Thanks for the good answer. The term "clinical depression was described though its causes are not properly clarified. You used "level of seratonin in the brain" but the term "seratonin" is misspelled. The term must be "serotonin" which refers to an organic compound, C 10 H 12 N 2 0, which can be found in the brain, blood serum, etc. and active as a neurotransmitter and in vasoconstriction, stimulation of the smooth muscles, and regulation of cyclic body processes. But its a typographical error

Your typographical error does not affect the essence of your answer, which is still running for the "best answer." .