**2. Epidemiologic data on the association between toxoplasmosis and schizophrenia**

One of the first approaches adopted to explore a possible relationship between *T. gondii* infec‐ tion and schizophrenia was to analyze epidemiological data on the two diseases. Initial con‐ clusions were as follows:

• Both have a familial incidence. This is explained in the case of schizophrenia by the pos‐ sible participation of certain genes in its pathogeny [21], and in the case of toxoplasmosis by the possible common exposure of family members to the parasite, although a genetic influence has also been proposed [22].


These and other published findings indicate that the two diseases have some similar features and may even be epidemiologically related. However, they are inadequate to establish etio‐ logical relationships, and a pathophysiological approach is required to explore causality.
