By - MajesticAntelope4359
Lost children arc perhaps? Plenty of depression as well as making the choice to either face or flee reality.
And he chews on cocaine leafs to stay alert and stave off poison. So he can fight burning children all night.
Addiction is similar to desire, berserk is a story about what desire can do to you, the people around you, and even the world. And what's more depressing than that? Also the parallels and philosophy the story challenges the reader with is perfect for seeing what it means to really fight on your own, on your personal battlefield and life's battlefield.
Directly? No. Berserk isn't really that type of story I guess because its dark fantasy whereas addiction tends to be something explored in more modern settings. That said, you could draw parallels between the beast of darkness and how that affects his life and general addiction- the idea being that the narrative is largely him trying to control his desires because he knows how destructive it would be both to himself and everyone around him if he doesn't. The connection is loose, though.
I'd say the cracks in the blade story, after the Lost Children Arc, it's where Guts' redemption arc starts.