In general and if used judiciously, yes.
If including something like emotion gives your screenplay flavor and helps paint a better picture of your character or scene, include it. But keep in mind that while it may help the reader, the viewer can’t see “happy;” you have to express that through the actions and dialogue as well.
Accordingly, places like character or setting introductions, the purposes of which are to establish tone or underlying description, are prime for such detail.
ARTHUR GETMAN, 14, sits 15-inches from a 60-inch plasma TV, weeks worth of meals stuck in his braces. His glasses are five years out of style and very bent out of shape, most likely because he doesn’t take them off when he watches TV in bed at night. The two years he’s spent at the bottom of the middle school social hierarchy have weighed heavy on his soul, but you wouldn’t know it by looking at him now; when he’s playing PS3, he may as well be a God.
