Board Thread:General Discussion/@comment-25877059-20150630023513/@comment-5780397-20150704095045

Being so strictly linked to one's mind, Nen is most likely affected by the placebo/ocebo effect: as you said, an example is given by the concept of Vows & Limitations, but we also saw how a character's strength varies depending on their mental strength. For instance, Killua's power was greatly reduced when Illumi was conditioning him, and Kastro is unable to control his ability properly when the mental pressure is too great. Also, Gon's aura spikes according to his emotions. I think that Conjuration, which could be really described as the physical manifestation of one's fantasy and the closest thing to reality manipulation, is the category that is affected by one's mind the most, and thus by the placebo/nocebo effect.