The basic ideal of the lightweavers (Nahal bond with a cryptic) seems to encourage insanity, even from before the bond. Elhokar and Shallan began by seeing shadowy figures everywhere, surrounding them (the cryptics). Then they have to tell a deep truth to advance in the ideals. This truth (if Shallan is an example) is something the the lightweaver hasn't dealt with. During the third part of OB, when Shallan stabbed herself to see the pain spren, Pattern became increasingly upset.
Was self harm a common problem with lightweavers? Shallan already has a borderline split personality, is it common for lightweavers to have other "problems"?
Just general curiosity here.