Amphetamines have shown some promising results in actually curing depression. There is a vicious cycle of depression where the anhedonia and lack of motivation cause the sufferer to allow the underlying causes to get even worse leading to deeper depression. Amphetamines can help break that cycle and ideally even start a virtuous cycle where their use can be tapered and eventually discontinued. It's vitally important though that the drug treatment is combined with behavioral modification so that the artificial stimulation of reward circuits can be operant conditioned on behavior patterns that mitigate the underlying cause of depression. Anyhow I might be off on the jargon since college psychology was a long time ago, but the basic concept strikes me as highly plausible and consistent with what we know about the human mind. And anecdotally I have friends who benefited from amphetamines for depression.

However used improperly it can end in amphetamine addiction or even psychosis. It's not surprising most mainstream psychiatrists don't like to use them for depression, but it is a powerful tool in the box.