Figure 3. Illustration of a putative three-stage progression toward disease for Global IQ impairment.

The first stage would extend from conception/pregnancy until 3 to 6 years old and would be characterized by a phenotypic decline of 5–8 points and/or ontogenetic delay in children at risk. During the second stage, from primary school years until young adulthood, youths at risk would present a stable IQ deficit. The third stage, beginning around the prodromal years, illustrates the drop of 5–8 points of IQ suffered by patients. Dotted lines represent sequences of change or decline periods during the life of an individual, plain lines represent stability period in IQ. This study encompassed only the period of Primary school, adolescence and young adulthood.