Not exactly. It's a different kind of chemical comedown, similar to what's called "drop" in the bdsm world. People get so excited about finally doing what they love with people who accept them, and then the actual excitement of doing those things spins off lots of natural chemical highs. When they have to leave they're both depressed in general that they have to leave those things/people behind, and then also have a drop off of those natural "high" chemicals. It's common for people who leave non-drug-related conferences or weekend-long parties to be affected by it, for up to a week or more.