SOURCE: Coccaro EF, Lee R, Groer MW, et al. Toxoplasma gondii infection: Relationship with aggression in psychiatric subjects. J Clin Psychiatry 2016;77:334-341.

Many have followed an evolution of medical disorders surprisingly linked to infectious diseases: cervical cancer (human papillomavirus infection), gastric and peptic ulcer disease (Helicobacter pylori), and even obesity (adenovirus 36). Toxoplasma gondii (TXG) is a highly prevalent protozoan reportedly infecting, albeit usually asymptomatically, as many as one-third of U.S. adults. Humans can acquire TXG from household cat feces and less commonly from undercooked meat infected with TXG. In immunocompetent humans, TXG lives in the central nervous system within neurons and glial cells and is generally asymptomatic, although associations between latent TXG and schizophrenia, bipolar disease, and personality disorders have been demonstrated.

Coccaro et al performed sero-analyses on 358 adults comprised of approximately three equally sized groups: healthy controls, psychiatric controls without noteworthy aggression issues, and psychiatric patients with intermittent explosive disorder. A TXG IgG antibody titer > 12 IU was regarded as seropositive.

Positive TXG sero-status was statistically significantly associated with aggression. Prevalence of TXG seropositivity ranged from 9.1% in healthy controls to 16.7% in psychiatric controls (without aggression issues) to 21.8% in subjects with intermittent explosive disorder. These preliminary results do not include any advice about if, how, or when TXG treatment should be considered.