Uppity your second link was a brief reference to the results of your third link which has been analysed more carefully by psychology today, and i quote:
"One difficulty with disseminating this conclusion is that the study is not yet published, meaning that it has not yet passed the rigorous peer-review that is required for publication in a scientific journal. Instead, the results were simply reported in a Harvard news release.
....
the results of [this] meta-analysis are actually more nuanced than that:
The results actually show that early daycare is associated with better outcomes only for kids growing up in single parent, low-income families.
In the researchers' own words,
"...moderator analyses indicated that early maternal employment was associated with beneficial child outcomes when families were at risk socioeconomically, particularly in the context of families with single parents and on welfare; these findings support the compensatory hypothesis of employment for these families (e.g., NICHD Early Child Care Research Network, 2003)." ...
"In contrast, other analyses indicated that employment was associated with negative child outcomes when families were not at risk financially (i.e., when families were middle or upper-middle class); these findings support the lost-resources hypothesis for these types of families (e.g., NICHD Early Child Care Research Network, 2003)."
The timing of maternal employment also mattered. Infant daycare during the first year of life proved to be detrimental: "Timing of employment was also an important moderator, such that Year 1 employment was negatively associated with children’s achievement, whereas later employment (Years 2 and 3) was positively associated with achievement." The results highlighted in the Times article would seem to suggest that there is no need for parental leave programs because children are actually helped rather than harmed by early introduction to daycare. Yet a more careful reading of the results suggests a very different conclusion, namely, that daycare is beneficial during the first year of life only for low-income single mothers who are overwhelmed from trying to do it all themselves.
.... Another factor that looms large in research on childcare is the wide variability in outcome based on the type of care and instruction provided by the daycare center.... "