发疯 is deeper than 抓狂。and 发疯 is bad ,to other people but 抓狂 is to myself

Hello Beth, I just read the answers above and found they didn't hit the nail on the head. Normally they are interchangable, for example 楼市让人发疯，让人抓狂 The property market drives us crazy. However 抓狂 implies that there is nothing you can do about it when bad things happen, or you are in a situation that goes beyond your ability or experience to handle it. in this sense, 抓狂 can't be replaced with 发疯。in addition, 抓狂 foucus on inner feelings and 发疯 is more of outer behavior 每次客人来，我小孩就发疯 My kids act up whenever guests come.　（outer behavior: they behave badly by being very active and noisy or throwing tantrums ） 每次摆不好拼图，我小孩就抓狂 My kid goes crazy whenever he fail to solve his jigsaw puzzle (inner feelings: He feels irritated or angry ) 发疯 literally means someone who is mad or insane is seriously mentally ill so that they cannot live in normal society, in this sense, they are not interchangeable, we can't use 抓狂here.

"抓狂" 其實是臺灣閩南語詞彙 " 掠狂 lia̍h-kông " 被誤寫後 又滲入華語(國語)的詞彙 "掠"在台灣閩南語裡頭 正是 "抓" 的意思 "掠龜走鱉" 抓到龜 鱉卻跑掉了 顧此失彼之意 "掠猴" = "掠姦" 抓姦之意 (猴似人 卻無人倫道德 通姦之人即是猴) "掠狂" 通常表示極為憤怒或極度緊張。

事实证明，不同的人对抓狂有不同的理解，现今生活中，抓狂已不再限于它的原意，甚至也不再限于字典上的意义。语言的发展变化使这个词被赋予了更多的意义，就连手忙脚乱也有人用“抓狂”来形容，读者能看懂，而且也没有人觉得不妥。

"每次摆不好拼图，我小孩就抓狂" 台灣閩南語應該不會如此表達 "抓狂是鬱積已久 而突然爆發的失控情緒與行為 這種情緒與行為是因為外在的人 事 物所激發的" 拼不好圖罕用"抓狂" 來形容自發的行為 這個閩南語詞彙不但被誤寫 詞意也因為輾轉使用而稍稍背離了原意 "掠狂"和閩南語的 "起痟" (華語 "發瘋") 詞意上還有一段差距