Mirtazapine, a tetracyclic antidepressant, is effective in the treatment of depression. The main antidepressant effect is by blocking the adrenergic receptors in the presynaptic membrane, leading to an increase in norepinephrine release. It also stimulates 5-hydroxytryptaminergic neurons, allowing for an increase in 5-hydroxytryptamine release, which ultimately exerts an antidepressant effect through an increase in norepinephrine and 5-hydroxytryptamine neurotransmitters. This class of antidepressants has a very good effect in treating depression, but also has certain side effects, such as drowsiness and excessive sedation. It is also possible to have an increased appetite if taken for a long period of time. If the appetite increases and activity decreases, you will soon gain weight or even develop diabetes or metabolic disorders. If you are taking mirtazapine for the treatment of depression, it is especially suitable for patients with depression accompanied by anxiety, mood, and insomnia. However, it is important to pay attention to side effects such as weight gain, increased appetite, and drowsiness while taking the medication.