Researchers from the University of Colorado Boulder in the US study that measured the neurological and behavioural impacts the placebo effect had on a group of recently broken- hearted volunteers.
"Breaking up with a partner is one of the most emotionally negative experiences a person can have, and it can be an important trigger for developing psychological problems," said postdoctoral researcher Leonie Koban.
Such social pain is associated with a 20-fold higher risk of developing depression in the coming year, researchers said.
For decades, research has shown that placebos - sham treatments with no active ingredients - can measurably ease pain, Parkinson's disease and other physical ailments.
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The study is the first to measure placebos' impact on emotional pain from romantic rejection.
Researchers recruited 40 volunteers who had experienced an "unwanted romantic breakup" in the past six months.
They were asked to bring a photo of their ex and a photo of a same-gendered good friend to a brain-imaging lab.
Inside a functional magnetic resonance imaging (fMRI) machine, the participants were shown images of their former partner and asked to recall the breakup.
As these stimuli were alternately repeated, the subjects rated how they felt on a scale of 1 (very bad) to 5 (very good). The fMRI machine tracked their brain activity.
While not identical, the regions that lit up during physical and emotional pain were similar.
The subjects were then taken out of the machine and given a nasal spray. Half were told it was a "powerful analgesic effective in reducing emotional pain." Half were told it was a simple saline solution.
Activity in the brain's dorsolateral prefrontal cortex - an area involved with modulating emotions - increased sharply. Across the brain, areas associated with rejection quieted.
Notably, after the placebo, when participants felt the best they also showed increased activity in an area of the midbrain called the periaqueductal grey (PAG) which plays a key role in modulating levels of painkilling brain chemicals, or opioids, and feel-good neurotransmitters like dopamine.
"If you've been dumped recently, doing anything that you believe will help you feel better will probably help you feel better," Koban said.