A cross ancestry genetic study of psychiatric disorders from India.

Genome-wide association studies across diverse populations may help validate and confirm genetic contributions to risk of disease. We estimated the extent of population stratification as well as the predictive accuracy of polygenic scores (PGS) derived from European samples to a data set from India. We analysed 2685 samples from two data sets, a population neurodevelopmental study (cVEDA) and a hospital-based sample of bipolar affective disorder (BD) and obsessive-compulsive disorder (OCD). Genotyping was conducted using Illumina's Global Screening Array. Population structure was examined with principal component analysis (PCA), uniform manifold approximation and projection (UMAP), support vector machine (SVM) ancestry predictions, and admixture analysis. PGS were calculated from the largest available European discovery GWAS summary statistics for BD, OCD, and externalizing traits using two Bayesian methods that incorporate local linkage disequilibrium structures (PGS-CS-auto) and functional genomic annotations (SBayesRC). Our analyses reveal global and continental PCA overlap with other South Asian populations. Admixture analysis revealed a north-south genetic axis within India (FST 1.6%). The UMAP partially reconstructed the contours of the Indian subcontinent. The Bayesian PGS analyses indicates moderate-to-high predictive power for BD. This was despite the cross-ancestry bias of the discovery GWAS dataset, with the currently available data. However, accuracy for OCD and externalizing traits was much lower. The predictive accuracy was perhaps influenced by the sample size of the discovery GWAS and phenotypic heterogeneity across the syndromes and traits studied. Our study results highlight the accuracy and generalizability of newer PGS models across ancestries. Further research, across diverse populations, would help understand causal mechanisms that contribute to psychiatric syndromes and traits.

Altered neuroepithelial morphogenesis and migration defects in iPSC-derived cerebral organoids and 2D neural stem cells in familial bipolar disorder.

Bipolar disorder (BD) is a severe mental illness that can result from neurodevelopmental aberrations, particularly in familial BD, which may include causative genetic variants. In the present study, we derived cortical organoids from BD patients and healthy (control) individuals from a clinically dense family in the Indian population. Our data reveal that the patient organoids show neurodevelopmental anomalies, including organisational, proliferation and migration defects. The BD organoids show a reduction in both the number of neuroepithelial buds/cortical rosettes and the ventricular zone size. Additionally, patient organoids show a lower number of SOX2-positive and EdU-positive cycling progenitors, suggesting a progenitor proliferation defect. Further, the patient neurons show abnormal positioning in the ventricular/intermediate zone of the neuroepithelial bud. Transcriptomic analysis of control and patient organoids supports our cellular topology data and reveals dysregulation of genes crucial for progenitor proliferation and neuronal migration. Lastly, time-lapse imaging of neural stem cells in 2D in vitro cultures reveals abnormal cellular migration in BD samples. Overall, our study pinpoints a cellular and molecular deficit in BD patient-derived organoids and neural stem cell cultures.

Peripheral signature of altered synaptic integrity in young onset cannabis use disorder: A proteomic study of circulating extracellular vesicles.

BACKGROUND: Rates of Cannabis Use Disorder (CUD) are highest amongst young adults. Paucity of brain tissue samples limits the ability to examine the molecular basis of cannabis related neuropathology. Proteomic studies of neuron-derived extracellular vesicles (NDEs) isolated from the biofluids may reveal markers of neuropathology in CUD. METHODS: NDEs were extracted using ExoSORT, an immunoaffinity method to enrich NDEs from plasma samples from patients with young onset CUD and matched controls. Differential proteomic profiles were explored with Label Free Quantification (LFQ) mass spectrometry. Selected proteins were validated using orthogonal methods. RESULTS: A total of 231 (±10) proteins were identified in NDE preparations from CUD and controls of which 28 were differentially abundant between groups. The difference in abundance of properdin (CFP gene) was statistically significant. SHANK1 (SHANK1 gene), an adapter protein at the post-synaptic density, was nominally depleted in the CUD NDE preparations. CONCLUSION: In this pilot study, we noted a decrease in SHANK1 protein, involved in the structural and functional integrity of glutamatergic post-synapse, a potential peripheral signature of CUD neuropathology. The study shows that LFQ mass spectrometry proteomic analysis of NDEs derived from plasma may yield important insights into the synaptic pathology associated with CUD.

Delta-9-Tetrahydrocannabinol, Cannabidiol, and Acute Psychotomimetic States: A Balancing Act of the Principal Phyto-Cannabinoids on Human Brain and Behavior.

Background: THC and CBD are the principal phyto-cannabinoids in the cannabis plant. The differential and possibly antagonistic effects of these compounds on specific brain and behavioral responses, and the mechanisms underlying their effects have generated extensive interest in pre-clinical and clinical neuroscience investigations. Methods: In this double-blind randomized placebo-controlled counterbalanced Human Laboratory Study, we examined the effects of three different dose ratios of CBD:THC (1:1, 2:1, and 3:1) on "neural noise," an electrophysiological biomarker of psychosis known to be sensitive to cannabinoids as well as subjective and psychotomimetic effects. Healthy volunteers (n=28, 12 women) with at least one prior exposure to cannabis participated in the study. Outcomes: The lowest CBD (2.5 mg):THC (0.035 mg/kg) ratio (1:1) resulted in maximal attenuation of both THC-induced psychotomimetic effects (Positive and Negative Syndrome Scale [PANSS] positive: Anova Type Statistic [ATS]=7.83, pcorrected=0.015) and neural noise (ATS=8.83, pcorrected=0.009). Further addition of CBD did not reduce the subjective experience of THC-induced "high" (p>0.05 for all CBD doses). Interpretation: These novel results demonstrate that CBD attenuates specific THC-induced subjective and objective effects relevant to psychosis in a dose/ratio-dependent manner. Given the increasing global trend of cannabis liberalization and application for medical indications, these results assume considerable significance given the potential dose-related interactions of these key phyto-cannabinoids. Trial registration: The trial was registered in clinicaltrials.gov ID: NCT01180374.

Tracking momentary fluctuations in human attention with a cognitive brain-machine interface.

Selective attention produces systematic effects on neural states. It is unclear whether, conversely, momentary fluctuations in neural states have behavioral significance for attention. We investigated this question in the human brain with a cognitive brain-machine interface (cBMI) for tracking electrophysiological steady-state visually evoked potentials (SSVEPs) in real-time. Discrimination accuracy (d') was significantly higher when target stimuli were triggered at high, versus low, SSVEP power states. Target and distractor SSVEP power was uncorrelated across the hemifields, and target d' was unaffected by distractor SSVEP power states. Next, we trained participants on an auditory neurofeedback paradigm to generate biased, cross-hemispheric competitive interactions between target and distractor SSVEPs. The strongest behavioral effects emerged when competitive SSVEP dynamics unfolded at a timescale corresponding to the deployment of endogenous attention. In sum, SSVEP power dynamics provide a reliable readout of attentional state, a result with critical implications for tracking and training human attention.

Whole exome sequencing in dense families suggests genetic pleiotropy amongst Mendelian and complex neuropsychiatric syndromes.

Whole Exome Sequencing (WES) studies provide important insights into the genetic architecture of serious mental illness (SMI). Genes that are central to the shared biology of SMIs may be identified by WES in families with multiple affected individuals with diverse SMI (F-SMI). We performed WES in 220 individuals from 75 F-SMI families and 60 unrelated controls. Within pedigree prioritization employed criteria of rarity, functional consequence, and sharing by ≥ 3 affected members. Across the sample, gene and gene-set-wide case-control association analysis was performed with Sequence Kernel Association Test (SKAT). In 14/16 families with ≥ 3 sequenced affected individuals, we identified a total of 78 rare predicted deleterious variants in 78 unique genes shared by ≥ 3 members with SMI. Twenty (25%) genes were implicated in monogenic CNS syndromes in OMIM (OMIM-CNS), a fraction that is a significant overrepresentation (Fisher's Exact test OR = 2.47, p = 0.001). In gene-set SKAT, statistically significant association was noted for OMIM-CNS gene-set (SKAT-p = 0.005) but not the synaptic gene-set (SKAT-p = 0.17). In this WES study in F-SMI, we identify private, rare, protein altering variants in genes previously implicated in Mendelian neuropsychiatric syndromes; suggesting pleiotropic influences in neurodevelopment between complex and Mendelian syndromes.

Feasibility, Acceptability, and Performance of a Continuous Temperature Monitor in Older Adults and Staff in Congregate-Living Facilities.

OBJECTIVES: Residents of congregate-living facilities are susceptible to disability and mortality from infection given the presence of advanced age, multimorbidity, and frailty-as demonstrated in the recent COVID pandemic. This study assessed the feasibility, acceptability, and applicability of a continuous temperature monitoring device in a congregate-living facility with residents of independent living, assisted living, and their care-providing staff. We hypothesized that a wearable device compared with daily manual temperature assessment would be well tolerated and more effective at detecting temperature variances than current standard of care body temperature assessment. DESIGN: Feasibility study. SETTING AND PARTICIPANTS: Residents of assisted and independent living and staff of a retirement community. METHODS: Thirty-five participants, including residents in assisted- and independent-living facilities (25) and staff (10) were enrolled in a 90-day feasibility study and wore a continuous temperature sensor from March to July 2021. Primary outcomes included study completion, ability to reapply the sensor, temperature data acquisition, and data availability from the sensors. A secondary analysis of the temperature data involved comparing the method of obtaining temperature using the continuous monitoring device against standard of care using traditional manual thermometers. RESULTS: Overall, 91.3% of residents, who were in the study during the first reapplication, were able to apply the device without assistance (21 of 23), and 80% of resident participants completed the study (20 of 25). For staff participants, completion rates and reapplication rates were 100%. Data acquisition rates from the continuous temperature devices were much higher than manual temperatures. Four episodes of fever were detected by the devices; manual temperature checks did not identify these events. CONCLUSIONS AND IMPLICATIONS: Continuous temperature monitoring in an older adult population and the staff in congregate-living facilities is feasible and acceptable. This approach identified fever undetected by current standard of care indicating the capability of this device for earlier detection of fevers.

Consensus paper of the WFSBP task force on cannabis, cannabinoids and psychosis.

OBJECTIVES: The liberalisation of cannabis laws, the increasing availability and potency of cannabis has renewed concern about the risk of psychosis with cannabis. METHODS: The objective of the WFSBP task force was to review the literature about this relationship. RESULTS: Converging lines of evidence suggest that exposure to cannabis increases the risk for psychoses ranging from transient psychotic states to chronic recurrent psychosis. The greater the dose, and the earlier the age of exposure, the greater the risk. For some psychosis outcomes, the evidence supports some of the criteria of causality. However, alternate explanations including reverse causality and confounders cannot be conclusively excluded. Furthermore, cannabis is neither necessary nor sufficient to cause psychosis. More likely it is one of the multiple causal components. In those with established psychosis, cannabis has a negative impact on the course and expression of the illness. Emerging evidence also suggests alterations in the endocannabinoid system in psychotic disorders. CONCLUSIONS: Given that exposure to cannabis and cannabinoids is modifiable, delaying or eliminating exposure to cannabis or cannabinoids, could potentially impact the rates of psychosis related to cannabis, especially in those who are at high risk for developing the disorder.

Analysis of circulating exosomes reveals a peripheral signature of astrocytic pathology in schizophrenia.

OBJECTIVES: Extracellular vesicles, including exosomes, cross the blood brain barrier with their contents intact and can be assayed peripherally. Circulating exosomes have been studied in other neurodegenerative disorders, but there is scarce data in schizophrenia. This study aimed to examine neuropathology-relevant protein biomarkers in circulating plasma-derived exosomes from patients with schizophrenia and age- and sex-matched healthy controls. METHODS: Nanoparticle tracking analysis was used to determine the size and concentration of exosomes. Exosomal membrane marker (CD9) and specific target cargo protein (glial fibrillary acid protein[GFAP], synaptophysin, and α-II-Spectrin) immunopositivity was examined using Western blot analyses with band intensity quantified. Methods were consistent with the 'Minimal information for studies of extracellular vesicles 2018' (MISEV2018) guidelines. RESULTS: Exosomal GFAP concentration was significantly higher and α-II-Spectrin expression significantly lower in plasma obtained from schizophrenia patients. No group differences were observed between in plasma exosomal concentration and size or in CD9, calnexin, or synaptophysin levels. CONCLUSIONS: Our results demonstrate a differential pattern of exosomal protein expression in schizophrenia compared to matched healthy controls, consistent with the hypothesised astroglial pathology in this disorder. These results warrant further examination of circulating exosomes as vehicles of novel peripheral biomarkers of disease in schizophrenia and other neuropsychiatric disorders.

A Novel Wearable Device for Continuous Temperature Monitoring & Fever Detection.

Objective: Continuous temperature monitoring in high-risk patients can enable healthcare providers to remotely track patients' temperatures, promptly detect fevers and timely intervene to improve clinical outcomes. We evaluated if a novel wearable, continuous temperature monitor (Verily Patch) can reliably estimate body temperature and early detect fevers in an outpatient setting in patients at a high risk of febrile neutropenia (FN) who recently underwent chemotherapy and autologous stem cell transplantation (ASCT). Methods: 86 patients at a high risk for FN were prospectively enrolled at Mayo Clinic, MN. Patients wore the device in their axilla region for 7 days post ASCT and recorded self-measured oral temperatures every 3 hours. Patients were also followed using clinical standard-of-care procedures with daily oral temperature assessment. The clinic- and patient-assessed oral temperatures were used to develop and evaluate Verily Patch's body temperature and early fever detection algorithms using a K-fold cross-validation approach. Results: The Verily Patch reliably measured body temperatures with an error of 0.35 ± 0.88°F in comparison to clinic- and patient-assessed oral temperatures. The sensitivity and specificity of the patch in detecting clinic-assessed fever episodes was 90.2% and 87.8%. The patch detected 14.3 times the number of clinic-assessed fever episodes with a median lead time of 4.3 hours. Conclusion: Patient self-monitoring of temperature and fever incidents suffers from low accuracy and is impractical for extended periods of time. Continuous temperature monitoring by a wearable device (such as Verily Patch) has the potential to overcome these challenges resulting in better patient clinical outcomes and more cost-effective care.

Preliminary in vivo evidence of lower hippocampal synaptic density in cannabis use disorder.

Cannabis is one of the most commonly and widely used psychoactive drugs. The rates of cannabis misuse have been increasing. Therefore, understanding the effects of cannabis use on the brain is important. Adolescent and adult rodents exposed to repeated administration of cannabinoids show persistent microstructural changes in the hippocampus both pre- and post-synaptically. Whether similar alterations exist in human cannabis users, has not yet been demonstrated in vivo. Positron emission tomography (PET) and [11C]UCB-J, a radioligand for the synaptic vesicle glycoprotein 2A (SV2A), were used to study hippocampal synaptic integrity in vivo in an equal number (n = 12) of subjects with DSM-5 cannabis use disorder (CUD) and matched healthy controls (HC). Arterial sampling was used to measure plasma input function. [11C]UCB-J binding potential (BPND) was estimated using a one-tissue (1T) compartment model with centrum semiovale as the reference region. Hippocampal function was assessed using a verbal memory task. Relative to HCs, CUDs showed significantly lower [11C]UCB-J BPND in the hippocampus (~10%, p = 0.008, effect size 1.2) and also performed worse on the verbal memory task. These group differences in hippocampal BPND persisted after correction for volume differences (p = 0.013), and correction for both age and volume (p = 0.03). We demonstrate, for the first time, in vivo evidence of lower hippocampal synaptic density in cannabis use disorder. These results are consistent with the microstructural findings from experimental studies with cannabinoids in animals, and studies of hippocampal macrostructure in human with CUD. Whether the lower hippocampal synaptic density resolves with abstinence warrants further study.

Adverse childhood experiences in families with multiple members diagnosed to have psychiatric illnesses.

OBJECTIVE: Adverse childhood experiences are linked to the development of a number of psychiatric illnesses in adulthood. Our study examined the pattern of adverse childhood experiences and their relation to the age of onset of major psychiatric conditions in individuals from families that had ⩾2 first-degree relatives with major psychiatric conditions (multiplex families), identified as part of an ongoing longitudinal study. METHODS: Our sample consisted of 509 individuals from 215 families. Of these, 268 were affected, i.e., diagnosed with bipolar disorder (n = 61), obsessive-compulsive disorder (n = 58), schizophrenia (n = 52), substance dependence (n = 59) or co-occurring diagnoses (n = 38), while 241 were at-risk first-degree relatives who were either unaffected (n = 210) or had other depressive or anxiety disorders (n = 31). All individuals were evaluated using the Adverse Childhood Experiences - International Questionnaire and total adverse childhood experiences exposure and severity scores were calculated. RESULTS: It was seen that affected males, as a group, had the greatest adverse childhood experiences exposure and severity scores in our sample. A Cox mixed effects model fit by gender revealed that a higher total adverse childhood experiences severity score was associated with significantly increased risk for an earlier age of onset of psychiatric diagnoses in males. A similar model that evaluated the interaction of diagnosis revealed an earlier age of onset in obsessive-compulsive disorder and substance dependence, but not in schizophrenia and bipolar disorder. CONCLUSION: Our study indicates that adverse childhood experiences were associated with an earlier onset of major psychiatric conditions in men and individuals diagnosed with obsessive-compulsive disorder and substance dependence. Ongoing longitudinal assessments in first-degree relatives from these families are expected to identify mechanisms underlying this relationship.

Psychosis-Relevant Effects of Intravenous Delta-9-Tetrahydrocannabinol: A Mega Analysis of Individual Participant-Data from Human Laboratory Studies.

INTRODUCTION: There is increasing interest in the relationship between cannabinoids and psychosis. While individual human laboratory studies have been critical in demonstrating that cannabinoids (e.g., delta-9-tetrahydrocannabinol [THC]) can induce acute transient psychosis-like effects in healthy human volunteers, combining data from multiple studies offers a fine-grained view of these effects. METHODS: THC-induced psychosis-relevant effects were examined using a data repository of 10 double-blind, randomized, placebo-controlled, crossover studies with 400 i.v. THC infusions in healthy human volunteers. The Positive and Negative Syndrome scale was used to measure psychotomimetic effects. The profile of symptoms, frequency of a response, its relationship to THC dose and substance use, latent structure in Positive and Negative Syndrome scale response, and the relationships between psychotomimetic and perceptual alteration symptoms were evaluated. RESULTS: Clinically meaningful increases in positive symptoms were noted in 44.75% infusions; conceptual disorganization, hallucinations, blunted affect, somatic concern, motor retardation, and poor attention were the items most frequently altered by THC. The increase in Positive and Negative Syndrome scale positive symptoms was positively associated with THC dose (beta = 11.13, SE = 4.94, Wald χ 2 = 19.88, P < .001) and negatively associated with frequent cannabis use (beta = -0.575, SE = 0.14, Wald χ 2 = 18.13, P < .001). Furthermore, positive symptoms were strongly correlated with Clinician Administered Dissociative States Scale perceptual alterations score (rs = 0.514, P < .001). CONCLUSION: Intravenous administration of THC consistently induces psychotomimetic effects that include symptoms across Positive and Negative Syndrome scale domains. Moreover, healthy individuals who frequently use cannabis have a blunted psychotomimetic response.

Psychiatric symptoms caused by cannabis constituents: a systematic review and meta-analysis.

BACKGROUND: Approximately 188 million people use cannabis yearly worldwide, and it has recently been legalised in 11 US states, Canada, and Uruguay for recreational use. The potential for increased cannabis use highlights the need to better understand its risks, including the acute induction of psychotic and other psychiatric symptoms. We aimed to investigate the effect of the cannabis constituent Δ9-tetrahydrocannabinol (THC) alone and in combination with cannabidiol (CBD) compared with placebo on psychiatric symptoms in healthy people. METHODS: In this systematic review and meta-analysis, we searched MEDLINE, Embase, and PsycINFO for studies published in English between database inception and May 21, 2019, with a within-person, crossover design. Inclusion criteria were studies reporting symptoms using psychiatric scales (the Brief Psychiatric Rating Scale [BPRS] and the Positive and Negative Syndrome Scale [PANSS]) following the acute administration of intravenous, oral, or nasal THC, CBD, and placebo in healthy participants, and presenting data that allowed calculation of standardised mean change (SMC) scores for positive (including delusions and hallucinations), negative (such as blunted affect and amotivation), and general (including depression and anxiety) symptoms. We did a random-effects meta-analysis to assess the main outcomes of the effect sizes for total, positive, and negative PANSS and BPRS scores measured in healthy participants following THC administration versus placebo. Because the number of studies to do a meta-analysis on CBD's moderating effects was insufficient, this outcome was only systematically reviewed. This study is registered with PROSPERO, CRD42019136674. FINDINGS: 15 eligible studies involving the acute administration of THC and four studies on CBD plus THC administration were identified. Compared with placebo, THC significantly increased total symptom severity with a large effect size (assessed in nine studies, with ten independent samples, involving 196 participants: SMC 1·10 [95% CI 0·92-1·28], p<0·0001); positive symptom severity (assessed in 14 studies, with 15 independent samples, involving 324 participants: SMC 0·91 [95% CI 0·68-1·14], p<0·0001); and negative symptom severity with a large effect size (assessed in 12 studies, with 13 independent samples, involving 267 participants: SMC 0·78 [95% CI 0·59-0·97], p<0·0001). In the systematic review, of the four studies evaluating CBD's effects on THC-induced symptoms, only one identified a significant reduction in symptoms. INTERPRETATION: A single THC administration induces psychotic, negative, and other psychiatric symptoms with large effect sizes. There is no consistent evidence that CBD induces symptoms or moderates the effects of THC. These findings highlight the potential risks associated with the use of cannabis and other cannabinoids that contain THC for recreational or therapeutic purposes. FUNDING: UK Medical Research Council, Maudsley Charity, Brain and Behavior Research Foundation, Wellcome Trust, and the UK National Institute for Health Research.

Single-cell Transcriptome Mapping Identifies Common and Cell-type Specific Genes Affected by Acute Delta9-tetrahydrocannabinol in Humans.

Delta-9-tetrahydrocannabinol (THC) is known to modulate immune response in peripheral blood cells. The mechanisms of THC's effects on gene expression in human immune cells remains poorly understood. Combining a within-subject design with single cell transcriptome mapping, we report that THC acutely alters gene expression in 15,973 blood cells. We identified 294 transcriptome-wide significant genes among eight cell types including 69 common genes and 225 cell-type-specific genes affected by THC administration, including those genes involving in immune response, cytokine production, cell proliferation and apoptosis. We revealed distinct transcriptomic sub-clusters affected by THC in major immune cell types where THC perturbed cell-type-specific intracellular gene expression correlations. Gene set enrichment analysis further supports the findings of THC's common and cell-type-specific effects on immune response and cell toxicity. This comprehensive single-cell transcriptomic profiling provides important insights into THC's acute effects on immune function that may have important medical implications.

Association of SLC1A1 gene polymorphism with obsessive compulsive disorder in a sample from southern India.

The glutamate transporter gene SLC1A1 has been shown to have an association with obsessive-compulsive disorder (OCD), and serotonin reuptake inhibitor (SRI) treatment response. One polymorphism (rs3056) in SLC1A1 has been associated with altered brain volumes in OCD. We investigated the association of this polymorphism with OCD and its relationship with various clinical parameters, including age of onset, disease severity, insight, factor analyzed symptom dimensions of OCD, and SRI treatment response. Three hundred seventy seven OCD patients (DSM-IV) aged between 18 to 60 years were recruited from a specialty OCD clinic. To study the association with SRI treatment response, we analyzed full responders (≥35% reduction in the Yale Brown Obsessive Compulsive Scale [YBOCS] and the Clinical Global Impression-Improvement [CGI-I] score of 1 or 2) to any SRI (n = 187) and nonresponders (<25% reduction in the YBOCS and the CGI-I score >4) to adequate trials of at least two SRIs for a duration of 12 weeks (n = 91). Healthy controls (n = 333) were recruited and evaluated using the Mini-International Neuropsychiatric Interview-Plus (MINI-Plus). All subjects were from southern India, and were genotyped for the SLC1A1 polymorphism (rs3056). Genotype frequencies did not deviate significantly from the Hardy-Weinberg equilibrium. Case-control association analysis revealed that the "GG" genotype was significantly more frequent in OCD cases than the controls (p = .04). No association was found with the age of onset, symptom severity, insight, and symptom dimensions. No significant association was found between genotype/allele frequencies with treatment response. To conclude, although there was a significant association between the SLC1A1 rs3056 polymorphism and OCD, there were no significant associations with other clinical parameters or treatment response. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Characterizing psychosis-relevant phenomena and cognitive function in a unique population with isolated, chronic and very heavy cannabis exposure.

BACKGROUND: The literature on psychosis-relevant outcomes in cannabis users does not adequately address the confounding effects of other substance use/misuse and psychiatric disorders. METHODS: We studied a unique population for whom cannabis use is central and necessary to their way of life. They are forbidden from using other substances, including tobacco and alcohol. Their use of cannabis is heavy, chronic, and begins early. The cases were compared with matched controls who did not use cannabis, alcohol, or drugs. The controls were from the same location and shared similar beliefs and lifestyle, except for cannabis use. Attenuated psychosis-relevant phenomena were assessed with the Schizotypal Personality Questionnaire (SPQ) and cognitive functioning with a culture-neutral computerized cognitive battery. RESULTS: Fifteen cases and 12 matched controls were studied. The cases averaged >30 000 lifetime cannabis exposures. Relative to controls, the cases had significantly higher mean (s.d.) SPQ scores 24 (14.32) v. 13 (8.92), p = 0.031; and poorer cognitive performance, reflected by a lower mean (s.d.) composite cognitive score -0.23 (0.32) v. +0.28 (0.52), p = 0.03. Moderate to large effect sizes were noted for differences in tests of attention, psychomotor speed, working memory, cognitive flexibility, visuo-spatial processing, and verbal memory. A subsample of cases had higher SPQ scores and worse cognitive performance than their siblings not using cannabis. CONCLUSION: Heavy, chronic, and early cannabis use that is not confounded by other drug use is associated with psychosis-relevant phenomena and cognitive deficits. The findings are relevant to the evolving attitudes and laws about cannabis.

The 2019 Schizophrenia International Research Society Conference, 10-14 April, Orlando, Florida: A summary of topics and trends.

The Schizophrenia International Research Society (SIRS) recently held its first North American congress, which took place in Orlando, Florida from 10-14 April 2019. The overall theme of this year's congress was United in Progress - with the aim of cultivating a collaborative effort towards advancing the field of schizophrenia research. Student travel awardees provided reports of the oral sessions and concurrent symposia that took place during the congress. A collection of these reports is summarized and presented below and highlights the main themes and topics that emerged during the congress. In summary, the congress covered a broad range of topics relevant to the field of psychiatry today.