Final answer:
Taking a drug for non-approved purposes or in a harmful manner is drug abuse. Abuse can lead to drug addiction, which is compulsive use despite adverse effects. Misuse can also lead to physical or psychological dependence.
Step-by-step explanation:
Taking a prescription or non-prescription drug for a purpose other than that for which it's medically approved or when it's detrimental to one's health/well-being is drug abuse. Drug abuse is the use of a drug without the advice of a medical professional and for reasons not originally intended. This type of use can often lead to drug addiction, which is the compulsive use of a substance such as a psychoactive drug despite negative consequences that such use may entail. Additionally, misuse of psychoactive drugs can lead to addiction and dependence, where the individual may experience withdrawal symptoms upon cessation of drug use. This can ultimately require professional intervention, such as rehabilitation, to overcome.