Love most commonly refers to a feeling of strong attraction or emotional attachment. It can be impersonal (the love of an object, ideal, or strong political or spiritual connection) or interpersonal (love between two humans). Different forms of love have been described, including familial love (love for family), platonic love (love for friends), romantic love (sexual passion) and guest love (hospitality). Romantic love has been shown to elicit brain responses similar to an addiction. When in love dopamine, norepinephrine, serotonin and other chemicals stimulate the brain's pleasure center, leading to side effects such as increased heart rate, loss of appetite and sleep, and an intense feeling of excitement.