Antipsychotic-induced prolactin elevation in premenopausal women with schizophrenia: associations with estrogen, disease severity and cognition.

PURPOSE: Antipsychotic-induced prolactin elevation may impede protective effects of estrogens in women with schizophrenia-spectrum disorders (SSD). Our study sought to confirm whether the use of prolactin-raising antipsychotics is associated with lower estrogen levels, and to investigate how estrogen and prolactin levels relate to symptom severity and cognition in premenopausal women with SSD. METHODS: This cross-sectional study included 79 premenopausal women, divided in three groups of women with SSD treated with prolactin-sparing antipsychotics (n = 21) or prolactin-raising antipsychotics (n = 27), and age-matched women without SSD (n = 31). Circulating 17ß-estradiol was compared among groups. In patients, we assessed the relationship between prolactin and 17ß-estradiol, and the relationships of these hormones to symptom severity and cognition, using correlation analyses and backward regression models. RESULTS: In women receiving prolactin-raising antipsychotics, 17ß-estradiol levels were lower as compared to both other groups (H(2) = 8.34; p = 0.015), and prolactin was inversely correlated with 17ß-estradiol (r=-0.42, p = 0.030). In the prolactin-raising group, 17ß-estradiol correlated positively with verbal fluency (r = 0.52, p = 0.009), and 17ß-estradiol and prolactin together explained 29% of the variation in processing speed (ß17ß-estradiol = 0.24, ßprolactin = -0.45, F(2,25) = 5.98, p = 0.008). In the prolactin-sparing group, 17ß-estradiol correlated negatively with depression/anxiety (r = -0.57, p = 0.014), and together with prolactin explained 26% of the variation in total symptoms (ß17ß-estradiol = -0.41, ßprolactin = 0.32, F(2,18) = 4.44, p = 0.027). CONCLUSIONS: In women with SSD, antipsychotic-induced prolactin elevation was related to lower estrogen levels. Further, estrogens negatively correlated with symptom severity and positively with cognition, whereas prolactin levels correlated negatively with cognition. Our findings stress the clinical importance of maintaining healthy levels of prolactin and estrogens in women with SSD.

Shared effects of electroconvulsive shocks and ketamine on neuroplasticity: A systematic review of animal models of depression.

Electroconvulsive shocks (ECS) and ketamine are antidepressant treatments with a relatively fast onset of therapeutic effects compared to conventional medication and psychotherapy. While the exact neurobiological mechanisms underlying the antidepressant response of ECS and ketamine are unknown, both interventions are associated with neuroplasticity. Restoration of neuroplasticity may be a shared mechanism underlying the antidepressant efficacy of these interventions. In this systematic review, literature of animal models of depression is summarized to examine the possible role of neuroplasticity in ECS and ketamine on a molecular, neuronal, synaptic and functional level, and specifically to what extent these mechanisms are shared between both interventions. The results highlight that hippocampal neurogenesis and brain-derived neurotrophic factor (BDNF) levels are consistently increased after ECS and ketamine. Moreover, both interventions positively affect glutamatergic neurotransmission, astrocyte and neuronal morphology, synaptic density, vasculature and functional plasticity. However, a small number of studies investigated these processes after ECS. Understanding the shared fundamental mechanisms of fast-acting antidepressants can contribute to the development of novel therapeutic approaches for patients with severe depression.

Cholinergic deficiency in Parkinson's disease patients with visual hallucinations.

Visual hallucinations (VH) can increase the burden of disease for both patients with Parkinson's disease (PD) and their caregivers. Multiple neurotransmitters have been implicated in the neuropathology of VH, which provide targets for treatment and prevention. In this study, we assessed the association between cholinergic denervation and VH in PD in vivo, using PET imaging of the cholinergic system. A total of 38 PD patients participated in this study. A group of 10 healthy subjects, matched for age, sex and education, was included for comparison. None of the participants used cholinergic drugs. Thirteen patients who had experienced VH in the past month (VH+) were compared to 20 patients who had never experienced VH in their lives (VH-). Cholinergic system integrity was assessed with PET imaging using [18F]fluoroethoxybenzovesamicol ([18F]FEOBV) as the tracer. We assessed the differences in tracer uptake between groups by cluster-based analysis and by analysis of predefined regions of interest (ROIs) consisting of the ventral visual stream, the dorsal attentional network, the ventral attentional network and the lateral geniculate nucleus and mediodorsal nucleus of the thalamus. The PD group (n=38) showed an extensive pattern of decreased tracer uptake throughout the brain, compared to the controls (n=10). Within the PD group, the VH+ group (n=13) showed a cluster of decreased tracer uptake compared to the VH- group (n=20), which covered most of the left ventral visual stream and extended towards superior temporal areas. These results were mirrored in the ROI-based analysis, where the VH+ group showed the strongest deficits in the left inferior temporal gyrus and the left superior temporal gyrus, compared to the VH- group. VH in PD are associated with a marked cholinergic deficiency in the left ventral visual stream and the left superior temporal lobe, in addition to an extensive global cholinergic denervation in the general PD population.

The association of prolactin and gonadal hormones with cognition and symptoms in men with schizophrenia spectrum disorder: Divergent effects of testosterone and estrogen.

BACKGROUND: Certain antipsychotics elevate prolactin levels in patients with schizophrenia spectrum disorders (SSD), potentially affecting cognition, symptoms, and hormone levels. This study examines the association between prolactin, testosterone, and estrogen and cognition and symptoms in men with SSD, considering antipsychotic medication. METHODS: This cross-sectional study included 128 men with SSD and 44 healthy men from two trials. Patients were divided into a prolactin-sparing (n = 53) and prolactin-raising group (n = 75) based on antipsychotic medication. We examined the association between hormones (testosterone, estrogen and prolactin), and cognition and symptoms using backward linear regression. Three domains of cognition were assessed including: processing speed, verbal fluency, and working memory, while symptoms were measured using the Positive and Negative Syndrome Scale (PANSS). RESULTS: Prolactin levels were highest in the prolactin-raising group, followed by the control group, and lowest in the prolactin-sparing group (H = 45.279, p < .001). Testosterone and estrogen levels did not differ significantly between groups. In the prolactin-raising group, prolactin negatively correlated with testosterone (r(73) = -0.32, p = .005). Higher testosterone predicted better cognitive functioning (working memory: ß = 0.20, p = .007, verbal fluency: ß = 0.30, p = .001) and lower symptom scores (total: ß = -0.21, p = .001; negative: ß = -0.24, p = .002) in men with SSD. Conversely, higher estrogen levels related to slower processing speed (ß = -0.22, p < .001) and higher symptoms scores (ß = 0.23, p = .010) in men with SSD. CONCLUSION: The results suggest positive associations between testosterone and cognition and symptoms in men with SSD, while suggesting that high prolactin levels could relate to lower testosterone levels, possibly worsening cognition and symptoms in men with SSD.

Postpartum Psychosis: A Proposed Treatment Algorithm.

Background: Postpartum psychosis (PPP) is a psychiatric emergency that generally warrants acute inpatient care. PPP is marked by the sudden onset of affective and psychotic symptoms with a rapid deterioration in mental state. Evidence suggests that PPP is a discrete disorder on the bipolar disorder spectrum with a distinct treatment profile and prognosis. Methods: We conducted a PubMed database search for various terms involving PPP and its treatment and included peer-reviewed articles published in English. Objective: To provide a treatment algorithm for the management of PPP based on available evidence. Results: Pharmacological therapy is the mainstay of PPP management in the acute phase. Evidence points to a combination of antipsychotics and lithium in the acute treatment of PPP. Electroconvulsive therapy can offer a rapid treatment response where required. Lithium appears to have the best evidence for relapse prevention and prophylaxis in PPP. Psychoeducation is essential and psychosocial interventions used in bipolar disorder may be effective in PPP. Conclusion: Early detection and prompt treatment with antipsychotics and lithium, followed by maintenance treatment with lithium, is associated with a favourable prognosis in PPP.Reprinted from J Psychopharmacol 2023; 37:960-970, with permission from Sage Journals. Copyright © 2023.

The experience of felt presence in a general population sample.

Felt presence is a widely occurring experience, but remains under-recognised in clinical and research practice. To contribute to a wider recognition of the phenomenon, we aimed to assess the presentation of felt presence in a large population sample (n = 10 447) and explore its relation to key risk factors for psychosis. In our sample 1.6% reported experiencing felt presence in the past month. Felt presence was associated with visual and tactile hallucinations and delusion-like thinking; it was also associated with past occurrence of adverse events, loneliness and poor sleep. The occurrence of felt presence may function as a marker for general hallucination proneness.

Exploring peripheral biomarkers of response to simvastatin supplementation in schizophrenia.

Schizophrenia is one of the most debilitating mental disorders, and its diagnosis and treatment present significant challenges. Several clinical trials have previously evaluated the effectiveness of simvastatin, a lipid-lowering medication, as a novel add-on treatment for schizophrenia. However, treatment effects varied highly between patients and over time. In the present study, we aimed to identify biomarkers of response to simvastatin in recent-onset schizophrenia patients. To this end, we profiled relevant immune and metabolic markers in patient blood samples collected in a previous clinical trial (ClinicalTrials.gov: NCT01999309) before simvastatin add-on treatment was initiated. Analysed sample types included serum, plasma, resting-state peripheral blood mononuclear cells (PBMCs), as well as PBMC samples treated ex vivo with immune stimulants and simvastatin. Associations between the blood readouts and clinical endpoints were evaluated using multivariable linear regression. This revealed that changes in insulin receptor (IR) levels induced in B-cells by ex vivo simvastatin treatment inversely correlated with in vivo effects on cognition at the primary endpoint of 12 months, as measured using the Brief Assessment of Cognition in Schizophrenia scale total score (standardised ß ± SE = -0.75 ± 0.16, P = 2.2 × 10-4, Q = 0.029; n = 21 patients). This correlation was not observed in the placebo group (ß ± SE = 0.62 ± 0.39, P = 0.17, Q = 0.49; n = 14 patients). The candidate biomarker explained 53.4 % of the variation in cognitive outcomes after simvastatin supplementation. Despite the small sample size, these findings suggest a possible interaction between the insulin signalling pathway and cognitive effects during simvastatin therapy. They also point to opportunities for personalized schizophrenia treatment through patient stratification.

Short-latency afferent inhibition as a biomarker of cholinergic degeneration compared to PET imaging in Parkinson's disease.

INTRODUCTION: Short-latency afferent inhibition (SAI) is a relatively cheap and non-invasive method that has been proposed as a cholinergic marker in Parkinson's disease (PD). We aim to verify the clinical feasibility of SAI as a cholinergic marker in PD using positron emission tomography (PET) with the tracer (2R,3R)-5-(2-[18F]fluoroethoxy)benzovesamicol ([18F]FEOBV) as a reference. METHODS: We examined relations between SAI and [18F]FEOBV PET using linear regression analysis, with the primary motor cortex (M1) as primary region of interest. Additionally, we examined relations of both measures with clinical features. RESULTS: 30 PD patients with varying degrees of cognitive dysfunction and 10 healthy controls (HC) were included in the analysis. SAI was not related to tracer uptake in M1 in the PD group (p = .291) or the HC group (p = .206). We could not replicate the previously published relations between SAI and cholinergic symptoms, such as cognition, psychotic experiences and olfactory function. CONCLUSION: SAI was not related to [18F]FEOBV imaging parameters, nor to clinical measures of cholinergic dysfunction. Therefore, SAI may not be feasible as a clinically applied cholinergic marker in PD.

Multisensory hallucinations and other unusual sensory experiences in the context of migraine: a systematic review.

OBJECTIVE AND BACKGROUND: Visual auras in migraine have been extensively studied, but less is known about multisensory hallucinations or other unusual sensory experiences, including whether these should be diagnostically considered as part of aura symptoms. The current study aimed to conduct a systematic review and synthesis to bring together existing empirical evidence on these non-visual perceptual experiences, focusing on their phenomenological descriptions and clinical correlates. METHODS: Forty-eight relevant studies were included based on a systematic search across PsycINFO APA and Web of Science, for peer-reviewed publications in the English language, from 1980 to the present. These comprised a mix of case reports/series (n = 19) and group design studies (n = 29). RESULTS: Reports of complex multisensory hallucinations, beyond typical established aura symptoms, were numerous and varied in nature. Yet there were limited data on how this related to patient distress and functional interference. Other sensory distortions or hypersensitivities across non-visual domains were also evident, and generally more common in those with established aura symptoms. CONCLUSION: Our findings provide preliminary evidence that multisensory hallucinations and other unusual perceptual experiences in migraine are likely more common than previously believed. Further investigations are needed to appropriately account for these symptoms within current nosological systems. Increased clinician-patient awareness is important for managing distress (where necessary), and potentially for offering a holistic therapeutic approach to migraine management.

Personal preferences for treatment and care during and after a First Episode Psychosis: A qualitative study.

AIM: A first episode of psychosis (FEP) is a stressful, often life-changing experience. Scarce information is available about personal preferences regarding their care needs during and after a FEP. Whereas a more thorough understanding of these preferences is essential to aid shared decision-making during treatment and improve treatment satisfaction. METHODS: Face-to-face interviews with participants in remission of a FEP were set up, addressing personal preferences and needs for care during and after a FEP. The interviews were conducted by a female and a male researcher, the latter being an expert with lived experience. RESULTS: Twenty individuals in remission of a FEP were interviewed, of which 16 had been hospitalized. The distinguished themes based on personal preferences were tranquillity, peace and quietness, information, being understood, support from significant others, and practical guidance in rebuilding one's life. Our findings revealed that the need for information and the need to be heard were often not sufficiently met. For 16/20 participants, the tranquillity of inpatient treatment of the FEP was predominantly perceived as a welcome safe haven. The presence and support of family and close friends were mentioned as an important factor in the process of achieving remission. CONCLUSIONS: The current exploratory study showed that patients were able to indicate their personal needs. Important findings are the need for information and the need to be heard. Interestingly, hospitalization was mostly seen as an opportunity to achieve tranquillity. More lived experience expertise is needed to elucidate the needs of individuals in the early phase of a FEP to aid people who are recovering from their first psychosis in rebuilding their lives again.

Evidence-Based Recommendations for the Pharmacological Treatment of Women with Schizophrenia Spectrum Disorders.

PURPOSE OF REVIEW: Despite clear evidence that sex differences largely impact the efficacy and tolerability of antipsychotic medication, current treatment guidelines for schizophrenia spectrum disorders (SSD) do not differentiate between men and women. This review summarizes the available evidence on strategies that may improve pharmacotherapy for women and provides evidence-based recommendations to optimize treatment for women with schizophrenia. RECENT FINDINGS: We systematically searched PubMed and Embase for peer-reviewed studies on three topics: (1) sex differences in dose-adjusted antipsychotic serum concentrations, (2) hormonal augmentation therapy with estrogen and estrogen-like compounds to improve symptom severity, and (3) strategies to reduce antipsychotic-induced hyperprolactinemia. Based on three database studies and one RCT, we found higher dose-adjusted concentrations in women compared to men for most antipsychotics. For quetiapine, higher concentrations were specifically found in older women. Based on two recent meta-analyses, both estrogen and raloxifene improved overall symptomatology. Most consistent findings were found for raloxifene augmentation in postmenopausal women. No studies evaluated the effects of estrogenic contraceptives on symptoms. Based on two meta-analyses and one RCT, adjunctive aripiprazole was the best-studied and safest strategy for lowering antipsychotic-induced hyperprolactinemia. Evidence-based recommendations for female-specific pharmacotherapy for SSD consist of (1) female-specific dosing for antipsychotics (guided by therapeutic drug monitoring), (2) hormonal replacement with raloxifene in postmenopausal women, and (3) aripiprazole addition as best evidenced option in case of antipsychotic-induced hyperprolactinemia. Combining these strategies could reduce side effects and improve outcome of women with SSD, which should be confirmed in future longitudinal RCTs.

Adjunctive agents to antipsychotics in schizophrenia: a systematic umbrella review and recommendations for amino acids, hormonal therapies and anti-inflammatory drugs.

QUESTION: This umbrella review and guidelines aimed to provide evidence to support the rational choice of selected adjunctive therapies for schizophrenia. STUDY SELECTION AND ANALYSIS: Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and World Federation of Societies of Biological Psychiatry (WFSBP)-grading recommendations, 63 randomised control trials (RCTs) (of which 4219 unique participants have completed the RCTs) and 29 meta-analyses were analysed. FINDINGS: Provisional recommendations (WFSBP-grade 1) could be made for two molecules in augmentation to antipsychotics: (1) N-acetyl-cysteine (NAC, 1200-3600 mg/day, for >12 consecutive weeks) in improving negative symptoms, general psychopathology (positive and negative syndrome scale for schizophrenia (PANSS) general psychopathology factor (G)-G subscale), with the RCTs with the longer duration showing the most robust findings; (2) polyunsaturated fatty acids (3000 mg/day of eicosapentaenoic acid, for >12 weeks) in improving general psychopathology. Weaker recommendations (ie, WFSBP-grade 2) could be drawn for sarcosine (2 g/day) and minocycline (200-300 mg/day) for improving negative symptoms in chronic schizophrenia (not early schizophrenia), and NAC for improving positive symptoms and cognition. Weak recommendations are not ready for clinical practice. There is provisional evidence that oestrogens and raloxifene are effective in some patients, but further research is needed to determine their benefit/risk ratio. CONCLUSIONS: The results of this umbrella review should be interpreted with caution as the number of RCTs included in the meta-analyses was generally small and the effect sizes were weak or medium. For NAC, two RCTs with low risk of bias have provided conflicting results and the WFSBP-grade recommendation included also the results of meta-analyses. These drugs could be provisionally prescribed for patients for whom no other treatments have been effective, but they should be discontinued if they prove ineffective.

Moment-to-moment affective dynamics in schizophrenia and bipolar disorder.

BACKGROUND: Affective disturbances in schizophrenia and bipolar disorder may represent a transdiagnostic etiological process as well as a target of intervention. Hypotheses on similarities and differences in various parameters of affective dynamics (intensity, successive/acute changes, variability, and reactivity to stress) between the two disorders were tested. METHODS: Experience sampling method was used to assess dynamics of positive and negative affect, 10 times a day over 6 consecutive days. Patients with schizophrenia (n = 46) and patients with bipolar disorder (n = 46) were compared against age-matched healthy controls (n = 46). RESULTS: Compared to controls, the schizophrenia group had significantly more intense momentary negative affect, a lower likelihood of acute changes in positive affect, and reduced within-person variability of positive affect. The bipolar disorder group was not significantly different from either the schizophrenia group or the healthy control group on any affect indexes. Within the schizophrenia group, level of depression was associated with weaker reactivity to stress for negative affect. Within the bipolar disorder group, level of depression was associated with lower positive affect. CONCLUSIONS: Patients with schizophrenia endured a more stable and negative affective state than healthy individuals, and were less likely to be uplifted in response to happenings in daily life. There is little evidence that these affective constructs characterize the psychopathology of bipolar disorder; such investigation may have been limited by the heterogeneity within group. Our findings supported the clinical importance of assessing multiple facets of affective dynamics beyond the mean levels of intensity.

The association of childhood trauma with depressive and negative symptoms in recent onset psychosis: a sex-specific analysis.

BACKGROUND: Childhood trauma may impact the course of schizophrenia spectrum disorders (SSD), specifically in relation to the increased severity of depressive or negative symptoms. The type and impact of trauma may differ between sexes. In a large sample of recent-onset patients, we investigated the associations of depressive and negative symptoms with childhood trauma and whether these are sex-specific. METHODS: A total of 187 first-episode psychosis patients in remission (Handling Antipsychotic Medication: Long-term Evaluation of Targeted Treatment study) and 115 recent-onset SSD patients (Simvastatin study) were included in this cross-sectional study (men: n = 218; women: n = 84). Total trauma score and trauma subtypes were assessed using the Childhood Trauma Questionnaire Short Form; depressive and negative symptoms were rated using the Positive And Negative Symptoms Scale. Sex-specific regression analyses were performed. RESULTS: Women reported higher rates of sexual abuse than men (23.5% v. 7.8%). Depressive symptoms were associated with total trauma scores and emotional abuse ratings in men (ß: 0.219-0.295; p ≤ 0.001). In women, depressive symptoms were associated with sexual abuse ratings (ß: 0.271; p = 0.011). Negative symptoms were associated with total trauma score and emotional neglect ratings in men (ß: 0.166-0.232; p ≤ 0.001). Negative symptoms in women were not linked to childhood trauma, potentially due to lack of statistical power. CONCLUSIONS: Depressive symptom severity was associated with different types of trauma in men and women with recent-onset SSD. Specifically, in women, depressive symptom severity was associated with childhood sexual abuse, which was reported three times as often as in men. Our results emphasize the importance of sex-specific analyses in SSD research.

Postpartum psychosis: A proposed treatment algorithm.

BACKGROUND: Postpartum psychosis (PPP) is a psychiatric emergency that generally warrants acute inpatient care. PPP is marked by the sudden onset of affective and psychotic symptoms with a rapid deterioration in mental state. Evidence suggests that PPP is a discrete disorder on the bipolar disorder spectrum with a distinct treatment profile and prognosis. METHODS: We conducted a PubMed database search for various terms involving PPP and its treatment and included peer-reviewed articles published in English. OBJECTIVE: To provide a treatment algorithm for the management of PPP based on available evidence. RESULTS: Pharmacological therapy is the mainstay of PPP management in the acute phase. Evidence points to a combination of antipsychotics and lithium in the acute treatment of PPP. Electroconvulsive therapy can offer a rapid treatment response where required. Lithium appears to have the best evidence for relapse prevention and prophylaxis in PPP. Psychoeducation is essential and psychosocial interventions used in bipolar disorder may be effective in PPP. CONCLUSION: Early detection and prompt treatment with antipsychotics and lithium, followed by maintenance treatment with lithium, is associated with a favourable prognosis in PPP.

An international research agenda for clozapine-resistant schizophrenia.

Treatment-resistant symptoms occur in about a third of patients with schizophrenia and are associated with a substantial reduction in their quality of life. The development of new treatment options for clozapine-resistant schizophrenia constitutes a crucial, unmet need in psychiatry. Additionally, an overview of past and possible future research avenues to optimise the early detection, diagnosis, and management of clozapine-resistant schizophrenia is unavailable. In this Health Policy, we discuss the ongoing challenges associated with clozapine-resistant schizophrenia faced by patients and health-care providers worldwide to improve the understanding of this condition. We then revisit several clozapine guidelines, the diagnostic tests and treatment options for clozapine-resistant schizophrenia, and currently applied research approaches in clozapine-resistant schizophrenia. We also suggest methodologies and targets for future research, divided into innovative nosology-oriented field trials (eg, examining dimensional symptom staging), translational approaches (eg, genetics), epidemiological research (eg, real-world studies), and interventional studies (eg, non-traditional trial designs incorporating lived experiences and caregivers' perspectives). Finally, we note that low-income and middle-income countries are under-represented in studies on clozapine-resistant schizophrenia and propose an agenda to guide multinational research on the cause and treatment of clozapine-resistant schizophrenia. We hope that this research agenda will empower better global representation of patients living with clozapine-resistant schizophrenia and ultimately improve their functional outcomes and quality of life.

Cholinesterase Inhibitors for Treatment of Psychotic Symptoms in Alzheimer Disease and Parkinson Disease: A Meta-analysis.

Importance: Psychotic symptoms greatly increase the burden of disease for people with neurodegenerative disorders and their caregivers. Cholinesterase inhibitors (ChEIs) may be effective treatment for psychotic symptoms in these disorders. Previous trials only evaluated neuropsychiatric symptoms as a secondary and an overall outcome, potentially blurring the outcomes noted with ChEI use specifically for psychotic symptoms. Objective: To quantitatively assess the use of ChEIs for treatment of individual neuropsychiatric symptoms, specifically hallucinations and delusions, in patients with Alzheimer disease (AD), Parkinson disease (PD), and dementia with Lewy bodies (DLB). Data Sources: A systematic search was performed in PubMed (MEDLINE), Embase, and PsychInfo, without year restrictions. Additional eligible studies were retrieved from reference lists. The final search cutoff date was April 21, 2022. Study Selection: Studies were selected if they presented the results of placebo-controlled randomized clinical trials, including at least 1 donepezil, rivastigmine, or galantamine treatment arm in patients with AD, PD, or DLB; if they applied at least 1 neuropsychiatric measure including hallucinations and/or delusions; and if a full-text version of the study was available in the English language. Study selection was performed and checked by multiple reviewers. Data Extraction and Synthesis: Original research data were requested on eligible studies. A 2-stage meta-analysis was then performed, using random-effects models. Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines were followed for extracting data and assessing the data quality and validity. Data extraction was checked by a second reviewer. Main Outcomes and Measures: Primary outcomes were hallucinations and delusions; secondary outcomes included all other individual neuropsychiatric subdomains as well as the total neuropsychiatric score. Results: In total, 34 eligible randomized clinical trials were selected. Individual participant data on 6649 individuals (3830 [62.6%] women; mean [SD] age, 75.0 [8.2] years) were obtained from 17 trials (AD: n = 12; PD: n = 5; individual participant data were not available for DLB). An association with ChEI treatment was shown in the AD subgroup for delusions (-0.08; 95% CI, -0.14 to -0.03; P = .006) and hallucinations (-0.09; 95% CI, -0.14 to -0.04; P = .003) and in the PD subgroup for delusions (-0.14; 95% CI, -0.26 to -0.01; P = .04) and hallucinations (-0.08, 95% CI -0.13 to -0.03; P = .01). Conclusions and Relevance: The results of this individual participant data meta-analysis suggest that ChEI treatment improves psychotic symptoms in patients with AD and PD with small effect sizes.