It is often said that love is a drug.

But romance really does work in a similar way to addiction to illegal substances – it triggers a reaction in the same part of the brain, scientists have revealed.

Those smitten will produce an emotional response in the part of the grey matter normally involved with motivation and reward.

Our brains have been hardwired to choose a mate, and we become so motivated to win them over that we are sometimes willing to go to extreme lengths.

Addictive: Love produces the same pleasure and anxiety as drugs

Addictive: Love produces the same pleasure and anxiety as drugs

The reward comes from recognising that something feels good and is worth the effort.

‘You can feel happy when you're in love, but you can also feel anxious,’ said Lucy Brown, a neuroscientist at Albert Einstein College of Medicine in New York.

Professor Brown said that the reward part of the brain – or  pleasure centre - is an essential  to our survival as this drives the need to have sex.

Co-author Arthur Aron, a psychologist at the State University of New York at Stony Brook, said: ‘Intense passionate love uses the same system in the brain that gets activated when a person is addicted to drugs.’

Their study looked at magnetic resonance images of the brains of 10 women and seven men who claimed to be deeply in love.

The length of their relationships ranged from one month to less than two years.

Participants were shown photographs of their beloved, and photos of a similar-looking person.

Pleasure centre: The same part of the brain responds to romance and drugs

Pleasure centre: The same part of the brain responds to romance and drugs

It revealed that romantic love is one of the most powerful emotions a person can have.

They also found that the length of time couples were together made little difference to the intensity of their feelings.

The researchers discovered that in each of these long-term lovers, brain regions were also activated when they looked at photos of their partners.

Long-term love showed activity in the regions linked with attachment and liking a reward.

‘For most people, the standard pattern is a slow decline in passionate love but a growth in bonding,’ Dr Aron said.

That bonding allows for the partners to stay together long enough to have and raise children.

But with the decline in passionate means a decrease in anxiety.

‘As long as love remains, we get used to the relationship, and we're not afraid our partner will leave us, so we're not as focused on the craving,’ Dr Aron said.