Increased CO2 exposure is one possibility, both from increased atmospheric levels, and from more thermal insulation of buildings: https://thinkprogress.org/exc

Increased CO2 exposure is one possibility, both from increased atmospheric levels, and from more thermal insulation of buildings: https://thinkprogress.org/exclusive-elevated-co2-levels-directly-affect-human-cognition-new-harvard-study-shows-2748e7378941/ https://thinkprogress.org/exclusive-elevated-co2-levels-dire...