Human brain tissues were obtained from the Wuhan brain bank in accordance with the brain bank protocol. Ethical agreements were obtained from the donors or their relatives by written informed consent. Total RNA was isolated from the frozen prefrontal cortex tissue using the Trizol (Invitrogen, USA) protocol with no modifications. Low molecular weight RNA was isolated, ligated to the adapters, amplified, and sequenced following the Small RNA preparation protocol (Illumina, USA) with no modifications.