The Drug Enforcement Administration told makers of medication for attention-deficit hyperactivity disorder that it was concerned that “aggressive marketing practices” by companies including telehealth providers could be driving excessive prescriptions, according to a letter from the agency. While the letter doesn’t cite specific companies, it reflects the DEA’s concerns about marketing efforts for ADHD treatment by telehealth companies such as Cerebral Inc. and Done Global Inc., whose prescribing practices the agency has been investigating.