adjective in a state of mind that prevents normal perception, behavior, or social interaction; seriously mentally ill : certifying patients as clinically insane | he had gone insane. • (of an action or quality) characterized or caused by madness : charging headlong in an insane frenzy | his eyes glowing with insane fury. • in a state of extreme annoyance or distraction : a fly whose buzzing had been driving me insane. • (of an action or policy) extremely foolish; irrational or illogical : she had an insane desire to giggle.
*One of the main symptoms of grieving, is feeling that you're loosing your mind.