What is love, according to science?

Anthropologist Helen Fisher proposed that love involves three overlapping systems: lust, fuelled by sex hormones; attraction, linked to dopamine and norepinephrine; and long-term attachment, supported by oxytocin and vasopressin. Brain scans of people newly in love, published in 2005, showed strong activity in reward regions such as the ventral tegmental area, the same circuits activated by addictive drugs. A 1999 Italian study found that serotonin levels in people newly in love dropped to levels similar to those seen in obsessive-compulsive disorder, which may explain constant thoughts about a partner. The intense early phase usually calms within a few years, giving way to deeper attachment. The long-running Harvard Study of Adult Development has found close relationships are among the strongest predictors of health and happiness.