Pop star Robert Palmer was right when he sang about being "Addicted to Love".
Scientists have traced the origin of love to a part of the brain linked to drug addiction.
It forms a habit out of pleasurable feelings of sexual desire that no one wants to break.
The same mechanism compels the drug addict to keep seeking another "hit" from heroin or cocaine.
Scientists drew a map of love and desire in the brain by looking at what happens when people view erotic pictures or photos of their partners and spouses.
Data pooled from 20 different studies revealed that two brain structures, the insula and striatum, play key roles in sexual desire and love.
Both activated different areas of the striatum, a region located deep in the cerebral cortex.
Sexual desire stimulated the same "reward" neurons as those which respond to anything inherently pleasurable, such as sex and food.
The "love area", meanwhile, was involved in a more complex conditioning process that drives the need to repeat high value reward sensations.
Psychologist and study leader Professor Jim Pfaus, from Concordia University in Montreal, Canada, said: "Love is actually a habit that is formed from sexual desire as desire is rewarded. It works the same way in the brain as when people become addicted to drugs.
"While sexual desire has a very specific goal, love is more abstract and complex, so it's less dependent on the physical presence of someone else."
The research is published in the Journal of Sexual Medicine.
Love was not necessarily a bad habit, activating many brain pathways involved in pair bonding and monogamy, said Pfaus.
But much of what made love a many splendoured thing remained a mystery to science.
Pfaus added: "I see this paper as a cornerstone in what I hope will turn into more studies in human social neuroscience that can give us an idea of where love is in the brain."