Yes, people with a mild degree or level of bipolar can still be bipolar with no obvious manic like behaviours, and it can even be misdiagnosed as just depression sometimes. Bipolar is not a black and white thing, you'd be surprised of all the variations and intensities.
Meds affect is the attempt for stabilization of moods, preventing mood swings, in cases where there are often pretty dramatic swings that can interfer with daily functioning, relationships, etc. There is so much more I can share with you but wouldn't want to bore you or anything like that.
I do not get "manic highs", I am bipolar-II(mild) and mainly suffer the longest with deep dangerous depression, so being the AD's no longer work I have been on a stabilizer (anti-convulsant) called Lamictal (Lamotrogine) which is used for bipolars who have depressions more than mania and only for mild mania is what it is most effective for, this is what I read in several books, journals by the Psychiatry Assoc., and internet so do not quoate me on it, ha!ha!
Take care,
"darkeyes"

In giving advice seek to help, not please your friend
SOLON