If you eat something that takes away a stat point, say, personality -1, but you did not notice you would suffer the hit before you ate it, how can you find out what it is that is robbing you of points? For example, I went to pick a lock, and it told me I needed a skill of 25 to pick this lock. Well, my lockpick skill was at 30, but was reduced to 23 with a - sign next to it. In Oblivion a damaged stat would indicate what spell, apparel or ingested item was causing the problem. Can you find that out in this game or are you just in the dark?

The EFFects submenu in the Status tab of your Pip-Boy.

Go to the stats screen, it has a page about current char effects.