Depends. This all depends on the child's specific situation. Some children do well on adhd meds, some do not. It is best to work with your pediatrician to try a combination of adhd drug trials and work with a mental health counselor or child psychiatrist to find a solution that works for you and your child.
Yes, for best result. If your child has been properly diagnosed with adhd, that means that he or she has a relative deficiency in certain neurotransmittors and the medicine helps restore the balance of these neurotransmittors so the brain can function optimally. You would not think of denying a person with low thyroid level of their thyroid medication, or a person with insulin-dependent diabetes of their insulin.