Totally Stable

What psychological disorder might my mom have?

My 50 year old mom has always been pretty normal and relatively emotionally stable, but over the past few years she seems to have become a little unhinged.

During the day, she appears to be totally fine and it completely lucid and normal. However, after about 7 or 8 in the evening, she becomes agitated very easily and is very illogical. She becomes completely irrational and does things that she would never normally do (for instance, the other night she yelled and swore at my brothers fiance for no apparent reason, and they are generally on very good terms)

Are there any psychological disorders that would cause this rapid change in personality and mental state as the time of day progresses? And if so, should I try to make her see a shrink?

major depression, because your more depressed at night then you are in the morning

she might also have OCD

but based on you question, i think she most likely has an anxiety disorder, and you should take her to the doctors.