Shake it off?

Rejected by a person you like? Just “shake it off” and move on, as music star Taylor Swift says.

But while that might work for many people, it may not be so easy for those with untreated depression, a new brain study finds.

The pain of social rejection lasts longer for them — and their brain cells release less of a natural pain and stress-reducing chemical called natural opioids, researchers report in the journal Molecular Psychiatry.

The findings were made in depressed and non-depressed people using specialized brain-scanning technology and a simulated online dating scenario. The research sheds new light on how the brain’s pain-response mechanism, called the opioid system, differs in people with depression.

On the flip side, when someone they’re interested in likes them back, depressed people do feel relatively better — but only momentarily. This may also be explained by differences in their opioid system compared to non-depressed people, according to the new results.

Further research could lead to a better understanding of how to boost the opioid response in depressed individuals to reduce the exaggerated effect of social stress, and to increase the benefits of positive social interactions.