Wiktionary
n. an attack of depression or anxiety so severe that it prevents a person from continuing to function normally
Wikipedia
Mental breakdown (also known as a nervous breakdown) is a general term for an acute, time-limited mental disorder that manifests primarily as severe stress-induced depression, anxiety, or dissociation in a previously functional individual, to the extent that they are no longer able to function on a day-to-day basis until the disorder is resolved. A nervous breakdown is defined by its temporary nature, and often closely tied to psychological burnout, severe overwork, sleep deprivation, and similar stressors, which may combine to temporarily overwhelm an individual with otherwise sound mental functions.
Usage examples of "mental breakdown".
An alleged psychiatric case or mental breakdown patient, who is sick of both the war and the sea, would make an ideal choice for the traitor's part and I shouldn't even imagine that the price would have to be very high.
He simply assumed it was another symptom of his continuing mental breakdown.
Adrenalin therapy might stave of a mental breakdown, but it most assuredly would hasten a physical breakdown.
She agreed that it could be hallucinogens but said that the possibility of some kind of mental breakdown shouldn't be overlooked.
Was it just possible that under the immense burden of all mankind's problems the machine was capable of having a mental breakdown?
Hardly, he felt, the most conductive setting to try to explain to her as she sat there, suddenly cool and defensive, that in a sort of out-of-body dream he had had a telepathic sense that the mental breakdown she had suffered had been connected with the fact that, appearances to the contrary nonwithstanding, the Earth had been demolished to make way for a new hyperspace bypass, something which he alone on Earth knew anything about, having virtually witnessed it from a Vogon spaceship, and that furthermore both his body and soul ached for her unbearably and he needed to got to bed with her as soon as was humanly possible.