An indicator is something the patient feels and explains while a clue is something that others like doctor or friends see in the patient. Example is the case of dilated pupils being a sign while constant sleepiness is a symptom.
Drug Addiction - an addicted person cannot resist or restrict himself to the intake of the substance be it drug, alcohol, cigarette. They keep taking it, despite the fact that it might bring about mischief (the individual could conceivably know about the potential damage).
Being dependant on a substance can lead to strong cravings. It will be extremely difficult for the addict to stop using the substance without external assistance, even when they want to.
The clues and indicators that someone is addicted differ from one person to the other, depend on the drug, the genes of the individual and status in life.
Some of the symptoms and signs of drug dependence can include:
Certain alcohol or substance abusers who aren't technically addicted might also be affected by or cause a few of the above-mentioned descriptions, though these abusers don't generally experience the withdrawal symptoms of addicts or the exact same obsession to use the substance.