Dopamine and Polio
Question: I found the brain stem and hippocampus could have been affected by polio. This is where dopamine is produced. Research shows people with polio are 40% more likely to be schizophrenic because of lower levels of dopamine. Lack of dopamine is probably what causes schizophrenia.
Dr. Bruno’s Response: The question misquotes Nielsen’s 2007 Danish database study of polio survivors. The study does not say that, “Research shows people with polio are 40% more likely to be schizophrenic because of lower levels of dopamine.” Nielsen didn't mention schizophrenia or dopamine, but stated, “Overall, history of poliomyelitis was associated with a 40% increased risk of being hospitalized for a psychiatric disorder. The overall increased risk of psychiatric hospitalizations could not be confined to specific groups of psychiatric disorders. Rather, there seemed to be slightly increased risks of several different disorders, especially milder psychiatric disorders. These included personality disorders, substance/alcohol abuse, and other non-psychotic mental disorders," not schizophrenia. (Note: the Italics are mine.)
Nielsen continued: “The reason for the higher odds of having mental problems isn’t really known, but it might related to the very painful and fearful experience of contracting polio, the stringent isolation from family for several weeks, and the difficulties of then overcoming physical handicaps and social prejudice,” not low levels of dopamine. (reuters.com/article/us-polio-psychiatric-ills/poliovictims-may-suffer-psychiatric-ills-later-idUSKIM67022820070206)
There is a 1997 paper by Eagles suggesting a potential relationship between polio and schizophrenia, which is a hypothesis based on coincidences, not research. Squires addresses the failings of Eagles' hypothesis. (link.springer.com/article/10.1023/A:1022486423238)
Actually, a decrease in dopamine should REDUCE, not increase, the incidence of schizophrenia. In fact, schizophrenia is treated with antipsychotic medications that block the action of dopamine in the brain. (www.netdoctor.co.uk/medicines/brain-nervous-system/a7483/risperdal-risperidone/)
Both David Bodian's research from the 1940’s and our studies found polio survivors showing evidence of a decrease in brain dopamine due to poliovirus damage to the basal ganglia that produce dopamine, not the brainstem and hippocampus, which do not.