Unclear. But maybe. Especially in the womb.

Unlike Canli, McIntyre implicates inflammation in general, not exclusively inflammation caused by infection or direct effects of infection itself, as a major contributor to mental maladies. "It's unlikely that most people with a mental illness have it as a result of infection," he says, "But it would be reasonable to hypothesize that a subpopulation of people with depression or bipolar disorder or schizophrenia ended up that way because an infection activated their immune-inflammatory system." McIntyre says that infection, particularly in the womb, could work in concert with genetics, psychosocial factors and our diet and microbiome to influence immune and inflammatory activity and, in turn, our risk of psychiatric disease.

The idea that inflammation – whether stirred up by infection or other factors — contributes to or causes mental illness comes with caveats, at least in terms of potential treatments. Trials testing anti-inflammatory drugs have been overall mixed or underwhelming.

Could it be... toxoplasmosis!?!?!

I woke up feeling fine and then I read THIS:

Up to half of the world's population is infected with toxoplasmosis.[8] In the United States about 23% are affected[9] and in some areas of the world this is up to 95%.[1]

Halibutboy says it's caused by cat litter boxes. 

http://pandawhale.com/post/68211/does-fungus-cause-alzheimers

The NPR article says:

Harkening back to Adolph Meyer's early 20th century theory, Canli notes how certain infections of the brain – perhaps most notably Toxoplasma gondii — can result in emotional disturbances that mimic psychiatric conditions. He also notes that numerous pathogens have been associated with mental illnesses, including Borna disease virus, Epstein-Barr and certain strains of herpes, including varicella zoster, the virus that causes chickenpox and shingles.