Dogs are unconditional lovers and are well known for being therapeutic animals. Obviously a poorly trained dog is going to be stressful, but well behaved dogs are often used in pediatric hospitals, nursing homes, and Hospice centers as therapy dogs.
Dogs are often used in a variety of therapeutic situations. Studies have shown that people with pets, esp dogs and cats, tend to live longer and suffer fewer heart attacks, strokes and have lower blood pressure.
i believe not only kids but they help people of all ages. i'm not sure how they help but here's an idea dogs are living creatures and they are capable of learning some simple things. so you could play with them and enjoy spending time, looking at them and teaching them some new things. if you are interested in plants i think they also help with depression. i hope this helped :)