In [TGH: 40, Damane, 484], Egwene's sul'dam describes how the Empress will sometimes make a man wear the bracelet of the a'dam connected to a damane. Sometimes nothing happens, and sometimes "both die, screaming." We see something similar happen in [TFOH: 32, A Short Spear, 370] when Rand tries to free the damane in Seanchan. A third example is in [ACOS: 8, The Figurehead, 164], when Aran'gar frees Moggy from the a'dam while Egwene is wearing the bracelet: "A sudden stab of pain through that pocket of sensations in the back of her head.... Had she felt it directly, it would have been numbing. As it was, her eyes bulged in shock. A man who could channel was touching the necklace around Moghedien's neck; this was one link no man could be brought into."
What's happening here? Well, it seems as if the men who are affected by the a'dam are those who can channel, or maybe who have the ability to learn. According to Elayne's study of the a'dam, it works by creating an uneven link between channelers, in which the bracelet holder has complete control. So possible explanations for the "die screaming" effect are: