Many clinicians and researchers who work with adolescents classify the adolescent problems into two general categories of difficulties: externalizing problems and internalizing problems. Externalizing problems are difficulties that affect the external world of adolescents, such as drug abuse, delinquency, and engaging in risky behaviors. The adolescent who is abusing drugs is likely to also be engaged in risky sexual behaviors and delinquency. The discovery of and experimentation with drugs are common for adolescents and vary primarily from socially acceptable and legal drugs such as caffeine, cigarettes, and alcohol to socially rejected and illegal drugs, ranging from marijuana to heroin and cocaine. Unfortunately, adolescents often do not think that drug abuse is harmful, despite the fact that both alcohol consumption and marijuana use have short-term and long-term negative effects. However, sexuality during adolescence has the potential to become a serious health concern.