I don't think he's depressed, I think he is an immature entitled elitist. Jezebel concocts a scheme to steal Naboth's vineyard. She hires two scoundrels who will bear false witness against Naboth, sends a invitation with the king's seal for a dinner party, arranges for Naboth to sit in a seat of honor with the two hirelings across from him, and crafts an accusation that will give them the legal authority to execute him and take possession of the land. Ahab is just as responsible for it, he is complicit, he allows her to use his seal, he doesn't say no. The elders did a poor job of investigating the accusation. A good interrogator can poke a hole in lies when the evidence is shoddy.