[Sadrain]

It is disturbances in vegetative nerve system, it often appears as stress, unreasonable fears (like, from going out of the house or going somewhere that has caused lot of stress), strong pains without seeming reason, head spinning to the border of fainting, fewer and other random sickness symptoms, even if there is no apparent reason for them to show up. From it, later real sicknesses can develop. Some call it as the next stage from a long lasting depression.
Basically, it is body rebelling against you going trough stressful situation and trying to force you to go in a relaxing state by avoiding any stress, like you can't leave the house and go to the school where you are constantly bullied...