How can I tell if someone is using drugs?

Young people often have difficulty hiding their drug-induced dysfunction.  It is not unusual that one of the first signs of drug abuse is the need for more money. Behavioral changes may include increased secrecy, extreme mood swings, loss of interest in activities like sports or academics.   Tardiness and absences from school are also warning signs.  A change in friends is a red flag especially if the new friends are having behavioral problems.  Adults also will need more money and may exhibit similar behavioral symptoms. However, they are often better at hiding a drug problem for a longer period.