Likely nothing. It depends on the person. Some people with depression do much better on a mood stabilizer than say an SSRI. If the mood stabilizer is Depakote, they may get extremely sleepy on it. Lamictal might have no effect whatsoever. It is just hard to tell and I am broadly generalizing.
Bipolar is extremely hard to diagnose. The DSM-IV cautions practitioners about using only one of the many criteria for diagnosis. When my dx was made, I was on Strattera for adult ADD. It made me manic for the simple reason that I could not sleep when I took it, for the most part. I'd also have days on it where I could not stay awake and had what looked like narcolepsy. I am only manic or hypomanic on Strattera or Ritalin. Take me off, give my body a good six months to wash it out (I am a hypoexcretor) and I am not the least bit manic or hypomanic, but I am still depressed. I can't take SSRIs, or MAOIs or tricyclics, I am allergic to them all. So, the DSM-VI says I might have bipolar because of the problem with SSRIs, etc. Since I am not manic without help, it is PROBABLY a misdiagnosis because it comes down to a single criterium for diagnosis. Do you see what I mean?
For the record, I took Lamictal, which I am allergic to, tried Depakote and could not function due to fatigue and then was on Trileptal for about 8 or 9 months. I don't think any of them did anything other than numb my responses to emotional issues. I didn't give sh__ about anything! I stopped caring if bills were paid or the dishes were done and I didn't care if I had showered in the last week. That actually looks like major depression to me.
What it came down to FOR ME is that I don't believe I have bipolar at all. I am seeing quite clearly that my depressive episodes are related to the onset of my lupus flares. If I don't have a flare for a month, I have no depression symptoms at all. If I become suicidally depressed, I have the presence of mind to understand that I am physically ill and to work on that aspect instead. I find these major depressive episodes to be transcient and lasting as long as it takes me to understand what is going on and make a game plan for coping with the sudden flare of lupus.
This is why I wish that all types of doctors had more time to communicate with one another. My psychiatrist dxd my lupus, my PCP thought I might have bipolar, but kept pumping me full of SSRIs and Strattera. They spoke for all of 5 minutes when the pdoc told my PCP he has diagnosed me with bipolar and was putting me on whatever, then asked what all SSRIs I had been on. He didn't share the lupus diagnosis or anything else pertinent. It was less than helpful with me caught suffering in the middle! The medical situation in the US is a killer.
The Lady Dragonfly
Yes, it was me...I know because I was there when I did it. Lupus sufferer, bipolar II sufferer. Currently on Indocin for chronic pericarditis related to lupus, and cherishing every deep breath without pain. Currently in graduate school for mental health counseling, class of Fall 2007. Vegan and loving it!