Which of the following is a neurotransmitter in the brain that is responsible for maintaining mood balance and is related to depression?

Serotonin is a chemical created by the human body that works as a neurotransmitter. It is responsible for maintaining mood balance. An association is made between serotonin and depression. It is unclear if decreased levels of serotonin contribute to depression or depression causes a decrease in serotonin levels. Selective serotonin reuptake inhibitors (SSRIs) are a classification of antidepressants.