mental illness (countable and uncountable, plural mental illnesses)
- (uncountable, psychiatry) The property of being mentally ill; mental disorders taken as a whole.
2006, R. Keith Sawyer, Explaining Creativity: The Science of Human Innovation, Oxford University Press US, →ISBN, page 87:
Such studies show that geniuses are not any more likely to suffer from mental illness than the rest of us.
- (countable, psychiatry) A mental disorder.
2002, Vikram Patel, Where There is No Psychiatrist: A Mental Health Care Manual, RCPsych Publications, →ISBN, page 70:
Epilepsy is not a mental illness. It is caused by electrical changes in the brain.
mental disorder (countable)