Previous research has shown that children who have spent at least some part of their life in an institution tend to have problems with executive function - which is defined as a combination of working memory, the ability to inhibit one's behaviour, forward planning and the ability to move from one task to another - and attention. Past research has concentrated on children aged between six and 11 so researchers at the University of Pittsburgh studied 418 children who had been adopted from institutions in Russia where they had been psychologically, but not physically, deprived. 130 of the children were pre-school age while the rest were older. The study found that the older the age the children had been adopted at the worse their executive function was and that those who were adopted after they were 18 months old had worse executive function than those who had been adopted when they were younger. The onset of adolescence was associated with a greater increase in executive function deficits for children adopted after 18 months than for those adopted when they were younger.
Merz, E. C. and McCall, R. B. Parent ratings of executive functioning in children adopted from psychosocially depriving institutions Journal of Child Psychology and Psychiatry doi: 10.1111/j.1469-7610.2010.02335.x