Nervous Breakdown - It was also called "nervous prostration" a condition of irritable weakness. Today people who have anxiety disorders, depression, and/or bipolar disorder would all fall under the rubric of "nervous breakdown."
In the USA, from about the early 1900's until about the early 1970's, the term 'nervous breakdown' was very uncomplimentary in its use. Similarly, terms were used for the person such as, 'freaked out' or became a "wacko" or "nuts."
We know in mental illnesses, neurotransmitters and other aspects of the central nervous system are out of sync and result in all kinds of mental and bodily symptoms. The term continues to persist and in my opinion should be taken out of the English language.{Please see Broken Minds Hope for Healing When You Feel Like You’re Losing It by Steve and Robyn Bloem, (c 2005) Grand Rapids, Kregel chapter 2 "Stress and the Gathering Storm, pp. 27-35.