Lynda Sharpe roots it out:
Plunk two little rats together and it’s almost impossible to stop them whooping it up. But thwart a young rat’s zeal for play (by rearing it alone or with drugged companions that won’t play) and you create an adult that loses its cool in social situations. When things start getting edgy, play-deprived rats either succumb to rat-rage or scarper, quaking, to a corner. And the lack of play is responsible, because if you let an isolated rat fool around for just one hour daily, it turns into a normal chilled dude
The Dish 