One of my dogs suffers from terrible panic attacks when there's thunder... panting and shaking like a leaf. For many hours this year because this year's thunderstorms have been biblical in size, lasting 12 hours. I was actually afraid he might have a heart attack, so I got some trazodone for him. Given an hour or so before any noise STARTS, it works pretty well to knock the panic attacks down about 50%, at least to a manageable level. But it's awful watching one of your "kids" suffer.
And now because of weeks of thunderstorms/panic, he seems to be suffering from PTSD... ANY noise he hears that's "boom" like (like even my wife walking hard across the upstairs floor), he gets very alert, as if he's saying "uh-oh... what was that?" He also seems to not want to be outside much anymore, has turned semi-agoraphobic, and seems depressed. As the words come out of my mouth, they seem almost silly, to be talking about a dog, but having now lived it, it's absolutely real.