What It Really Means to “Catch” a Mental Illness

sad woman sitting alone

The book Infectious Madness, by award-winning author Harriet Washington, promises to explain to readers “The Surprising Science of How We ‘Catch’ Mental Illness.” On today’s show, we discussed the provocative idea put forth in this title with Ms. Washington and psychiatrist Dr. Gail Saltz.

Here’s a major spoiler—but don’t stop reading because this is important: Mental illness is not contagious, at least not in the traditional sense. You can’t catch things like schizophrenia, OCD, or bipolar disorder from someone who has it the way you can catch the flu or other infectious disease.

So what is Harriet talking about when she says you can catch a mental disease?

While the cause of mental illness is for the most part still a big mystery, we do know it’s the result of a combination of genetic, psychosocial, and environmental factors. On the show we talked about the uncomfortable idea that infectious agents like viruses, bacteria, or parasites may also play a key role.

At first it might seem odd to suggest that infectious organisms might contribute to mental illness, but it’s actually not a new idea. We know that infections like syphilis for example can affect the brain and cause personality changes. Gangster Al Capone suffered from the debilitating effects of syphilis that attacked his brain, and it’s even hypothesized that it could have precipitated some of his infamous behavior. Psychiatrists always test for this and other infections when a new patient presents symptoms, but the idea that an infection early in childhood may lead to mental illness is a paradigm shift for us in medicine.

On the show we learned that as much as 15 to 20 percent of mental illness may be attributed to exposure to harmful microorganisms like the bacteria that cause strep throat or the parasite that causes Toxoplasmosis. This is troubling, but it also could be good news. First piece of good news: not everyone who gets infected with these bugs develops mental illness. These infectious agents are just one of the factors in the development of mental illness, and it’s only in those people who are otherwise predisposed to develop the condition. And for most people these infections probably happen in childhood or even in utero. Second piece of good news: understanding the factors that lead to mental illness could better help us to treat and actually prevent it.

On the show Harriet challenged us to start thinking more about this issue, and the importance of this was demonstrated when we met someone with what appeared at first to be a “traditional” mental illness, but turned out to be a condition that many of us in medicine haven’t yet even heard of. It’s a group of conditions known as PANDAS (Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal Infections), which was championed by Dr. Susan Swedo and is now accepted by most scientists and the NIH.

Kids with PANDAS present with sudden onset of symptoms of obsessive-compulsive disorder and tics. The sudden onset is key here because it suggests that the disease was caused by a specific event. The other part of the diagnosis is that the symptoms occur after a streptococcal infection (like strep throat). There can also be other accompanying changes such as increased emotional reactivity and regression to a previous level of dependency. The condition can be diagnosed through patient history and a blood test for strep antibodies. The good news is that in many cases it can also be successfully treated. The bad news is that our understanding of this condition is relatively new, so your doctor may not even know about it. For more information about PANDAS (or PANS, a broader category of disease characterized by neuropsychiatric syndromes precipitated by a broader range of infectious and environmental factors) check out the NIH website and the PANDAS Network.

While PANDAS/PANS is incredibly interesting and important, unfortunately we haven’t yet found anything else like it, and it’s probably unlikely that this research will lead to new treatments for things like schizophrenia. This research may however help us to develop new methods of prevention. For example researchers from Johns Hopkins and the Stanley Research Institute have implicated both something called an endemic retrovirus (basically a virus that inserted itself into human DNA as long time ago and now is passed from generation to generation) as well as Toxoplasma gondii and the flu virus as possible precipitating factors for some people with schizophrenia. Toxoplasma is the infamous parasite spread by cats. Harriet suggests that open sandboxes are popular amongst cats and a potential reservoir for the parasite. Avoiding public sandboxes and making sure sandboxes at your home are covered when not in use may help prevent their contamination and infection of children. And of course getting annual flu shots can help prevent the spread of flu and maybe in some even help prevent schizophrenia.

If you want to learn more definitely check out the book Infectious Madness.