In the central nervous system, the neurotransmitter serotonin helps regulate mood, sleep, sexuality and appetite. It plays a part in many disorders, such as depression, migraine, bipolar disorder and anxiety.It also has an elegant shape that makes a stunning necklace sure to draw compliments. The sterling silver pendant is 1.5" wide and attached to a sterling cable with a lobster clasp, adjustable between 16 and 18 inches. This is also available with an 18" black rubber cord.It's packaged in a recycled gift box and an information tag about serotonin is included.