The objective of this study is to gain preliminary information and knowledge on metabolic profile in ASD. The benefit of this study will be to expand our insight of the potential relationship in metabolic processes and neuropsychological functions in ASD. For example, based on the obtained data of the study we can determine whether there is a link between the tryptophan pathway and cognitive functions in autism. The project is based on a systematic and multidisciplinary approach using tracers for delineating the mechanism by which the metabolism of amino acids like TRP is involved in affective and cognitive functions in ASD. Using an innovative approach to the evaluation of amino acids has not been used in adults with ASD. In addition, the obtained data of the study holds promise to develop specific markers (metabolic and/or neuropsychological) for guiding the identification those individuals with increased risk of developing mood disturbances or cognitive impairment, and for predicting the therapeutic effect of a specific nutritional interventions in subjects with ASD.