I wonder if it's like werewolfism, like if we can find the original depressed person and put a silver bullet in their head, will it cure everyone else's depression that they have infected?

It's worth a shot, right?

They identified managers who either had mental health issues themselves or came from struggling companies as the main “carriers” of mental disorders within a workplace.

You mean if your boss is miserable, you are going to be also? I guess you need to have numbers to technically prove something, but let's be honest it is nothing new.
Misery begets misery.