Sentence:  "The risk of psychotic disorder in the population exposed to <WSD>urbanicity</WSD> alone was 1.59% (31/1946), the risk in those exposed to family history, broadly defined, alone was 3.01%" ... / "Thus, between 60% and 70% of the individuals exposed to both <WSD>urbanicity</WSD> and family history had developed psychotic disorder because of the synergistic action of the two proxy causes". 
Meaning of the word marked with <WSD> tags:  The quality or fact of (an area) being urban.