The phrase "become insane" refers to losing one's sanity and mental faculties. However, there are various synonyms that can be used to express the same idea, such as going crazy, becoming deranged, going mad, losing one's mind, or becoming unhinged. Other related expressions might include going off the rails, losing control, or experiencing a breakdown. While these words and phrases may have slightly different connotations and levels of severity, they all depict a state of mental instability and loss of rationality. It is important to note that mental health issues should be taken seriously and treated with the appropriate care and support.