57.7 ± 11.2% at 74 h after administering aripiprazole. Compared with performance on the zero-back condition, performance in memory-loaded conditions (one-, two-, and three-back conditions) was significantly related to D2/3 receptor occupancy by aripiprazole (error rate: ß = -2.236, t = -6.631, df = 53.947, and p = 0.001; reaction time: ß = -9.567, t = -2.808, df = 29.967, and p = 0.009). Although the sample size was relatively small, these results suggest that aripiprazole as a dopamine-partial agonist could improve cognitive function in patients with schizophrenia.

Serum levels of second-generation antipsychotics are associated with cognitive function in psychotic disorders

OBJECTIVES

Antipsychotics are effective in treating psychosis and mood episodes; however, the effect on cognition is less known. We investigated the association between serum levels of second-generation antipsychotics (SGAs) and cognitive performance in psychosis spectrum disorders in a naturalistic setting.

METHODS

A total of 495 patients with a DSM-IV Schizophrenia and Other Psychotic Disorders (SCZ, n = 373) or Bipolar Disorder (BD, n = 122) diagnosis treated with olanzapine, quetiapine, aripiprazole or risperidone were tested neuropsychologically with concurrent measurement of the serum concentration of the drug. Linear regression was used for association analyses.

RESULTS

Attention was positively associated with the olanzapine concentration (standardised beta (β) coefficient = 0.19, P = .006), and short-term verbal memory and verbal fluency were negatively associated with the quetiapine (β = -0.24, P = .004) and risperidone (β = -0.37, P = .007) concentrations respectively.

CONCLUSIONS

The present results suggest that SGA serum concentration is associated with better attention (small effect size), and worse verbal memory (small effect size) and verbal fluency (medium effect size). These findings are in line with the notion that SGAs affect aspects of cognitive function, and suggest careful dosing in patients with severe memory and executive problems.

The effect of COMT Val158Met and DRD2 C957T polymorphisms on executive function and the impact of early life stress

INTRODUCTION

Previous research has indicated that variation in genes encoding catechol-O-methyltransferase (COMT) and dopamine receptor D2 (DRD2) may influence cognitive function and that this may confer vulnerability to the development of mental health disorders such as schizophrenia. However, increasing evidence suggests environmental factors such as early life stress may interact with genetic variants in affecting these cognitive outcomes. This study investigated the effect of COMT Val158Met and DRD2 C957T polymorphisms on executive function and the impact of early life stress in healthy adults.

METHODS

One hundred and twenty-two healthy adult males (mean age 35.2 years, range 21-63) were enrolled in the study. Cognitive function was assessed using Cambridge Neuropsychological Test Automated Battery and early life stress was assessed using the Childhood Traumatic Events Scale (Pennebaker & Susman, 1988).

RESULTS

DRD2 C957T was significantly associated with executive function, with CC homozygotes having significantly reduced performance in spatial working memory and spatial planning. A significant genotype-trauma interaction was found in Rapid Visual Information Processing test, a measure of sustained attention, with CC carriers who had experienced early life stress exhibiting impaired performance compared to the CC carriers without early life stressful experiences. There were no significant findings for COMT Val158Met.

CONCLUSIONS

This study supports previous findings that DRD2 C957T significantly affects performance on executive function related tasks in healthy individuals and shows for the first time that some of these effects may be mediated through the impact of childhood traumatic events. Future work should aim to clarify further the effect of stress on neuronal systems that are known to be vulnerable in mental health disorders and more specifically what the impact of this might be on cognitive function.

Insight into illness and its relationship to illness severity, cognition and estimated antipsychotic dopamine receptor occupancy in schizophrenia: An antipsychotic dose reduction study

Little is known about the influence of D₂ receptor occupancy on impaired insight into illness (III)-a core feature of schizophrenia. III is associated with illness severity and cognitive dysfunction. Comparably, supratherapeutic D₂ receptor occupancy can impair cognition. However, it is unclear how illness severity, cognition, and D₂ receptor occupancy interact to influence III in schizophrenia. The aim of this study was to explore the influence of antipsychotic dose reduction on the relationships of illness severity and cognition to III. III was assessed at baseline and 28 weeks post-antipsychotic dose reduction in 16 participants with schizophrenia and plasma antipsychotic concentrations. III was assessed primarily with the Schedule for the Assessment of Insight-Japanese version, and secondarily with the Positive and Negative Syndrome Scale item G12. Correlation and regression analyses were performed to explore III's relationship to illness severity, cognition, and estimated D₂ receptor occupancy (Est.D₂). Cognition and Est.D₂ predicted III at baseline. At 28 weeks post-reduction, illness severity and Est.D₂ predicted III. Our findings suggest a complex relationship may exist among III, illness severity, cognition and Est.D₂. At higher D₂ receptor occupancies, III is influenced by cognitive dysfunction, whereas, at lower occupancies, illness severity has a stronger effect on III.

Preliminary evidence that negative symptom severity relates to multilocus genetic profile for dopamine signaling capacity and D2 receptor binding in healthy controls and in schizophrenia

Deficits in central, subcortical dopamine (DA) signaling may underlie negative symptom severity, particularly anhedonia, in healthy individuals and in schizophrenia. To investigate these relationships, we assessed negative symptoms with the Schedule for the Assessment of Negative Symptoms and the Brief Negative Symptom Scale (BNSS) and self-reported anhedonia with the Scales for Physical and Social Anhedonia (SPSA), Temporal Experience of Pleasure Scale, and Snaith-Hamilton Pleasure Scale in 36 healthy controls (HC), 27 siblings (SIB) of individuals with schizophrenia, and 66 individuals with schizophrenia or schizoaffective disorder (SCZ). A subset of participants (N = 124) were genotyped for DA-related polymorphisms in genes for DRD4, DRD2/ANKK1, DAT1, and COMT, which were used to construct biologically-informed multi-locus genetic profile (MGP) scores reflective of subcortical dopaminergic signaling. DA receptor type 2 (D2R) binding was assessed among a second subset of participants (N = 23) using PET scans with the D2R-selective, non-displaceable radioligand (N-[¹¹C]methyl)benperidol. Higher MGP scores, reflecting elevated subcortical dopaminergic signaling capacity, were associated with less negative symptom severity, as measured by the BNSS, across all participants. In addition, higher striatal D2R binding was associated with less physical and social anhedonia, as measured by the SPSA, across HC, SIB, and SCZ. The current preliminary findings support the hypothesis that subcortical DA function may contribute to negative symptom severity and self-reported anhedonia, independent of diagnostic status.

Cognition and Dopamine D2 Receptor Availability in the Striatum in Older Patients with Schizophrenia

OBJECTIVES

To assess the impact of reducing the dose of antipsychotics on cognition and dopaminergic D₂ receptor availability in the whole striatum, and identify their relationship in patients with schizophrenia aged 50 years or older.

DESIGN

Open-label prospective PET [¹¹C]-raclopride study.

SETTING

A tertiary care center outpatient setting.

PARTICIPANTS

Thirty-seven clinically stable participants with schizophrenia or schizoaffective disorder, aged 50 years or greater, and having been treated with olanzapine or risperidone monotherapy at the same dose for at least 6 months.

INTERVENTION

Gradual reduction in their olanzapine or risperidone daily dose of up to 40%.

MEASUREMENTS

Clinical and cognitive assessments, and [¹¹C]-raclopride PET to determine D₂ receptor availability at baseline and after the dose reduction. Main outcome measures were overall cognition and D₂ receptor availability in whole striatum.

RESULTS

Reducing the antipsychotic dose resulted in an increase in D₂ receptor availability in the whole striatum and an association between D₂ receptor availability and overall cognition despite lack of change in the latter. There was also an association between change in D₂ receptor availability and change in overall cognition.

CONCLUSIONS

Our findings suggest that optimizing D₂ receptor availability by reducing antipsychotic dose allows this system to contribute more significantly to cognitive function in patients with schizophrenia. This uncovered association could be harnessed by cognitive-enhancing interventions.

Cognitive function and risperidone long-acting injection vs. paliperidone palmitate in schizophrenia: a 6-month, open-label, randomized, pilot trial

BACKGROUND

Recently, long-acting injection (LAI) of second-generation antipsychotics has become a valuable strategy for the treatment of schizophrenia. However, few studies have compared the effects of different LAI antipsychotics on cognitive functions so far. The present study aimed to compare the influence of risperidone LAIs (RLAI) and paliperidone palmitate LAIs (PP) on cognitive function in outpatients with schizophrenia.

METHODS

In this 6-month, open-label, randomized, and controlled study, 30 patients with schizophrenia who were treated with RLAIs were randomly allocated to the RLAI-continued group or the PP group. At baseline and 6 months, the patients were evaluated using the Brief Assessment of Cognition in Schizophrenia (BACS) that was the primary outcome of the study. The Subjective Well-being under Neuroleptic drug treatment-Short form (SWNS), the Positive and Negative Syndrome Scale (PANSS), and the Drug-Induced Extrapyramidal Symptoms Scale (DIEPSS) scores were secondary outcome variables and they were tested at the same time points.

RESULTS

The two groups did not differ in terms of PANSS, DIEPSS, or SWNS total score changes. However, the BACS score for the attention and processing speed item showed higher improvement in the PP group than the RLAI group (p = 0.039).

CONCLUSIONS

The results of this preliminary study suggest that PPs may improve attention and processing speed more than RLAIs. Anyway, a replication in a larger and double-blind study is needed.

TRIAL REGISTRATION

UMIN000014470 . Registered 10 July 2014.

Assessing the synergy between cholinomimetics and memantine as augmentation therapy in cognitive impairment in schizophrenia. A virtual human patient trial using quantitative systems pharmacology

While many drug discovery research programs aim to develop highly selective clinical candidates, their clinical success is limited because of the complex non-linear interactions of human brain neuronal circuits. Therefore, a rational approach for identifying appropriate synergistic multipharmacology and validating optimal target combinations is desperately needed. A mechanism-based Quantitative Systems Pharmacology (QSP) computer-based modeling platform that combines biophysically realistic preclinical neurophysiology and neuropharmacology with clinical information is a possible solution. This paper reports the application of such a model for Cognitive Impairment In Schizophrenia (CIAS), where the cholinomimetics galantamine and donepezil are combined with memantine and with different antipsychotics and smoking in a virtual human patient experiment. The results suggest that cholinomimetics added to antipsychotics have a modest effect on cognition in CIAS in non-smoking patients with haloperidol and risperidone and to a lesser extent with olanzapine and aripiprazole. Smoking reduces the effect of cholinomimetics with aripiprazole and olanzapine, but enhances the effect in haloperidol and risperidone. Adding memantine to antipsychotics improves cognition except with quetiapine, an effect enhanced with smoking. Combining cholinomimetics, antipsychotics and memantine in general shows an additive effect, except for a negative interaction with aripiprazole and quetiapine and a synergistic effect with olanzapine and haloperidol in non-smokers and haloperidol in smokers. The complex interaction of cholinomimetics with memantine, antipsychotics and smoking can be quantitatively studied using mechanism-based advanced computer modeling. QSP modeling of virtual human patients can possibly generate useful insights on the non-linear interactions of multipharmacology drugs and support complex CNS R&D projects in cognition in search of synergistic polypharmacy.

Effects of antipsychotic D2 antagonists on long-term potentiation in animals and implications for human studies

In people with schizophrenia, cognitive abilities - including memory - are strongly associated with functional outcome. Long-term potentiation (LTP) is a form of neuroplasticity that is believed to be the physiological basis for memory. It has been postulated that antipsychotic medication can impair long-term potentiation and cognition by altering dopaminergic transmission. Thus, a systematic review was performed in order to assess the relationship between antipsychotics and D2 antagonists on long-term potentiation. The majority of studies on LTP and antipsychotics have found that acute administration of antipsychotics was associated with impairments in LTP in wild-type animals. In contrast, chronic administration and acute antipsychotics in animal models of schizophrenia were not. Typical and atypical antipsychotics and other D2 antagonists behaved similarly, with the exception of clozapine and olanzapine. Clozapine caused potentiation independent of tetanization, while olanzapine facilitated tetanus-induced potentiation. These studies are limited in their ability to model the effects of antipsychotics in patients with schizophrenia as they were largely performed in wild-type animals as opposed to humans with schizophrenia, and assessed after acute rather than chronic treatment. Further studies using patients with schizophrenia receiving chronic antipsychotic treatment are needed to better understand the effects of these medications in this population.

Open, randomized trial of the effects of aripiprazole versus risperidone on social cognition in schizophrenia

To date, only few studies have examined the impact of medication on social cognition and none have examined the effects of aripiprazole in this respect. The goal of this 8-week, randomized, multicenter, open-label study was to examine the effects of aripiprazole and risperidone on social cognition and neurocognition in individuals with schizophrenia. Eighty schizophrenia patients (DSM-IV-TR) aged 16-50 years were administered multiple computerized measures of social cognition and neurocognition including reaction times at baseline and the end of week 8. Social functioning was mapped with the Social Functioning scale and Quality of Life scale. The study ran from June 2005 to March 2011. Scores on social cognitive and neurocognitive tests improved with both treatments, as did reaction time. There were few differences between the two antipsychotics on (social) cognitive test-scores. The aripiprazole group performed better (more correct items) on symbol substitution (P=.003). Aripiprazole was also superior to risperidone on reaction time for emotional working memory and working memory (P=.006 and P=.023, respectively). Improvements on these tests were correlated with social functioning. In conclusion, aripiprazole and risperidone showed a similar impact on social cognitive test-scores. However, aripiprazole treatment produced a greater effect on patients' processing speed compared to risperidone, with these improvements being associated with concurrent improvements in social functioning. Further research on the long-term effects of aripiprazole on cognition is warranted.

Dopamine D2 receptor occupancy and cognition in schizophrenia: analysis of the CATIE data

INTRODUCTION

Antipsychotic drugs exert antipsychotic effects by blocking dopamine D2 receptors in the treatment of schizophrenia. However, effects of D2 receptor blockade on neurocognitive function still remain to be elucidated. The objective of this analysis was to evaluate impacts of estimated dopamine D2 receptor occupancy with antipsychotic drugs on several domains of neurocognitive function in patients with schizophrenia in the Clinical Antipsychotic Trials in Intervention Effectiveness (CATIE) trial.

METHODS

The dataset from the CATIE trial was used in the present analysis. Data were extracted from 410 subjects who were treated with risperidone, olanzapine, or ziprasidone, received assessments for neurocognitive functions (verbal memory, vigilance, processing speed, reasoning, and working memory) and psychopathology, and provided plasma samples for the measurement of plasma antipsychotic concentrations. D2 receptor occupancy levels on the day of neurocognitive assessment were estimated from plasma antipsychotic concentrations, using population pharmacokinetic analysis and our recently developed model. A multivariate general linear model was used to examine effects of clinical and demographic characteristics, including estimated D2 occupancy levels, on neurocognitive functions.

RESULTS

D2 occupancy levels showed significant associations with the vigilance and the summary scores. Neurocognitive functions, including vigilance, were especially impaired in subjects who showed D2 receptor occupancy level of >77%.

DISCUSSION

These findings suggest a nonlinear relationship between prescribed antipsychotic doses and overall neurocognitive function and vigilance. This study shows that D2 occupancy above approximately 80% not only increases the risk for extrapyramidal side effects as consistently reported in the literature but also increases the risk for cognitive impairment.

Effects of antipsychotic treatment on cognition in healthy subjects

Cognitive impairments can be observed in the majority of diseases with disturbed dopamine transmission. They are considered as core symptoms of schizophrenia, a disorder in which they appear to be particularly pronounced. Their neurobiological background is not yet sufficiently investigated, but dopaminergic systems are believed to play a crucial role. The aim of this single-blind, randomised, placebo-controlled study was to examine the effects of subchronic antidopaminergic treatment on cognitive functions in healthy subjects. In total, 72 healthy volunteers, randomised into four groups, received one antidopaminergic substance (aripiprazole, haloperidol or reserpine) or placebo, respectively, for 7 days. A comprehensive neurocognitive assessment was conducted at baseline, 24 h after the last medication intake and 7 days later. In the Digit Symbol Substitution Test a distinct, statistically significant improvement was measured in the second session in the placebo but not in the medication group. A significant group*time interaction for reaction times in three subtests of the Test battery for Attentional Performance (TAP) was also found. Our findings indicate that modulation of dopaminergic systems affects primarily speed of information processing, attention and learning. Absence of effects on other functions, differing from previous reports, may be an expression of a sufficient counter-regulation.

Interventions to reduce antipsychotic polypharmacy: a systematic review

BACKGROUND

It still remains unclear as to how to counteract antipsychotic polypharmacy that remains controversial but common. The objective of this study was to synthesize the clinical evidence to reduce antipsychotic polypharmacy (i.e. use of multiple antipsychotics) in schizophrenia.

METHODS

A literature search was performed to identify clinical trials that attempted to reduce antipsychotic polypharmacy in patients with schizophrenia by any form of systematic intervention using PubMed as well as MEDLINE, EMBASE, and PsycINFO (last search: June 2012). The search terms included "antipsychotics" and "polypharmacy". Cross-referencing was also performed.

RESULTS

The literature search identified 17 studies. Only 3 studies (1 randomized controlled trial and 2 open-label trials) were found that systematically switched antipsychotic polypharmacy to monotherapy. In two of them, more than two thirds of the subjects successfully completed the switch (40/58, 69.0%; 34/44, and 77.3%, respectively) while less than half the subjects tolerated it in the other study (6/14 and 42.9%) although the sample size was very small. On the other hand, 14 studies that examined impacts of interventions have physicians refrain from antipsychotic polypharmacy. While a modest intervention with educational approach alone was effective in three of the five articles, a more assertive intervention that directly cautioned physicians on the use of polypharmacy was effective in 10 of 12 articles.

CONCLUSION

The literature search revealed the paucity of the data. Careful switching from polypharmacy to monotherapy seems feasible in a majority of patients with schizophrenia. Assertive interventions, rather than passive educational approaches alone, appear more effective in reducing antipsychotic polypharmacy.

Cholinergic pathways and cognition in patients with schizophrenia: a pilot study

BACKGROUND

Cognitive deficits are core features in schizophrenia. Disruption in cholinergic neurotransmission has been associated with executive dysfunction in animals and humans. The objective of this study was to evaluate the impact of compromised cholinergic pathways on executive versus non-executive cognitive functions of patients with schizophrenia.

METHODS

62 patients with schizophrenia and 62 age- and sex-matched non-psychiatric control subjects ("controls") were assessed and compared using: clinical measures, cognitive measures of global cognition, executive function, and memory; and an MRI-based visual rating scale that assesses damage strategically localized within the cholinergic pathways.

RESULTS

11 of the 62 patients with schizophrenia (17.7%) and 6 of the 62 controls (9.7%) had compromised cholinergic pathways. These proportions were not statistically significant. Patients and controls with compromised cholinergic pathways were more impaired on measures related to executive function than patients or controls without compromised pathways.

CONCLUSIONS

Patients with schizophrenia have worse executive function than controls. Compromised cholinergic pathways appear to worsen the executive dysfunction observed in schizophrenia. If these preliminary findings are replicated, they could lead to the identification of a subgroup of patients with schizophrenia who could specifically benefit from interventions enhancing cholinergic neurotransmission.

Management of schizophrenia in late life with antipsychotic medications: a qualitative review

Although patients with schizophrenia are reported to have excess mortality compared with the general population, many affected patients will nonetheless survive and continue to have the disorder in later life. Consequently, geriatric schizophrenia will be a significant public health concern in the years to come, and evidence-based treatment of schizophrenia in older patients is becoming an urgent issue. However, there has been a paucity of comparative data to guide selection of antipsychotics for schizophrenia in late life. The primary aim of this review was to synthesize the available evidence on management of late-life schizophrenia with antipsychotic medications; a secondary aim was to evaluate treatment resistance in this population. Accordingly, PubMed and EMBASE were searched using the keywords 'antipsychotics', 'age' and 'schizophrenia' to identify psychopharmacological studies of antipsychotics in late-life schizophrenia (last search 30 April 2011). The literature search identified 23 prospective studies of use of antipsychotics for schizophrenia in older patients (generally age ≥65 years), including eight double-blind trials. The sample size was smaller than 40 patients for 52% of the studies. Two of the double-blind studies were post hoc analyses and one was a placebo-controlled trial. In the largest double-blind study, olanzapine (n = 88, median dose 10 mg/day) and risperidone (n = 87, median dose 2 mg/day) were compared in patients not resistant to these therapies, with similar effects. There have also been several open-label trials of these two agents that have shown efficacy and tolerability in non-resistant patients. Evidence on other antipsychotics has been scarce and less robust. The gold standard for treatment-resistant schizophrenia is clozapine. However, almost all of the studies of clozapine to date have effectively excluded older patients with schizophrenia. Only one small study has evaluated clozapine (n = 24, mean dose 300 mg/day) in comparison with chlorpromazine (n = 18, mean dose 600 mg/day) in a difficult-to-treat older population; the investigators reported that both treatments were similarly efficacious. Furthermore, there has been little compelling evidence in favour of or against augmentation of antipsychotics with other psychotropic medications in the older age group. Treatment of non-resistant, late-life schizophrenia with olanzapine and risperidone appears to be supported by the available evidence. However, data on geriatric patients with schizophrenia are generally scarce, particularly for treatment-resistant subpopulations, underscoring the need for more research in this important area.

Dopamine D2 receptor occupancy and clinical effects: a systematic review and pooled analysis

Positron emission tomography (PET) studies proposed a therapeutic window of D2 receptor occupancy (65%-80%) of antipsychotics for the treatment of schizophrenia in young adults. However, this conclusion has been drawn from clinical PET studies using small sample sizes (<20). Prospective PET studies that measured D2 occupancy levels and assessed extrapyramidal side effects (EPS) and/or treatment response induced by antipsychotics (excluding partial agonists) were identified, using MEDLINE and EMBASE (last search: March 2010). Individual subjects were divided into 2 groups based on EPS status (ie, presence or lack of newly emergent EPS) and treatment response (ie, a ≥ 25% or ≥ 50% reduction in the Positive and Negative Syndrome Scale or Brief Psychiatric Rating Scale). To evaluate the performance of this binary classification, sensitivity, specificity, and accuracy of consecutive cutoff points in the D2 occupancy were calculated: Accuracy = (True Positive + True Negative) / Total N. Twelve studies, including a total of 82 subjects, were included in our analyses. The cutoff points associated with 0.5 or greater in both sensitivity and specificity with the greatest accuracy were 77% to 78% for EPS, 60% for a 25% or greater symptom reduction, and 72% for a 50% or greater symptom reduction. These findings support the presence of a therapeutic window of 60% to 78% D2 occupancy of antipsychotics in young adults with schizophrenia and may suggest the presence of a continuum of effectiveness with increasing occupancy within this therapeutic window.

Enhanced control of attention by stimulating mesolimbic-corticopetal cholinergic circuitry

Sustaining and recovering attentional performance requires interactions between the brain's motivation and attention systems. The first experiment demonstrated that in rats performing a sustained attention task (SAT), presentation of a distractor (dSAT) augmented performance-associated increases in cholinergic neurotransmission in prefrontal cortex. Because stimulation of NMDA receptors in the shell of the nucleus accumbens activates PFC cholinergic neurotransmission, a second experiment demonstrated that bilateral infusions of NMDA into the NAc shell, but not core, improved dSAT performance to levels observed in the absence of a distractor. A third experiment demonstrated that removal of prefrontal or posterior parietal cholinergic inputs, by intracortical infusions of the cholinotoxin 192 IgG-saporin, attenuated the beneficial effects of NMDA on dSAT performance. Mesolimbic activation of cholinergic projections to the cortex benefits the cognitive control of attentional performance by enhancing the detection of cues and the filtering of distractors.

A tipping point in drug dosing in late-life schizophrenia

Minimally effective doses of antipsychotics are likely influenced by several clinical and demographic characteristics of patients, with age being one of the most important elements. In light of age-related physiologic changes as well as interindividual differences in pharmacokinetic and pharmacodynamic systems, individualized dosing with regard to age will be critically important for safer drug treatment for older patients with schizophrenia. In the present review, we propose the following cautious psychopharmacologic interventions for this population: 1) simple regimen (avoid polypharmacy), 2) be aware of the presence of patients who are very sensitive to drugs, 3) gradual dose titration, and 4) timely and thorough assessments of therapeutic and side effects. The age-related antipsychotic sensitivity highlights the importance of finding the lowest possible effective dose of antipsychotic drugs as patients with schizophrenia age to maximize therapeutic effects and minimize side effects.

Clinical and demographic characteristics associated with postural instability in patients with schizophrenia

As people with schizophrenia grow older, prevention of falls in this older population has become a public health priority. It is therefore critically important to identify risk factors to effectively prevent falls. For this purpose, the degree of postural sway can serve as a convenient index of risk assessment. The objective of this study was to find clinical and demographic characteristics associated with postural instability. Inpatients and outpatients with schizophrenia or related psychosis were recruited at 2 hospitals in Japan. The clinical stabilometric platform, which measured a range of the trunk motion, and extrapyramidal side effects were evaluated between 9 and 11 A.M. Four hundred two subjects were enrolled (age: mean, 55.5 [SD, 14.4] years). A univariate general linear model showed that the use of antipsychotic drugs with a chlorpromazine equivalent of 10 or greater, being overweight, and inpatient treatment setting were associated with a greater degree of the range of postural sway. Another general linear model, including a subgroup of 300 subjects who did not present any extrapyramidal side effects, not only consolidated these findings, but also revealed a great degree of postural sway in older subjects. In addition, quetiapine was found to be associated with a greater range of postural sway among atypical antipsychotics. Schizophrenia patients generally showed a greater degree of postural instability, compared with the reference data of healthy people. These findings highlight truncal instability as a risk factor of falls in patients with schizophrenia, especially when they are overweight, old, and/or receiving antipsychotics with a chlorpromazine equivalent of 10 or greater, including quetiapine.

QSAR-CoMSIA applied to antipsychotic drugs with their dopamine D2 and serotonine 5HT2A membrane receptors

Antipsychotic drugs are psychiatric medication primarily used to manage psychosis (e.g., delusions or hallucinations), particularly in schizophrenia and bipolar disorder. First and second generations of antipshychotics tend to block receptors in the brain's dopamine pathways, but antipsychotic drugs encompass a wide range of receptor targets. The inhibition constant, Ki, at the level of membrane receptors is a major determinant of their pharmacokinetic behavior and, consequently, it can affect their antipsychotic activity. Here, predicted inhibition constants, Ki for 71 antipsychotics, already approved for clinical treatment, as well as representative new chemical structures which exhibit antipsychotic activity, were evaluated using 3D-QSAR-CoMSIA models. Significant values of the cross-validated correlation q2 (higher than 0.70) and the fitted correlation r2 (higher than 0.80) revealed that these models have reasonable power to predict the biological affinity of the 15 new risperidone and 12 new olanzapine derivatives in interactions with dopamine D2 and serotonin 5HT2A receptors; these compounds are suggested for further studies.

Cholinergic contributions to the cognitive symptoms of schizophrenia and the viability of cholinergic treatments

Effective treatment of the cognitive symptoms of schizophrenia has remained an elusive goal. Despite the intense focus on treatments acting at or via cholinergic mechanisms, little remains known about the dynamic cholinergic abnormalities that contribute to the manifestation of the cognitive symptoms in patients. Evidence from basic neuroscientific and psychopharmacological investigations assists in proposing detailed cholinergic mechanisms and treatment targets for enhancement of attentional performance. Dynamic, cognitive performance-dependent abnormalities in cholinergic activity have been observed in animal models of the disorder and serve to further refine such proposals. Finally, the potential usefulness of individual groups of cholinergic drugs and important issues concerning the interactions between pro-cholinergic and antipsychotic treatments are addressed. The limited evidence available from patient studies and animal models indicates pressing research needs in order to guide the development of cholinergic treatments of the cognitive symptoms of schizophrenia.

Sensitivity to antipsychotic drugs in older adults

Antipsychotic medications are widely used to manage psychotic and behavioral disorders in older adults, including primary psychotic disorders such as schizophrenia, and psychosis and behavioral disturbances associated with dementia. These two broad diagnostic indications are associated with contrasting recommended treatment durations, with the former requiring indefinite treatment across the life span. Antipsychotic drug dosing for schizophrenia is based primarily on studies of younger patients and thus may not apply to older adults. It is critically important to address the effects of aging on antipsychotic dosing given the recent emergence of data that suggest a critical role for age-related sensitivity to these drugs. Antipsychotic drugs are not only associated with somatic and neurological adverse effects but also increased all-cause mortality and sudden cardiac death in this vulnerable population. This review focuses on the sensitivity of older adults to adverse effects from antipsychotic medications and the current pharmacokinetic and pharmacodynamic explanatory models of susceptibility. Implications of recent research findings for individualized pharmacotherapy are discussed.