Risk factor
Systematic assessment of environmental risk factors for bipolar disorder: an umbrella review of systematic reviews and meta-analyses
Bortolato, B., Kohler, C.A., Evangelou, E., Leon-Caballero, J., Solmi, M., Stubbs, B., Belbasis, L., Pacchiarotti, I., Kessing, L.V., Berk, M., Vieta, E., Carvalho, A.F.
Bipolar Disorder 2017; 19: 84-96
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ObjectivesThe pathophysiology of bipolar disorder is likely to involve both genetic and environmental risk factors. In our study, we aimed to perform a systematic search of environmental risk factors for BD. In addition, we assessed possible hints of bias in this literature, and identified risk factors supported by high epidemiological credibility.
MethodsWe searched the Pubmed/MEDLINE, EMBASE and PsycInfo databases up to 7 October 2016 to identify systematic reviews and meta-analyses of observational studies that assessed associations between putative environmental risk factors and BD. For each meta-analysis, we estimated its summary effect size by means of both random- and fixed-effects models, 95% confidence intervals (CIs), the 95% prediction interval, and heterogeneity. Evidence of small-study effects and excess of significance bias was also assessed.
ResultsSixteen publications met the inclusion criteria (seven meta-analyses and nine qualitative systematic reviews). Fifty-one unique environmental risk factors for BD were evaluated. Six meta-analyses investigated associations with a risk factor for BD. Only irritable bowel syndrome (IBS) emerged as a risk factor for BD supported by convincing evidence (k=6; odds ratio [OR]=2.48; 95% CI=2.35-2.61; P<.001), and childhood adversity was supported by highly suggestive evidence. Asthma and obesity were risk factors for BD supported by suggestive evidence, and seropositivity to Toxoplasma gondii and a history of head injury were supported by weak evidence.
ConclusionsNotwithstanding that several environmental risk factors for BD were identified, few meta-analyses of observational studies were available. Therefore, further well-designed and adequately powered studies are necessary to map the environmental risk factors for BD.
Toxoplasmosis and neuropsychiatric diseases: can serological studies establish a clear relationship?
Fabiani, S., Pinto, B., Bruschi, F.
Neurological Sciences 2013; 34: 417-425
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Toxoplasmosis is a widespread infection, with clinical spectrum ranging from a completely asymptomatic infection to multi-organ involvement. After entering the body, the parasite forms tissue cysts and establishes a chronic infection, involving also the central nervous system (CNS). During the last years, a lot of research has focused on the possible link between exposure to T. gondii and development of neuropsychiatric disorders such as schizophrenia and Parkinson's disease (PD). If a firm association between Toxoplasma infection and neuropsychiatric disorders will be established, this would lead to novel strategies for their prevention and treatment. We will review data from serological and neurodevelopment studies relating infection with T. gondii to such neuropsychiatric diseases.
Association between seropositivity for Toxoplasma gondii, scholastic development of children and risk factors for T-gondii infection.
Ferreira, E. C., Marchioro, A. A., Guedes, T. A., Mota, D. C. G. A., Guilherme, A. L. F., de Araujo, S. M.
Transactions of the Royal Society of Tropical Medicine and Hygiene 2013; 107: 390-396.
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We evaluated the possible association of seropositivity for Toxoplasma gondii and certain risk factors for T. gondii infection with the scholastic development of children.
One hundred children aged 613 years attending the Hospital Municipal de Maring Parana, Brazil, participated in the study. Serologic tests for IgG and IgM anti-T. gondii (indirect immunofluorescence (capture ELISA) were performed. The Scholastic Performance Test (SPT) for writing, mathematics and reading was applied to each child, and the result was classified as high, average or poor. The guardian of each child responded to a questionnaire about certain aspects of the childs living situation and diet.
The prevalence of seropositivity for T. gondii was 8. An association between seropositivity for T. gondii and scholastic development in the mathematics subtest and also consumption of fresh cheese were observed. Children with exposed soil, sand or grass lawn in their peridomicile were 9.116 times more likely to be infected by T. gondii.
The findings showed the need to test school-age children for this parasite, educate families with T. gondii-positive children, provide training to educators, monitor recreation areas, and raise awareness of the need for care in handling food.
Relation of Schizophrenia Prevalence to Latitude, Climate, Fish Consumption, Infant Mortality, and Skin Color: A Role for Prenatal Vitamin D Deficiency and Infections?
Kinney, D. K., Teixeira, P., Hsu, D., Napoleon, S. C., Crowley, D. J., Miller, A., Hyman, W., Huang, E.
Schizophrenia Bulletin 2009; 35: 582-595
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Previous surveys found a large (> 10-fold) variation in schizophrenia prevalence at different geographic sites and a tendency for prevalence to increase with latitude. We conducted meta-analyses of prevalence studies to investigate whether these findings pointed to underlying etiologic factors in schizophrenia or were the result of methodological artifacts or the confounding of sites' latitude with level of healthcare at those sites. We found that these patterns were still present after controlling for an index of healthcare-025EFinfant mortality-025EFand focusing on 49 studies that used similar diagnostic and ascertainment methods. The tendencies for schizophrenia prevalence to increase with both latitude and colder climate were still large and significant and present on several continents. The increase in prevalence with latitude was greater for groups with low fish consumption, darker skin, and higher infant mortality-025EFconsistent with a role of prenatal vitamin D deficiency in schizophrenia. Previous research indicates that poor prenatal healthcare and nutrition increase risk for schizophrenia within the same region. These adverse conditions are more prevalent in developing countries concentrated near the equator, but schizophrenia prevalence is lowest at sites near the equator. This suggests that schizophrenia-producing environmental factors associated with higher latitude may be so powerful they overwhelm protective effects of better healthcare in industrialized countries. The observed patterns of correlations of risk factors with prevalence are consistent with an etiologic role for prenatal vitamin D deficiency and exposure to certain infectious diseases. Research to elucidate environmental factors that underlie variations in schizophrenia prevalence deserves high priority.
Toxoplasma gondii in outpatients with bipolar disorder
Sullens, A., Dickerson, F., Stallings, C., Origoni, A., Moon, J., Yolken, R.
Bipolar Disorders 2007; 9: 101-101