An Update on the Epidemiology of Schizophrenia with a Special Reference to Clinically Important Risk Factors

Does college education reduce the risk of schizophrenia? Evidence from a college enrollment expansion policy in China

BACKGROUND

Schizophrenia occurs worldwide, and the health, and economic burden is substantial. As one of the common proxies of socioeconomic status (SES), education was reported to be associated with the risk of developing schizophrenia. However, there is no causal evidence about the relationship. This paper explores the health benefits of college education for schizophrenia.

METHOD

Based on exogenous variation in college enrollment across regions and cohorts induced by college enrollment expansion policy, we use instrument variable (IV) estimate strategy to estimate impacts of college education on the risk of schizophrenia with the data from Second National Sample Survey on Disability.

RESULTS

We find that college education reduces the risk of developing schizophrenia by 4.2 percentage points. Some further analyses suggest the causal protective effect is only found among men, rural, and low-income individuals.

CONCLUSIONS

These findings provide new evidence for the causal relationship between college education and schizophrenia, and add to the literature on the health benefits of education.

A systematic review and meta-analysis of the incidence of psychotic disorders: the distribution of rates and the influence of gender, urbanicity, immigration and socio-economic level

BACKGROUND

Considering existing knowledge on the relationship between certain environmental factors and incidence rates of psychosis, we carried out a systematic review to provide a broad and updated picture of the incidences of different psychotic disorder subgroups worldwide and how some environmental factors influence these rates.

METHODS

Studies with original data related to the incidence of psychosis (published between 2000 and 2015) were identified via searching electronic databases (CINAHL, MEDLINE, PSYCINFO, PUBMED, and SCOPUS). Data on the following risk factors were extracted: gender, urbanicity, immigration and socio-economic level. Descriptive appraisals of variation in incidence rates (IR) and incidence rate ratios (IRR), with a 95% confidence interval were calculated. In addition, a meta-analysis was performed to calculate IR pooled by diagnosis group and IRR pooled by diagnosis and gender, urbanity, immigration and socio-economic level, using a random effects model.

RESULTS

We identified 33 reports to analyse. Overall IR per 100 000 persons for non-affective psychoses (IR pooled = 22.53 (16.51-28.54)) were higher than affective psychoses (IR pooled = 7.12 (5.03-9.22)). There was an increase in rates of psychosis in men v. women (IRR pooled = 1.54 (1.37-1.72)), in urban v. rural areas (IRR pooled = 1.64 (1.38-1.95)), in immigrants v. natives (IRR pooled = 3.09 (2.74-3.49)), and in lower socio-economic level areas (IRR pooled = 1.78 (1.43-2.22)).

CONCLUSIONS

IR among different psychotic disorders was found to vary depending on gender, urbanicity, and immigration (as most of the previous literature focuses on non-affective psychosis or schizophrenia).

Genetic Risk and Outcome of Psychosis (GROUP), a multi-site longitudinal cohort study focused on gene-environment interaction: objectives, sample characteristics, recruitment and assessment methods

OBJECTIVE

A longitudinal focus on gene-environment vulnerability and resilience in both patients, their unaffected family members and non-related controls offers the opportunity to elucidate etiological and pathogenetic factors influencing the onset and course of psychotic disorders. The current paper delineates the objectives, sample characteristics, recruitment and assessment procedures of the Genetic Risk and Outcome of Psychoses (GROUP) study.

METHODS

A naturalistic longitudinal cohort study with assessments at baseline, after three and six years of follow-up. The study is conducted by a consortium of four university psychiatric centres, with their affiliated mental health care institutions in the Netherlands covering more than 7.5 million inhabitants. Extensive assessment of genetic factors, environmental factors, (endo)phenotypes, and outcome.

RESULTS

At baseline, 1120 patients, 1057 siblings, 919 parents and 590 healthy controls were included.

CONCLUSION

The GROUP study will contribute to insight in risk and protective factors in the aetiology of non-affective psychotic disorders, and in the variation in their course and outcome.