Quote of note:
...no sleep medication has been  approved for use in children under 18. Still, doctors commonly use medications  for patients and disorders for which the drugs have never received formal  approval, particularly when those patients are children. 
Sleeping Pill Use by Youths Soars, Study Says 
By GARDINER  HARRIS
The use of sleeping pills among children and very young adults rose 85  percent from 2000 to 2004, in yet another sign that parents and doctors are  increasingly turning to prescription medications to solve childhood health and  behavioral problems.
 And about 15 percent of people under age 20 who received sleeping pills were  also being given drugs to treat attention deficit and hyperactivity disorder,  according to the study by Medco Health Solutions, a managed-care company that  makes estimates about medication use in the whole population based on  extrapolations from its own data. Drugs used to treat attention disorders can  cause insomnia.
 Few of the prescriptions given to children and young adults have the approval  of the Food and Drug Administration because no sleep medication has been  approved for use in children under 18. Still, doctors commonly use medications  for patients and disorders for which the drugs have never received formal  approval, particularly when those patients are children.
 Dr. Robert Epstein, Medco's chief medical officer, said, "It leads you to  wonder whether these children are being treated for insomnia caused by  hyperactivity or whether the medication itself causes the insomnia."
 The use of sleeping medicines among adults doubled from 2000 to 2004, Medco  found.