Table 4. Studies on the impact of isolation on childhood in the area of cognitive and social development and in the area of the hypothalamic-pituitary-adrenal axis.

Author	Data collection/social isolation criteria	Theme	Results	Limitations
Fox et al. 19	Collection of data on children's birth and previous health. Evaluation of the relationship with the caregiver, language development and IQ at 30, 42, 54 and 96 months of age. Children in foster care institutions were considered to be in social isolation.	Cognitive and social development	Institutionalization during childhood results in the child's social isolation and becomes detrimental to his cognitive and social development.	Many of the children in the intervention and control groups were no longer residing in their original location.
Martin et al. 15	Video recordings of behavior in interactions and play in the school environment. Evaluation of cortisol and sIgA levels in saliva samples. The criterion for isolation was the behavioral patterns presented by each child.	Hypothalamic-pituitary-adrenal axis	Social isolation was the only behavioral pattern that increased cortisol levels.	The samples were collected in only one type of situation experienced by the children (games).
Koss et al. 16	Home collection of salivary cortisol in three samples (morning, noon, bedtime), for three days. In the same period, care in the pre-adoption period, the child's growth and socio-emotional capacity were evaluated. Children in foster care institutions were considered to be in social isolation.	Hypothalamic-pituitary-adrenal axis	Children in isolation exhibited less pronounced daytime cortisol compared to non-isolated peers of the same age; these differences did not diminish over the two-year period. It was found that early social deprivation can contribute to the early programming of the hypothalamic-pituitary axis.	Some families refused to participate in the study. Of those who agreed, not all were able to start shortly after adoption and therefore were not included in this analysis. The collection of all samples was a challenge for some of them and required several weeks, extending the time period for each collection.

IQ: intelligence quotient; sIgA: secreted immunoglobulin A.