Associations of mental disorders and neurotropic parasitic diseases: a meta-analysis in developing and emerging countries

Abstract

Background: Although they are declining worldwide, neurotropic parasitic diseases are still common in developing and emerging countries. The aim of this study was to estimate the pooled prevalence and pooled association measures of comorbidities between mental disorders (anxiety, depression, bipolar disorder, and schizophrenia) and neurotropic parasitic diseases (malaria, cysticercosis, toxoplasmosis, human African trypanosomiasis, Chagas disease, and human toxocariasis) in developing and emerging countries.

Methods: As the first meta-analysis on this topic, this study was performed in accordance with PRISMA guidelines. The protocol was registered in PROSPERO (N°CRD42017056521). The Medline, Embase, Lilacs, and Institute of Epidemiology and Tropical Neurology databases were used to search for articles without any restriction in language or date. We evaluated the quality of studies independently by two investigators using the Downs and Black assessment grid and pooled estimates using the random-effects method from CMA (Comprehensive Meta Analysis) Version 3.0.

Results: In total, 18 studies published between 1997 and 2016 met our inclusion criteria. We found that the prevalence of anxiety and depression in people suffering from Chagas disease and/or neurocysticercosis was 44.9% (95% CI, 34.4-55.9). In 16 pooled studies that included 1782 people with mental disorders and 1776 controls, toxoplasmosis and/or toxocariasis were associated with increased risk of schizophrenia and/or bipolar disorders (odds ratio = 2.3; 95% CI, 1.7-3.2). Finally, toxocariasis and/or toxoplasmosis were associated with an increased risk of the onset of schizophrenia (odds ratio = 2.4; 95% CI, 1.7-3.4).

Conclusion: Our pooled estimates show that the associations between diseases studied are relatively high in developing and emerging countries. This meta-analysis supports the hypothesis that toxoplasmosis could be the cause of schizophrenia. These findings could prove useful to researchers who want to further explore and understand the associations studied.

Keywords: Association; Co-morbidities; Mental disorders; Meta-analysis; Neurotropic parasitic diseases.

Fig. 1

Research strategy flow chart for the meta-analysis of associations of mental disorders and neurotropic parasitic diseases in developing and emerging countries

Fig. 2

Forest plot of the pooled prevalence of anxiety and/or depression in people with Chagas disease and/or neurocysticercosis. Heterogeneity: Q = 1.56, df = 1, p = 0.21, I² = 36.03

Fig. 3

Forest plot of the pooled odds ratio of toxoplasmosis and/or toxocariasis in people with schizophrenia and/or bipolar disorders, Heterogeneity: Q = 62.67, df = 16, p < 0.0001, I² = 74.47, Kheirandish et al., 2016*: Schizophrenia, Kheirandish et al., 2016**: Bipolar disorders

Fig. 4

Funnel plot showing found and missing analytical studies of associations of mental disorders and neurotropic parasitic diseases

Fig. 5

Forest plot of the pooled odds ratio of associations of mental disorders and neurotropic parasitic diseases by type of subjects (hospitalised and non-hospitalised). Heterogeneity: Q = 62.67, df = 16, p < 0.0001, I2 = 74.47, Kheirandish et al., 2016*: Schizophrenia, Kheirandish et al., 2016**: Bipolar disorders