ill at ease, distressed
忡 centers on a troubled inner state: feeling ill at ease or distressed, as if the heart is unsettled.
忡 combines the heart radical 忄 with 中, which likely contributes the sound. The character expresses a disturbed or uneasy heart.
The heart radical 忄 beside 中 suggests a heart that is struck in the middle, leaving it ill at ease and distressed.
For チュウ, imagine a distressed person chewing their lip nervously: chew -> チュウ, and the heart is uneasy.