Medicaid and I485

First of all, thank gxu and sdfsdfsdff's reply about previous question.I have one more question. In our family only our son uses Medicaid and he is U.S. citizen. When we file I-485 in the future, should we answer "YES" about "have you received any public assistance from government, state, county?" or "NO". I am very confusing this question,since both of us never applied medicaid before. It's our son who receive public assistance (if medicaid is considered as " public assistance"). By the way, I was told Medicaid is not welfare program. Is that true? Please advise.
Thanks a lot in advance.