Researchers identified three chemical phases of romance. Lust is driven by testosterone and estrogen — sex hormones creating initial physical attraction across all genders.

Attraction is the intoxicating early phase, powered by dopamine (euphoria), norepinephrine (racing heart, excitement), and lowered serotonin. The serotonin drop produces obsessive thinking — the same neurochemical pattern seen in OCD.

Attachment is the long-term bonding phase, sustained by oxytocin released during touch and vasopressin linked to protectiveness. This shift from dopamine to oxytocin explains why love changes character over time.