For sleep across the board, Seroquel is really good overall for me. Every now and then, I'd experience mixed mania and stop sleeping, but the only reason for that, is because I should have been on a higher dose at the time.

200 mg and lower did not have enough anti-manic or antidepressant properties, although it would sometimes help a bit with anxiety due to its sedating properties. 600+ mg worked as an anti-manic (for bringing me down from acute episodes) and helped treat mixed episodes with other meds, but caused side effects. The benefits do outweigh the risks at times, temporarily. 300-400 mg is a good maintenance range for me for help with insomnia, anxiety, depression with the help of other meds. It's my goal to stay off of high dose Seroquel, since it caused side effects. Good luck.