Toxoplasma gondii infection and risk of attention-deficit hyperactivity disorder: a systematic review and meta-analysis

ABSTRACT

Toxoplasma gondii (T. gondii), as an opportunistic neurotropic parasite of the Apicomplexa family, was firstly described in 1908. As attention-deficit hyperactivity disorder (ADHD) is one of the most common neuropsychiatric disorders in children and adolescents and often persists into adulthood, the purpose of this systematic review and meta-analysis was to investigate the relationship between T. gondii infection and ADHD.The data were systematically collected from seven electronic databases up to May 1^st 2019 with no language restriction. This study was registered at the International Prospective Register of Systematic Reviews (PROSPERO; code: CRD42020149353). Odds ratios (ORs) and 95% confidence intervals (CI) were estimated using a random effects model. Seven studies involving five cross-sectional and two case-control studies were included in this meta-analysis.Results indicated that there was a statistically non-significant association between exposure to T. gondii infection and increased risk of ADHD based on the detection of immunoglobulin G (IgG) antibody (2.02 [95% CI: 0.97-4.20]; I²=58.7%). However, obtained results of Egger’s tests for anti-T. gondii IgG antibody showed publication bias (P=0.014).Sensitivity analysis revealed stable results for the association between anti-T. gondii IgG antibody with ADHD.Given the small number of studies in this field and the obtained results, it cannot be conclusively stated that T. gondii is a risk factor for ADHD.It is important to have reliable information about the relationship between T. gondii and ADHD around the world; as it may lead to better insight to elucidate the possible association of toxoplasmosis and the pathogenesis of ADHD.

KEYWORDS:

• Toxoplasma gondii
• toxoplasmosis
• attention-deficit hyperactivity disorder
• ADHD

Acknowledgments

This article is the approved plan (No. 6376) from the Student Research Committee of Mazandaran University of Medical Sciences, Sari, Iran. The code of ethics of this plan is (IR.MAZUMS.REC.1398.5504).

Author Contributions

AD conceived the idea for this meta-analysis. TN and SS searched the databases for potentially eligible articles based on their titles and abstracts. ZH and TN extracted the data. MM analyzed the data. AD and TN participated in the study design and wrote the manuscript. AD and AA critically reviewed the manuscript. All authors read and approved the final manuscript for publication.

Disclosure Statement

No potential conflict of interest was reported by the authors.

Supplementary Materials

Supplemental data for this article can be accessed here.

Additional information

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.