The Bulbapedia article says nothing about not working with self induced stat drops, just this:
Lash Out deals damage. If any of the user's stats was lowered during the turn this move is used, its base power is doubled to 150.
I think it’s just stat drops in general, after looking at both Serebii and this site also, I haven’t found any evidence that things like Weak Armor wouldn’t work with Lash Out.
Hope this helps! :)