What is 'sad nipple syndrome', the trending term for sudden anguish or homesickness?

A Guardian lifestyle piece explains 'sad nipple syndrome', a term people are searching for to explain sudden bursts of anguish or homesickness. The items give no confirmed medical cause.

Timeline

1. 3 Nov, 17:00 UTCGuardian explains 'sad nipple syndrome'
2. 3 Nov, 17:00 UTCGuardian Lifestyle repeats the explainer

Top sources

• ‘The nipple touch of doom’: what is sad nipple syndrome and what causes it?The Guardian