The invention provides a method of prognosis for applied behavioural analysis treatment of mental disease, in particular autism or cerebral palsy, in a human subject, said method comprising analyzing a sample of body tissue or fluid from said subject for the presence or absence of a chemical marker indicative of the likelihood of success or failure of applied behavioural analysis treatment of said mental disease, and optionally, based on said analysis, beginning, continuing or ceasing applied behavioural analysis treatment of said subject. The sample is preferably an urine sample, and the preferred prognostic markers are: gluten derivatives, indolyl-3-acryloylglycine (IAG) , serotonin uptake stimulator, ??-casomorphineamides, gliadinomorphine, ??-casomorphines, deltorphins, Demorphine, glutemorphine , gluten exophins, compounds of molecular weight of 687 Daltons.
