Earlier quoted context omitted.
Feeling slightly happy is better than being totally depressed.
By depression, I assume you mean sadness? Existential angst? Because if someone found smiling could curtail depression I'm sure they'd win the Nobel prize. I thing it's evident that smiling can make a ratty external situation more humorous, but for internal darkness it's like bottling things up, which I'm surprised psychologists might have thought to be a good idea.
You're reading way too far into that. If something brings you from -100 to -95 it's notable but not world-changing. yamike didn't say anything about actually fixing the depression, just adding a slight bit of happiness.
> I think it's evident
Are you basing that on anything? There's a reason we're actually doing this study and not just reasoning out the answer.