The theory of course is that if you're too intelligent you get sad because you're too intelligent.
So the idea comes to you that you could simply inflict some blunt force trauma to your head regions and thus makes yourself less intelligent until you become happy. However this approach has downsides.
First, what if you're not sad because you're too smart and you are in fact too stupid to know this? Then making yourself stupider will not help you. It might in fact make you even sadder.
Second, what if this actually works but you get hooked on the blunt force trauma? When do you stop? When your head is so caved in your motor functions stop letting you continue?
So, no, sir mister police officer, I will not stop smoking this weed thank you very much.
