Toxoplasma gondii affects trait anxiety in adult ADHD

TL;DR

This study finds that Toxoplasma gondii infection is linked to lower trait anxiety in adults with ADHD, but not to state anxiety or comorbid anxiety disorders.

Contribution

The first study to show a serointensity-dependent association between T. gondii and trait anxiety in ADHD patients.

Findings

Seropositivity for T. gondii was significantly associated with lower trait anxiety in ADHD patients.

Trait anxiety scores decreased in an IgG-dependent manner in both ADHD patients and all participants.

Comorbid anxiety disorders in ADHD were not linked to latent T. gondii infection.

Abstract

Growing evidence emerges that Toxoplasma gondii (T. gondii) is associated with mental disorders like anxiety disorders or attention-deficit/hyperactivity disorder (ADHD). In ADHD patients around 25% suffer from comorbid anxiety disorders. As the impact of a latent T. gondii infection on anxiety in adult ADHD remains unknown, this study aims to investigate this relationship.

In a case-control study, including 140 participants, venous blood samples were taken of 70 adult ADHD patients and 70 controls for serological analysis of markers of infection and inflammation (leukocytes, C-reactive protein, anti-T. gondii immunoglobulin M (IgM) and anti-T. gondii immunoglobulin G (IgG) (seropositivity), IgG titers (serointensity) as well as anti-T. gondii IgG avidity. The influences on state and trait anxiety were explored using the State-Trait-Anxiety Inventory (STAI).

Seropositivity was significantly associated with the leukocyte count in all participants (n = 140, p = 0.004). Moreover, regression analysis revealed a significant association of seropositivity and serointensity with trait anxiety but not with state anxiety: trait anxiety was significantly lower in seropositive ADHD patients compared to seronegative subjects with ADHD (n = 70, p=0.029). In addition, trait anxiety scores decreased in an IgG-dependent manner in all participants (n = 140, p = 0.028) as well as in the ADHD group (n = 70, p = 0.015). Comorbid anxiety disorders in ADHD were not associated with latent T. gondii infection.

Our data is the first revealing an association between T. gondii and trait anxiety in a serointensity-dependent manner in individuals with ADHD. Further research is needed to clarify the clinical impact of the observed lower trait anxiety in individuals with ADHD and latent T. gondii infection.

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