This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Child Psychiatry, Subject name: Psychiatry
[{'content': 'In autism spectrum disorder, which of the following is identified as the first biomarker ? \nSelect and explain. \nA. Decreased brain volume in children less than 4 years, B. Reduced latency of sleep, C. Increased level of serotonin in the platelets, D. Increased levels of dopamine', 'role': 'user'}, {'content': 'Answer: C \nExplanation: In autism spectrum disorder, | level of serotonin in the platelets is identified as the first biomarker. Other biomarkers are mTOR pathway Increased total brain volume in children < 4 years of age g-aminobutyric acid (GABA) inhibitory system', 'role': 'assistant'}]