Well, the hinges on the right side are both screwed and glued. Each hinge has 4 + 4 screws, good thick screws that reach almost to the other side of the stair. The glue is construction glue.
On the left side, the hinges are on the bottom of the step so it's naturally stronger. If heavy things are going up we can just stay left. The stairs are mostly just used by my daughter who is small, so I think it should be good.