Abstract: The present invention relates to a method for determining the degree of risk of onset of autism, comprising the step of measuring the triglyceride concentration or the cholesterol concentration in a very low-density lipoprotein fraction of plasma or serum isolated from a subject, or the triglyceride concentration or the cholesterol concentration of plasma or serum. In addition, the present invention provides a kit for determining the degree of risk of onset of autism and a method for screening for a candidate substance for agents for treating autism using a non-human mammal, in which the above described method is utilized.