A director of a Chiba hospital has been questioned by police on suspicion that she supplied her son with a government controlled drug to help him study and prepare for a dentist license exam, it was learned April 8.

The 71-year-old chief of a pediatrics hospital in Yachimata, Chiba Prefecture, gave about 500 tablets of the psychoanaleptic Ritalin, which has a stimulant effect, to her 36-year-old son last October, according to regional drug control officials of the Health and Welfare Ministry.

The names of the doctor and her son were not provided. The mother has admitted the wrongdoing, saying she wanted to help her son concentrate on his studies. The son has reportedly confessed that he has been receiving the drug from his mother since he was in high school.

The son was arrested in February for possession of the drug. Investigators at the office have questioned him to learn where he obtained the large quantities of the drug they seized from his home.

Ritalin is often used to treat mental disorders such as depression. A 1992 revision of the Stimulant Drugs Control Law bans usage of the drug except for purposes of treatment.