Incidence Of Schizophrenia Research Articles

The Role of Systemic Inflammation in Psychiatric Disorders Development in Children: Literature Review

There has been significant increase in mental disorders prevalence in pediatric population around the world. Increasing incidence of autism, intellectual incapacity, hyperkinetic disorders, and schizophrenia gives causes for specific concern. Clarifying mental disorders’ etiology and pathogenesis is the priority of researchers. The role of systemic inflammation in psychiatric disorders development currently remains the least studied. However, it can already be stated that generalized peripheral inflammation is the important factor associated with the development of mental disorders both in adults and children. This review presents latest data, as well as an authors’ assessment of systemic inflammation role in the most common mental disorders development in children. Comparative analysis of acute and chronic systemic inflammation manifestations has been performed. The major pathogenetic mechanisms of “systemic damage” in mental disorders have been identified.

The Impact of Childhood Experiences on the Incidence of Schizophrenia

The impact of childhood experiences on the development of schizophrenia has received considerable attention in recent studies. This study aimed to explore the relationship between adverse childhood experiences (ACEs) and the incidence of schizophrenia. A mixed methods approach was employed, analyzing data from longitudinal studies, clinical assessments, and patient interviews to investigate this relationship. The findings indicate that individuals who experienced high levels of ACEs are at significantly higher risk of developing schizophrenia compared to those with fewer or no ACEs. These results highlight the importance of early intervention and prevention strategies to mitigate the negative impact of childhood adversity on long-term mental health. This research underscores the need for comprehensive strategies that address the root causes of ACEs and provide support for at-risk populations, ultimately aiming to reduce the incidence of schizophrenia linked to childhood adversity.

Air pollutants, genetic susceptibility, and incident schizophrenia in later life: A prospective study in the UK Biobank

ObjectiveAir pollution has been linked to multiple psychiatric disorders, but little is known on its long-term association with schizophrenia. The interaction between air pollution and genetic susceptibility on incident schizophrenia has never been reported. We aimed to explore the associations between long-term air pollution exposure and late-onset schizophrenia and evaluate whether genetic susceptibility could modify the association. MethodsThis population-based prospective cohort study included 437,802 middle-aged and elderly individuals free of schizophrenia at baseline in the UK Biobank. Land use regression models were applied in the estimation of the annual average concentrations of nitrogen dioxide (NO2), nitrogen oxides (NOx), fine particulate matter (PM2.5), and inhalable particulate matter (PM10) at residence. The associations between air pollutants and schizophrenia were evaluated by using Cox proportional hazard models. A polygenic risk score of schizophrenia was constructed for exploring potential interaction of air pollutants with genetic susceptibility. ResultsAn interquartile range increase in PM2.5, PM10, NO2, and NOx was associated with the hazard ratios (HR) for incident schizophrenia at 1.19, 1.16, 1.22, and 1.09, respectively. The exposure-response curves for the association of air pollution with incident schizophrenia were approximately linear. There are additive interactions of air pollution score (APS), PM10, NO2, and NOx with genetic risk. Specifically, compared with participants with low genetic susceptibility and low APS, the HR was 3.23 for individuals with high genetic risk and high APS, among which 0.49 excess risk could be attributed to the additive interaction, accounting for 15 % of the schizophrenia risk. ConclusionThis large-scale, prospective cohort study conveys the first-hand evidence that long-term air pollution exposure could elevate schizophrenia incidence in later life, especially for individuals with higher genetic risks. The findings highlight the importance of improving air quality for preventing the late-onset schizophrenia in an aging era, especially among those with high genetic risks.

Toxoplasma gondii infection positively associated with schizophrenia: Evidences from UK Biobank cohort and case-controlled studies

Toxoplasma gondii (T. gondii) is an opportunistic pathogen affecting about 1/3 of world population. While often asymptomatic in immunocompetent individuals, it can lead to severe toxoplasmosis in immunocompromised patients. Recent research has unveiled a potential link between T. gondii infection and neuropsychiatric diseases. We implemented both a cohort study and a case control study to further identify this association. In the cohort study, we analyzed data from the UK Biobank database, which included 8814 individuals tested for T. gondii SAG1 antibodies and free of neuropsychiatric disorders at baseline. Among them, 22.52% (n = 1985) tested positive for SAG1 antibody. Over an average follow-up period of 12.26 years, Cox proportional hazards models and logistic regression analysis revealed a significant association between the SAG1 seropositivity at baseline and the incidence of schizophrenia (HR: 5.89; 95% CI: 1.69–20.53). In our case-control study, 239 patients diagnosed with schizophrenia and 455 healthy individuals were involved. Using the modified agglutination test (MAT) to detect T. gondii antibodies, logistic regression analysis showed a higher prevalence of T. gondii infection among schizophrenia patients (10.04%) compared to healthy controls (3.74%). T. gondii infection emerged as a significant risk factor for schizophrenia (OR: 3.33; 95% CI: 1.68–6.61). However, our investigations did not reveal a robust association between T. gondii infection and other neuropsychiatric conditions, including Alzheimer's disease, dementia, anxiety, depression, neurodegenerative disorders, and peripheral neurological disorders such as neurological and plexus disorders.

Relationship between methylation pattern of the SYN2 gene and schizophrenia

Abstract Objectives Schizophrenia is a neuropsychiatric disease, and its etiology is not exactly understood. DNA methylation is an important phenomenon that affects the rise of abnormal phenotypes in many cases. Investigation of the association between DNA methylation and schizophrenia is crucial for elucidating the basis of schizophrenia. Previous association studies confirm that the SYN2 gene is a strong candidate gene for schizophrenia. In the current study, the relationship between the methylation status of the SYN2 gene and schizophrenia was investigated. The aim is to obtain crucial results for illuminating the effects of the SYN2 methylation changes in the etiology of schizophrenia. Methods In light of this scientific information, we investigated the methylation status of three different CpG regions in the promoter of the SYN2 gene and compared them in healthy controls and schizophrenia patients. Thirty-three healthy controls and 36 schizophrenia patients were included in this study. Sequencing was performed using the pyrosequencing method to reveal the methylation pattern. Results As a result of the statistical analysis, it was confirmed that there is a significant relationship between the methylation pattern of the SYN2 gene and schizophrenia. Schizophrenia patients showed more methylation in position 2 and position 3. Additionally, the average methylation ratio is increased in schizophrenia patients. Conclusions We find an association between the DNA methylation pattern of the SYN2 gene and schizophrenia. These results can help to the understanding of the etiology of schizophrenia. Except for these, DNA methylation changes in the SYN2 gene in people who live in urban and rural areas can be one of the reasons for the different incidences of schizophrenia in these regions.

High-risk state for psychosis: psychometric screening tools

The purpose of this article is to highlight current ideas available in the world literature about high-risk state for psychosis as a promising diagnostic stage for identification risk groups for the development of schizophrenia in the near future, as well as to allocate and characterize the tools for screening the highrisk state for psychosis.Identification and timely correction of risk factors is a relevant method for reducing the incidence of schizophrenia and improving the prognosis of the disease.As a result of the literature data analysis with a summary of the available results of original researches, systematic reviews and meta-analyses the data about currently available approaches to unified standardized diagnostics of high-risk state for psychosis are presented, and their comparative characteristic is carried out.According to the review of publications, none of the currently available tools fully covers all contemporary diagnostic approaches, and therefore, in order to achieve an optimal result in identifying a state of high risk of psychosis, the combined use of various tools seems to be the most reliable. In addition, the further development of available screening tools and their validation in the Russian population remains relevant.

Novel missense variants in brain morphogenic genes associated with depression and schizophrenia.

Impaired function of brain morphogenic genes is considered one of the predisposing factors for the manifestation of psychiatric and cognitive disorders, such as paranoid schizophrenia (SCZ) and major depressive disorder (MDD). Identification of such genes (genes of neurotrophic factors and guidance molecules among them) and their deleterious genetic variants serves as a key to diagnosis, prevention, and possibly treatment of such disorders. In this study, we have examined the prevalence of genomic variants in brain morphogenic genes in individuals with SCZ and MDD within a Russian population. We have performed whole-exome sequencing of 21 DNA samples: 11 from individuals with SCZ and 10 with MDD, followed by ARMS (Amplification-Refractory Mutation System) based screening of detected single nucleotide variants (SNVs) in larger groups: 102 for individuals with SCZ, 79 for those with MDD and 103 for healthy donors. Whole-exome sequencing has revealed 226 missense mutations in 79 genes (out of 140 studied), some of which occur in patients with psychiatric disorders significantly more frequently than in healthy donors. We have identified previously undescribed genomic variants in brain morphogenic genes: CDH2 (rs1944294-T and rs17445840-T), DCHS2 (rs11935573-G and rs12500437-G/T) and CDH23 (rs1227051-G/A), significantly associated with the incidence of SCZ and MDD in the Russian population. For some SNVs (rs6265-T, rs1944294-T, rs11935573-G, rs4760-G) sex-biased differences in their prevalence between SCZ/MDD patients and healthy donors was detected. However, the functional significance of the SNVs identified has still to be confirmed in cellular and animal models. Once it is fulfilled, these SNVs have the potential to complement the diagnostic toolbox for assessing susceptibility to mental disorders. The data obtained indirectly confirm the importance of adequate brain structure formation for its correct functioning and preservation of mental health.

Impact of COVID-19 on the development of major mental disorders in patients visiting a university hospital: a retrospective observational study.

This study aimed to investigate the impact of coronavirus disease 2019 (COVID-19) on the development of major mental disorders in patients visiting a university hospital. The study participants were patients with COVID-19 (n=5,006) and those without COVID-19 (n=367,162) registered in the database of Keimyung University Dongsan Hospital and standardized with the Observational Medical Outcomes Partnership Common Data Model. Data on major mental disorders that developed in both groups over the 5-year follow-up period were extracted using the FeederNet computer program. A multivariate Cox proportional hazards model was used to estimate the hazard ratio (HR) and 95% confidence interval (CI) for the incidence of major mental disorders. The incidences of dementia and sleep, anxiety, and depressive disorders were significantly higher in the COVID-19 group than in the control group. The incidence rates per 1,000 patient-years in the COVID-19 group vs. the control group were 12.71 vs. 3.76 for dementia, 17.42 vs. 7.91 for sleep disorders, 6.15 vs. 3.41 for anxiety disorders, and 8.30 vs. 5.78 for depressive disorders. There was no significant difference in the incidence of schizophrenia or bipolar disorder between the two groups. COVID-19 infection increased the risk of mental disorders in the following order: dementia (HR, 3.49; 95% CI, 2.45-4.98), sleep disorders (HR, 2.27; 95% CI, 1.76-2.91), anxiety disorders (HR, 1.90; 95% CI, 1.25-2.84), and depressive disorders (HR, 1.54; 95% CI, 1.09-2.15). This study showed that the major mental disorders associated with COVID-19 were dementia and sleep, anxiety, and depressive disorders.

Эпидемиология шизофрении: смена парадигмы?

The article analyzes the results of meta-analyses of epidemiological studies on the occurrence of schizophrenia (incidence and prevalence), which revealed a dependence of the occurrence of schizophrenia on gender, season of birth, degree of urbanization, migration, climate severity, geographic latitude of the population sites and some other factors. The established various indicators of the occurrence of schizophrenia in some countries and regions are given, taking into account their geographical latitude; information about some peculiar features of the incidence of schizophrenia (increased incidence in second generation migrants compared to first-generation migrants, an increased risk of schizophrenia for those born in winter in the absence of any mental illness in family history and for those born in spring in the presence of schizophrenia in family history). The conflicting results from studies are also discussed, the possible explanations include different sample sizes, the use of heterogeneous occurrence rates (prevalence and incidence, age adjustment), a variety of diagnostic approaches, and the predominance of the use of medical records rather than personal examination by specialists.

The burden of depression, anxiety and schizophrenia among the older population in ageing and aged countries: an analysis of the Global Burden of Disease Study 2019

BackgroundDepression, anxiety and schizophrenia among older persons have become global public health challenges. However, the burden of these disorders in ageing and aged countries has not been analysed.AimsTo investigate the...

Incidence, prevalence, and mortality of schizophrenia from 2016 to 2020 in Shandong, China

The epidemiology of schizophrenia has been reported in many countries. However, due to the limitations of those studies, the findings cannot be generalized to other parts of the world, especially in China. In this study, the incidence, prevalence, and mortality of schizophrenia in Shandong, China were calculated using data from the National Severe Mental Disorder Registration System collected between 2016 and 2020 and census data from 2010 to 2020. The overall incidence decreased from 9.61 per 100,000 in 2016 to 4.40 per 100,000 in 2020, the aggregate prevalence was approximately 3.20 per 1000, and the overall mortality ranged from 6.17 per 100,000 to 7.71 per 100,000. The evidence from this study indicated that the incidence, prevalence, and mortality of schizophrenia were higher in rural areas than in urban areas. Females had higher incidence, prevalence, and mortality than males. This study provided epidemiological information on schizophrenia and opened avenues for future research.

Correlation of the Interferon Gamma Point +874 A/T Gene Polymorphism with the Occurrence of Schizophrenia

Schizophrenia is a mental illness characterized by delusions and hallucinations. Several investigations have revealed that the immune system and genetic factors have a role in the development of schizophrenia. Interferon gamma is one of the genes thought to have a role in the development of schizophrenia, and many studies have reported the involvement of interferon-gamma (IFN-γ) in neuropsychiatry. This study aims to determine the relationship between the Interferon-γ +874 A/T Gene Polymerphism with the incidence of Schizophrenia. A case control study was conducted at the hospital. Ernaldi Bahar Palembang for 3 months (February-April). There were 100 samples that met the inclusion criteria, of which 50 patients were cases and 50 respondents were healthy controls. Analysis of data using computerized data processing applications. The sampling method in this study is the matching sampling method. The results showed that the frequency of the A allele in the case group was 50 and in the control group was 69, while the frequency of the T allele in the case group was 50 and the control group was 31. The analysis of the results showed that the frequency of the T allele was higher in the schizophrenia group than the control group with value (p = 0.006), with an OR value of 2.226. There was a significant relationship between the case group and the control group. Individuals with the T allele have a 2,226 higher risk of developing schizophrenia than individuals with the A allele

Heredity of Schizophrenia in India: A 1928 debate

Shaw, a British psychiatrist working in India, observed that the incidence of Schizophrenia was higher among a community of Parsis as compared to other ethnic groups. He published his findings in two British journals. The paper drew responses from two other psychiatrists. The debate is examined in colonial context during which occurred and some implications for contemporary research.

The incidence of psychotic disorders in the Republic of Ireland: a systematic review.

Despite a substantial epidemiological literature on the incidence of psychotic disorders in Ireland, no systematic review has previously been undertaken. Such evidence can help inform understanding of need for psychosis care. We conducted a prospectively registered systematic review (PROSPERO: CRD42021245891) following PRISMA guidelines. We searched four databases (Medline, PsycInfo, Web of Science, Embase) for papers containing incidence data on non-organic psychotic disorders, in people 16-64 years, published between 1950 and 2021 in the general adult population. We conducted duplicate screening, risk of bias assessments, and extracted data to a standardised template. We undertook a narrative synthesis for each major diagnostic outcome. Random effects meta-analyses were conducted for comparisons with ≥5 incidence rates. Our search yielded 1975 non-duplicate citations, of which 23 met inclusion criteria, containing incidence data ascertained between 1974 and 2016 (median study quality: 5/8; interquartile range: 4-6). Incidence of all psychotic disorders (N = 4 studies) varied from 22.0 (95%CI: 17.3-28.0) in Dublin to 34.1 per 100,000 person-years (95%CI: 31.0-37.5) in Cavan and Monaghan. The pooled incidence of schizophrenia (N = 6 studies, N = 8 settings) was 20.0 per 100,000 person-years, though with imprecision around this estimate (95%CI: 10.6-37.5; I2: 97.6%). Higher rates of most outcomes were observed in men. There was consistent evidence of raised rates in more deprived and fragmented social environments, but no clear pattern by rural-urban status. Patterns of incidence of psychotic disorders in Ireland are broadly consistent with the wider literature from the Global North. Findings could help identify populations at higher risk of psychosis in Ireland.

Incidence, prevalence, and global burden of schizophrenia - data, with critical appraisal, from the Global Burden of Disease (GBD) 2019.

Schizophrenia substantially contributes to the burden of mental disorders. Schizophrenia's burden and epidemiological estimates in some countries have been published, but updated estimates of prevalence, incidence, and schizophrenia-related disability at the global level are lacking. Here, we present the data from and critically discuss the Global Burden of Diseases, Injuries, and Risk Factors Study data, focusing on temporal changes in schizophrenia's prevalence, incidence, and disability-adjusted life years (DALYs) globally. From 1990 to 2019, schizophrenia raw prevalence (14.2 to 23.6 million), incidence (941,000 to 1.3 million), and DALYs (9.1 to 15.1 million) increased by over 65%, 37%, and 65% respectively, while age-standardized estimates remained stable globally. In countries with high socio-demographic index (SDI), both prevalence and DALYs increased, while in those with low SDI, the age-standardized incidence decreased and DALYs remained stable. The male/female ratio of burden of schizophrenia has remained stable in the overall population over the past 30 years (i.e., M/F = 1.1), yet decreasing from younger to older age groups (raw prevalence in females higher than males after age 65, with males having earlier age of onset, and females longer life expectancy). Results of this worksuggest that schizophrenia's raw prevalence, incidence, and burden have been increasing since 1990. Age-adjusted estimates did not reduce. Schizophrenia detection in low SDI countries is suboptimal, and its prevention/treatment in high SDI countries should be improved, considering its increasing prevalence. Schizophrenia sex ratio inverts throughout the lifespan, suggesting different age of onset and survival by sex. However, prevalence and burden estimates for schizophrenia are probably underestimated. GBD does not account for mortality from schizophrenia (and other mental disorders, apart from anorexia nervosa).

Clinical and epidemiological aspects of schizotypal disorder in children and adolescents according to the Moscow psychiatric service

BACKGROUND: Given the significant increase in the number of children and adolescents diagnosed with schizotypal disorder and the simultaneous decrease in the incidence of schizophrenia in recent years, studying possible causes of the tendency and provision of psychiatric care to these patients is necessary. AIMS: To analyze the frequency of schizotypal disorder (F21) in children and adolescents and study the correspondence of diagnosis with the ICD-10 criteria and changes in accordance with disease dynamics to improve the continuity of psychiatric care. MATERIALS AND METHODS: This retrospective observational study analyzed data of patients who underwent examination and treatment at Sukhareva Scientific and Practical Center for Child and Adolescent Mental Health between 1999 and 2019, and the inpatient and outpatient records of the center and outpatient records of psychoneurological clinics at the place of patients residence were analyzed. RESULTS: The number of patients diagnosed with F21 schizotypal disorder increased along with the general increase in the number of patients (2812 people in 1999 and 5675 in 2019). They account for nearly half (48.3%) of the patients with diagnoses related to the schizophrenia spectrum (F2 schizophrenia and schizotypal and delusional disorders). Moreover, 71.2% of patients with F21 were diagnosed with F21.8 (schizotypal personality disorder). The number of patients diagnosed with schizophrenia decreased threefold, and the number of patients diagnosed with schizotypal disorder increased six-fold. Among those discharged with F21.8 diagnosis excluding rehospitalizations, 527 patients were selected for the clinical and follow-up study. After the exclusion of patients for various reasons, the patient cohort consisted of 139 patients who had been regularly followed up at psychoneurological clinics. The diagnoses with F2 code remained in 96% of 139 patients included in the cohort for the follow-up study, and only five patients had other disease codes. The diagnosis of schizotypal disorder (F21) persisted in 89 patients (64%). CONCLUSION: The decrease in schizophrenia diagnoses and the increase in the diagnosis of schizotypal disorders in children and adolescents, as revealed in the clinical and epidemiological study of ICD-10 use in 20 years, require further in-depth studies of the possible causes of this transformation. In light of the forthcoming adaptation of ICD-11, unified and clear criteria must be developed for schizotypal disorders, and a common understanding of their nosological affiliation is needed to develop more advanced approaches to diagnosis. The organization of psychiatric care provision must be improved to ensure the continuity of inpatient and outpatient care, including non-state institutions.

The incidence of schizophrenia in the context of growing up in urbanised vs. green areas – a narrative review

The neurodevelopmental theory of schizophrenia describes multiple risk factors of this serious mental disorder. These include genetic factors that generally have biological roots, as well as factors related to the upbringing in a specific environment during childhood and adolescence of a person who will develop schizophrenia in adulthood. The neurodevelopmental hypothesis also implies the existence of protective factors. The paper discusses selected environmental risk factors and protective factors of schizophrenia in the context of ecopsychiatry. Urbanicity has for decades been a factor indicated as one that increases the risk of schizophrenia. Contemporary research helps understand how growing up in an urban environment affects brain development, with a particular focus on grey matter volume changes in the dorsolateral prefrontal cortex and the perigenual anterior cingulate cortex. The impact of air pollution as a risk factor for schizophrenia is also the subject of discussions. Exposure to outdoor air pollutants containing particulate matter and ultrafine particulate matter, gases, organic compounds, and metals can lead to neurotoxicity and neuropathology. Air pollution can affect the brain through such mechanisms as inflammation and oxidative stress. On contrary, higher exposure to green spaces has been suggested to reduce the incidence of schizophrenia. Some research indicates a dose-response association between the level of exposure to green space in childhood and a lower risk of developing schizophrenia in the future. The presented review of selected publications indicates that exposure to a certain environment in childhood and adolescence modulates the risk of schizophrenia. Environments heavily transformed by human activity (urbanisation) and characterised by a high level of chemical contamination (toxins, air pollution, smog) are a risk factor for schizophrenia. Protective factors, on the other hand, include direct contact with the natural environment from childhood through adolescence to adulthood.

Association between cannabis use disorder and schizophrenia stronger in young males than in females.

Previous research suggests an increase in schizophrenia population attributable risk fraction (PARF) for cannabis use disorder (CUD). However, sex and age variations in CUD and schizophrenia suggest the importance of examining differences in PARFs in sex and age subgroups. We conducted a nationwide Danish register-based cohort study including all individuals aged 16-49 at some point during 1972-2021. CUD and schizophrenia status was obtained from the registers. Hazard ratios (HR), incidence risk ratios (IRR), and PARFs were estimated. Joinpoint analyses were applied to sex-specific PARFs. We examined 6 907 859 individuals with 45 327 cases of incident schizophrenia during follow-up across 129 521 260 person-years. The overall adjusted HR (aHR) for CUD on schizophrenia was slightly higher among males (aHR = 2.42, 95% CI 2.33-2.52) than females (aHR = 2.02, 95% CI 1.89-2.17); however, among 16-20-year-olds, the adjusted IRR (aIRR) for males was more than twice that for females (males: aIRR = 3.84, 95% CI 3.43-4.29; females: aIRR = 1.81, 95% CI 1.53-2.15). During 1972-2021, the annual average percentage change in PARFs for CUD in schizophrenia incidence was 4.8 among males (95% CI 4.3-5.3; p < 0.0001) and 3.2 among females (95% CI 2.5-3.8; p < 0.0001). In 2021, among males, PARF was 15%; among females, it was around 4%. Young males might be particularly susceptible to the effects of cannabis on schizophrenia. At a population level, assuming causality, one-fifth of cases of schizophrenia among young males might be prevented by averting CUD. Results highlight the importance of early detection and treatment of CUD and policy decisions regarding cannabis use and access, particularly for 16-25-year-olds.

Functional Connectivity Alterations of Within and Between Networks in Schizophrenia: A Retrospective Study

Introduction: Schizophrenia (SZ) is a chronic brain disorder characterized by diverse cognitive dysfunctions due to abnormal brain connectivity. Evaluating these connectivity alterations between and within such networks (intra- and inter-connectivity) may improve the understanding of disrupted information processing patterns in SZ patients. Methods: Resting-state fMRI analysis was performed on 24 SZ patients and 27 matched healthy controls. A functional connectivity matrix was constructed for each participant based on 129 gray matter regions. All regions were classified into eight distinct functional networks. Afterward, all functional connections were segregated into inter- and intra-network connections considering the eight networks. The Mean values of connectivity weights and nodal strength were examined for within- and between-network connections in SZ patients and healthy controls. Results: This analysis revealed that the within-network connections in the somatomotor (SM) network significantly reduced (P&lt;0.001) in SZ patients. Additionally, intra-network connections within the visual and the ventral attention (VA) networks were significantly lower (P&lt;0.01) in the SZ group. Moreover, disrupted intra-network connectivity was detected between the following network pairs: The visual-limbic, the somatomotor-limbic, the dorsal attention-limbic, and the ventral attention-dorsal attention system. Conclusion: The results showed an extensive reduction in functional connectivity strength for SZ patients, with a particularly significant decrease in intra-network connections when compared to the inter-networks. These findings can impact the understanding of the important dysregulated connections that are implicated in the incidence of schizophrenia.

Does a history of cannabis use influence onset and course of schizophrenia?

While evidence strongly supports a causal effect of cannabis on psychosis, it is less clear whether the symptom pattern, clinical course, and outcomes differ in cases of schizophrenia with and without a background of cannabis use. Analysis of medical records from a longitudinal follow-up of Swedish conscripts with data on cannabis use in adolescence and subsequent incidence of schizophrenia. One hundred sixty patients with schizophrenia were assessed using the OPCRIT protocol. Cases were validated for diagnosis schizophrenia according to OPCRIT. Patients with a cannabis history (n = 32), compared to those without (n = 128), had an earlier age at onset, a higher number of hospital admissions and a higher total number of hospital days. There was no significant difference in type of onset and clinical symptom profiles between the groups. Our findings indicate that the disease burden of schizophrenia is greater in individuals who use cannabis during adolescence. Strengthening evidence on causality and teasing out long-term effects of pre-illness cannabis use from continued post-illness has clinical implications for improving schizophrenia outcomes.