Onset of action appears faster than some selective serotonin reuptake inhibitors (SSRI) and similar to tricyclic antidepressants.In 2010, NICE recommended generic SSRIs as first line choices, as they are "equally effective as other antidepressants and have a favourable risk–benefit ratio." With respect to mirtazapine, it found: "There is no difference between mirtazapine and other antidepressants on any efficacy measure, although in terms of achieving remission mirtazapine appears to have a statistical though not clinical advantage. In addition, mirtazapine has a statistical advantage over selective serotonin reuptake inhibitors in terms of reducing symptoms of depression, but the difference is not clinically significant. However, there is strong evidence that patients taking mirtazapine are less likely to leave treatment early because of side effects, although this is not the case for patients reporting side effects or leaving treatment early for any reason. "A 2011 Cochrane review that compared mirtazapine to other antidepressants found that, while it appears to have a faster onset in people for whom it works (measured at two weeks), its efficacy is about the same as other antidepressants after six weeks use.A 2012 review focused on antidepressants and sleep found that in many people with sleep disorders caused by depression, mirtazapine reduces the time it takes to fall asleep and increases the quality of sleep, but that in some people it can disturb sleep, especially at higher doses, causing restless leg syndrome in 8 to 28% of people and in rare cases causes REM sleep behavior disorder.
Mirtazapine, sold under the brand name Remeron amongst others, is an atypical antidepressant, and as such is used primarily to treat depression. Its effects may take up to four weeks, but can also manifest as early as one to two weeks. It is often used in cases of depression complicated by anxiety or insomnia. The effectiveness of Mirtazapine is comparable to other commonly prescribed antidepressants. It is taken by mouth.Common side effects include sleepiness, dizziness, increased appetite and weight gain. Serious side effects may include mania,  low white blood cell count, and increased suicide among children. Withdrawal symptoms may occur with stopping. It is not recommended together with an MAO inhibitor, although evidence supporting the danger of this combination has been refuted. It is unclear if use during pregnancy is safe. How it works is not clear, but it may involve blocking certain adrenergic and serotonin receptors. Chemically, it is a tetracyclic antidepressant (TeCA), and is closely related to mianserin. It also has strong antihistaminergic effects.Mirtazapine came into medical use in the United States in 1996. The patent expired in 2004, and generic versions are available. In 2019, it was the 106th most commonly prescribed medication in the United States, with more than 6 million prescriptions. Medical uses
Depression
Mirtazapine is primarily used for major depressive disorder and other mood disorders.