A Common Parasitic Infection May Affect A Person's Mental Health

In yet another reminder that mental health issues can result from physical ailments, a new study published in the Journal of Clinical Psychiatry found that people with rage disorder are twice as likely to have a parasitic infection typically found in undercooked meat, contaminated water and cat feces.

Researchers from the University of Chicago found that the relatively harmless infection, called toxoplasmosis, may be associated with Intermittent Explosive Disorder, a mental health condition that triggers recurrent outbursts of aggression in situations that don't necessarily call for it. 

The study examined 358 adult subjects who were evaluated for IED, among other psychiatric disorders like depression. Volunteers were also scored for signs of impulsivity and aggression, two symptoms of IED, through a psychiatric test. The subjects were then sorted into three groups based on the results: One group had IED, another had other psychiatric conditions and the last group was a control group with no mental illness.

The authors found that the group with IED were twice as likely to test positive for toxoplasmosis than the control group. Nearly 22 percent of the IED group had the infection, compared to just 9 percent of the individuals without mental illness. Approximately 16 percent of those in the "other psychiatric conditions" group had the infection, but reported similar test scores in aggression to the healthy group. Toxoplasmosis-positive individuals scored higher in aggression across all groups. 

It's important to note there are also several caveats with this research. The study used a small sample, for starters. Toxoplasmosis is also relatively common -- an estimated 30 percent of all humans have it -- and most healthy people likely won't show any symptoms, according to the authors.

Plus, the results found that there was a correlation between the mental health disorder and toxoplasmosis, but that doesn't necessarily suggest that the infection causes increased anger issues. 

"We don't yet understand the mechanisms involved -- it could be an increased inflammatory response, direct brain modulation by the parasite, or even reverse causation where aggressive individuals tend to have more cats or eat more undercooked meat," said study co-author Royce Lee, an associate professor of psychiatry and behavioral neuroscience at the University of Chicago, in a statement. "Our study signals the need for more research and more evidence in humans."

In other words, there's no need to worry about your furry friend potentially causing an infection that could lead to increased rage issues (but let's be real, you should probably pass on raw meat, regardless).

However, the results do reiterate that there can be biological factors at play when it comes to mental illness. Another recent study found that depression may be a systemic illness that occurs at a molecular level, and another suggests that people with anxiety fundamentally perceive the world differently . Other research indicates that mental health disorders may be hereditary or stem from changes in the brain .

The main takeaway here is that mental illness is complex, and a person is hardly responsible for having one -- the same way they can't help having an infection like toxoplasmosis. The negative misconception that these conditions are something people "bring on themselves" is increasingly being debunked through research, and that couldn't be more necessary when it comes to a more positive mental health culture.