- Study involves 921 twins to assess sleep and crying.
- Data collected at 2 and 5 months of age.
- Shift from environmental to genetic influences noted between ages.
- 61%-90% of nighttime variations attributed to shared environment at 2 months.
- Heritability of settling behavior increased to 51 percent to 67 percent by 5 months.
- Polygenic scores linked to autism associated with crying duration.
- Sibling interaction effects observed in infant behaviors.
- Study limitations include reliance on parent-reported data.
Source: JCPP Advances
