Diphenhydramine as a first generation antihistamine acts on a large number of receptors and can even be used as a mild anxiolytic, so I'd guess it could very well have antidepressant effect.
No idea about deliriants like atropine/scopolamine, but in low doses, they were traditionally used to spice up beer (hence Pilsen named for Bilsenkraut, black henbane), so I could imagine short antidepressant effect there too.