He's so paranoid that his coworkers are plotting against him that it's hard to work with him.

paranoid 是形容词，来自名词 paranoia（偏执狂、妄想症），指"过度猜疑、不信任他人"的心理状态。这个词常用来形容毫无根据地认为别人要伤害或欺骗自己的病态心理。