Decreased 5-hydroxytryptamine in the brain may be caused by genetics, anxiety, depression, sleep disorders, and more. 5-hydroxytryptamine is an important neurotransmitter secreted by the brain and released by 5-hydroxytryptaminergic neurons in the reticular formation of the brainstem, which regulates mood, sleep and appetite. Large amounts of 5-hydroxytryptamine are released by 5-hydroxytryptaminergic neurons during wakefulness. And when anxiety, depression, sleep disorders can lead to a decrease in the release of 5-hydroxytryptamine from 5-hydroxytryptaminergic neurons. Genetic factors also play a key role in 5-hydroxy release. Decreased secretion of 5-hydroxytryptamine by the brain can lead to a variety of clinical symptoms, which should be promptly consulted with a professional neurologist for guidance in diagnosis and treatment.