Serotonin is a neurotransmitter that plays a role in mood. It is important for reducing depression and regulating anxiety. It also regulates digestion, sleep, and bone health.

Oxytocin is also called the "love" hormone and is associated with how people bond and trust one another. It explains why you feel happy to cuddle with your pets. It also helps parents bond with their newborn.

Endorphines are linked with exercise. They function as natural painkillers that help minimize pain and maximize pleasure, explaining why an athlete may be able to push through a race with an injury that they don't notice until later.

There are four main hormones that trigger the feelings of happiness: dopamine, serotonin, oxytocin, and endorphins.