Utilizing the chymotrypsin level of an individual as a measure of the success of secretin, other neuropeptides, and peptides or digestive enzyme in treating ADD, ADHD, Autism and other PDD related disorders. In one aspect, a method of determining the efficacy of secretin, other neuropeptides, peptides, or digestive enzymes for the treatment of an individual diagnosed with a pervasive development disorder (PDD) comprises obtaining a sample of feces from an individual, determining a quantitative level of chymotrypsin present in the sample, and correlating the quantitative level of chymotrypsin determined to be present in the sample with the PDD to determine the efficacy of treating the individual with secretin, other neuropeptides, peptides, or digestive enzyme administration.
METHODS FOR TREATING PERVASIVE DEVELOPMENT DISORDERS