Overview

• Genetics explain about 50% of crying duration at two months and increase to around 70% by five months.
• Unique environmental factors account for the remaining crying variation and significantly influence how rapidly infants settle at two months.
• Sleep routines and nursery conditions emerge as the primary drivers of nighttime awakenings in early infancy.
• Researchers analyzed questionnaire responses from approximately 1,000 Swedish twin pairs at two and five months, comparing identical and fraternal twins.
• Study authors note that the observational design precludes pinpointing specific interventions, highlighting the need for targeted research on effective sleep routines.