When, thank heavens, you return to feeling normal again after being depressed, everything around you will seem to have greater clarity. Colours will be more vivid. Music will be more melodic. And according to a report in New Scientist, smells will be stronger. (This could be good or bad depending on whether we're talking about the perfume of a rose or the pong of someone's whiffy old trainers, of course.)
More specifically the article details research undertaken at the University of Dresden, showing that people's sense of smell diminished when they were depressed. Amazingly this seems to happen because the part of the brain responsible for registering smells - the olfactory bulb - actually gets smaller, which was observed using magnetic resonance imaging (MRI). It's fascinating to see the evidence building up which supports what I think we instinctively know. When you're depressed, you feel cut off from everything.