"Go loco" is a slang term usually associated with losing one's mind or going crazy. There are several synonyms that can be used to express similar sentiments such as "lose one's marbles," "flip out," "go bonkers," "go bananas," and "lose it." Other similar terms include "batty," "nuts," and "wacky." These words can be used in various contexts, such as when someone is behaving erratically, acting irrationally, or experiencing a mental breakdown. While these terms may sound humorous or playful, it is important to remember that mental health is a serious issue, and those struggling with mental illness should be treated with kindness and empathy.