You can't exactly "catch" a mental illness, but some infections like strep throat can affect your brain and behavior, research suggests. A field called immunopsychiatry has emerged, and it studies the possibility that inflammation or an overactive immune system are linked to mental disorders such as depression, schizophrenia, and Alzheimer's disease.
Pediatric autoimmune neuropsychiatric disorders associated with streptococci, or PANDAS, is one such diagnosis that links brain health with body health. When a person has PANDAS, the body's immune system, while attempting to eliminate a strep infection, sometimes attacks parts of the brain that help regulate motion and behavior. This then causes the person to experience symptoms like those of someone with obsessive compulsive disorder, schizophrenia or deep depression. Eliminating the inflammation, some doctors say, restores normal brain function. Syphilis, celiac disease and lupus are among other conditions that have been linked to immunopsychiatry.
The study of immunopsychiatry isn't universally accepted, and diagnosing someone with a condition like PANDAS is still controversial, but knowing that at least some mental disorders can be caused by infection gives doctors more options to explore when looking for diagnoses. Those who support or oppose PANDAS both agree that mental disorders should be looked at as a set of symptoms with a variety of possible causes.