No! Not only is their the issue of a additive impact on neurogenesis, but the combination is potentially fatal as both depress brain stem activity. The brain stem takes care of a lot of basic functions, including the breathing and gag reflexes. In large doses the combo can lead to asphyxiation during sleep. Gag reflex suppression increases the risk of choking on vomit, or inhaling it into the lungs.
Quetiapine has a short half-life, around 6-7 hours, which makes it a better sleeping pill than mirtazapine because the sedation is less likely to continue into the next day. However, for depression, and especially anxiety, the trick is to maintain plasma levels as even as possible. Taking it in 2-3 split doses usually works well enough, but slow-release formulations are even better and only need to be taken once daily which increases compliance. Humans, being the ornery creatures we are, become progressively less interested in taking a med the more often we have to each day.I have also noticed I have immediate release quetiapine and everything I've read says it should be XR for adjunctive treatment of depression. Do you think that matters?