Quetiapine is commonly used to treat major depression and insomnia, although there is a commonly held view that sedation underlies its antidepressant effect. Unlike most antidepressants that bind to one or two receptor sites, quetiapine has a broad mechanism of action and binds to over a dozen neurotransmitter receptors, with varying affinities, at clinically relevant doses. Because of this, quetiapine has the ability to produce different effects at different doses, in which the relative occupancy at neurotransmitter receptor sites is changes accordingly. This is evidenced by the broad dosage range for quetiapine that varies based on the disorder being treated (e.g., higher doses for schizophrenia than major depression).