I have heard good things. They say the child could bond with the bog and if they are non verbal they will even start talking to the dog. The best I have heard is a guide dog for autistic children. They are trained to help with tantrums, bolting and a lot more.
We have a english mastiff that so far does really good with her.
We have a golden retriever with our 5-year grandson and she is amazing with him. He was a runner til Daisy Dog stayed with him. Now it is like why bother, I cannot get away from her! LOL