How do you tell the difference between mental health issues or medication causing a parent's mood swings?

When I took diet pills some 50 yrs ago, the were uppers. No one realized then there were side effects. I only had to lose 20 lbs and did it in two months so never got addicted.

What you discribe sounds like BiPolar. My cousin wasn't diagnoised till her 40s. Mom needs to get to a doctor for tests.

You say she has been on a diet for 10 years. Do you mean diet pills? Because after a certain amount of time it is a lifestyle and those pills are dangerous long term. Actually there just dangerous, period.

Has she stopped taking them? Could be withdrawal.

She should see a doctor that is aware of the problems she is having. Write a letter and go with her to see the doctor, give it to the nurse for doctor to read before he sees her. If she has been taking over the counter diet pills for 10 years make sure and include that info as well.

This may be way out of line, but is there any chance she is doing drugs? Changes this fast are odd, and sometimes the reason may be bizarre. In my twenties, I worked with a girl who drank perfume for its alcohol content. She didn't smell of alcohol, she didn't get paralytic, and it took months before the boss worked it out. We were all staggered!

Is she under a significant amount of stress? Maybe just too much on her mind. Or could be that she has an infection of some sort. A trip to the doc may be worthwhile.