“Universal Childcare, Maternal Labor Supply and Family Well-Being” by Michael Baker (University of Toronto), Jonathan Gruber (MIT) and Kevin Milligan (University of British Columbia).
From the study:
“We uncover striking evidence that children are worse off in a variety of behavioural and health dimensions, ranging from aggression to motor-social skills to illness. Our analysis also suggests that the new childcare program led to more hostile, less consistent parenting, worse parental health, and lower-quality parental relationships.”
Note that child:staff ratios have been raised since the data used was collected and are now 8 children age 1 per staff. This would worsen outcomes.