Subjects will be recruited from the greater Madison, WI area. Hypersomnolent subject groups (n=30 in each group) may include unipolar MDD with hypersomnolence, primary hypersomnia (idiopathic hypersomnia), bipolar disorder with hypersomnolence, and narcolepsy. Non-hypersomnolent comparison groups (n=30 in each group) will include: MDD without hypersomnolence, bipolar disorder without hypersomnolence, primary insomnia, and healthy controls.