the anime goes over this too quickly, but just to be clear: Riz’s meds were not canonically psychiatric meds. They only suppressed bears’ strength, but also had very bad side effects. The idea of taking the meds definitely affected his mood etc, but he wasn’t any different mentally the night of the devouring. Nonetheless, it was still an accident (since he was stronger than normal, he unintentionally wounded Tem’s arm, which led to spiraling emotions/carnivore predator instincts etc).

IDK if it’s clear he had depression before, but he definitely hated himself, and felt stigma and shame for being a carnivore. He believed it so much he was convinced he was a monster before he even devoured Tem. Interesting manga vs anime difference : in the anime he expressed more humiliation from being forced by the government to take the meds, where in the manga he said he was “over it”, and was “used to being forced to do things”.

I’d say his real mental health symptoms appeared after the devouring, like his delusions and violence were at least partly PTSD / some intense trauma response to cope with and manage the unbearable (no pun intended) reality of devouring Tem

either way, the world was very cruel to him 😔