Normal controls and biological reference values in child psychiatry: defining normal.

About half of adults volunteering as normal control research subjects may be rejected because of significant psychopathology, but no parallel study has been done to date for pediatric subjects. Of 152 applicants (ages 6 to 18) for participation as paid normal controls, 44% were found ineligible and at least 31.8% of the child volunteers had probable or certain psychiatric disorders. Successive screenings, including rating scales and structured interviews, were necessary to obtain controls meeting a defined standard of psychiatric health. Careful scrutiny of child volunteers in biological psychiatric research is needed to assure meaningful comparisons.