Six studies were included in the review (97 participants). One longitudinal study used ethological observations and semi-structured interviews with parents, two studies used pre- versus post-test designs, two studies used cross-over designs and one was a single case study. One cross-over study included two control arms (stuffed dog, ball) in comparison with a therapy dog, the second used standard occupational therapy as the control. Where cross-over designs were used it was not clear if participants were randomised for order of treatment.
Assistance dogs (two studies, 52 participants): Both studies reported positive outcomes including improved safety perceptions, increased social acknowledgments and decreased problematic behaviours. One study that reported cortisol levels found cortisol awakening response decreased when the assistance dog was present in the family, and increased when the dog was removed.
Therapy dogs (four studies, 45 participants): All interventions involved the presence of a therapist and in all four studies interaction with the dogs was observed to dampen social isolation and withdrawal. Three studies reported that therapy dogs promoted verbal and non-verbal behaviours directed towards both dog and therapist.