The effect that staying up late has on a person, similar to the effects of drunkenness. Victims often say and do silly, inappropriate, or personal things that they would not if it were not so late.
The effects may set in at different times of night for different people, depending on when they consider being "up late" to occur.
Someone may share embarrassing stories, secrets about friends, or personal relationship drama when they are suffering from LND.
People often follow these stories with comments like: "Wow, I wouldn't have told you that if it wasn't so late! I must be suffering from Late Night Drunkenness (LND)!"