A comprehensive Swedish twin study involving 921 infants reveals that both genetic and shared environmental factors significantly influence sleep and crying behaviors in early development. Conducted by researchers from Uppsala University, this study tracked the twins at 2 and 5 months, finding a shift from environmental to genetic influences as infants matured. Notably, shared environmental factors accounted for up to 90% of sleep variations at 2 months, while by 5 months, genetics rose to dominate settling behaviors. The study also explored polygenic scores linked to autism, uncovering significant associations with crying duration, highlighting both genetic and environmental contributions to infant behavior.
Source: JCPP Advances