https://en.wikipedia.org/wiki/René_Spitz
In 1935, Spitz began research in the area of child development.
He was one of the first researchers who used direct child observation
as an experimental method—studying both healthy and unhealthy subjects.
His greatest scientific contributions came from his studies of the
effects of maternal and emotional deprivation on infants.
In 1945, Spitz investigated hospitalism in children in a foundling home.
He found that the developmental imbalance caused by the unfavorable
environmental conditions during the children's first year produces
irreparable psychosomatic damage to normal infants.
Edit: https://en.wikipedia.org/wiki/Maternal_deprivation