Why on earth are these studies even necessary? Pressure makes you talk less to people. Just putting two remotely related words together doesn't automatically make it insightful.
Given how important parental interaction is for healthy child development (See: Language deprivation [1]), it is useful to bring up the issue so that more attention is given to this particular set of long-term effects. More attention will help social work trying to create a counterbalance.
[1] https://en.wikipedia.org/wiki/Language_deprivation