All of the above are correct.
What kind of dog are we talking about?
My dog had Separation Anxiety as well. Talk to your vet about it. There are meds avail, yes. But there's also thing you can do to help minimize the anxiety that they feel.
You need to think about what is going on in the house when you are there, such as TV's, Stereos. If they are usually on when you are there, leave them on when you leave.
Don't make a big deal about it when you leave OR come home. Your dog will be excited to see you when you get home. Practice ignoring it for the first few minutes and don't act overly excited to see him. Keep a level range of emotion, coming and going.
Good luck with it.
PT