Taking mirtazapine for 6 years of poor sleep may be due to inappropriate drug dosage and individual variability. 1. Inappropriate drug dosage: the recommended dosage of mirtazapine for the treatment of insomnia is 0.5 to 1 tablet, if you take a smaller dosage, the effect of the drug will be weaker, and if you take a larger dosage there will be excessive sedation. 2. Individual variability: after long-term use of mirtazapine sensitivity to the drug decreased, at first able to fall asleep, after taking 6 years of drug tolerance, resulting in taking sleep, without any sleep aid. At this time, you can consider changing the drug and using other sedative-hypnotic drugs, such as oxazepam and zopiclone. Common side effects of Mirtazapine include weight gain, drowsiness, sedation, and increased appetite. It is contraindicated in case of allergy to the drug, pregnant and lactating women. The drug should be used under the supervision of a physician.