Why was Sun Guifei poisoned to be dumb?

Sun Guifei was speechless because she was afraid of getting mental illness.

Sun Guifei recovered slowly after being poisoned, but the medicine she was still taking was cured after being poisoned. Yao Ziliao became dumb because he helped Yin Ziping lie and ate hallucinogenic health food. It turned out that Yao Ziliao couldn't open her mouth because she was poisoned and hallucinated. Emperor Zhu Zhanji imprisoned Yao Ziling, and Yao Ziling thought of the past, not only out of fear of the queen mother, but also out of fear of being imprisoned, so Yao Ziling dared not speak.