Here's a site that may help.
Bipolar II, Mood Swings without Mania; Brain Tours; Stress and Depression; Hormones and Mood; and more...
Each individual is different. If his symptoms are well controlled with meds, then you may be seeing all there is to see. Sometimes, there needs to be an adjustment in the meds though. Depending upon where he falls in the spectrum of the disorder, the symptomology will be different. Open communication is the best thing there is between the two of you.
Shalom!