Chemical Imbalance Meaning

(euphemistic) Mental illness.

Example: Used other than as an idiom: see chemical,‎ imbalance.
Warden, Rob and Drizin, Steven (2009) True Stories of False Confessions, ISBN 0810126036: “Anyone who knew him well would suspect he had a chemical imbalance. He had been unhappy recently. And there was a history of suicide in the family; his mother had tried to kill herself.”