
Whilst acknowledging that the social dog can be very upset if forced to live a solitary life for many hours of the waking day, I also believe that 'separation anxiety' is an over-worked term for what is bad behaviour, or simply a dog who is a round peg in a square hole.
However, there's no dubt that we are into an age where all too often, all the members of a household are out during the day, either at work or at school, leaving the dog, often a 'I want' dog of completely the wrong breed for the circumstances. So what's going on is labelled 'separation anxiety'. My main breed(s) - hounds - do NOT do well living a solitary life. They are pack animals and are way happier living within a busy family situation.
We didn't have a dog (hound) until we were financially able for me to stop working full time. Which I did for 6 months before going back for 3 hours in the middle of the day. He wasn't impressed and went back to peeing around the house. I took him with me and he stayed in the car, with staff visiting him, walking him. The carpark was close by and tree covered (shade) and that summer wasn't a hot one. Once I could stop working at all, I did. Had it been otherwise, there'd have been NO DOG. Quite literally. Sadly people want it ALL these days and I wish they'd get a cat rather than a dog, so far fewer dogs would be in an unsuitable home, and unhappy.
Research? It's there for all to see without that, I suggest.