You answer:

Not only is it known, but I also know that it is actively used. After all, dogs are very responsive and loving animals. However, not every dog ​​is suitable for such treatment. As far as I know, such dogs undergo special training and then they are registered in the official database. As an example. here is the organization https://myserviceanimal.org/ which provides services in this direction. As far as I know, you can both get such a dog for therapy and register it.