A sign is something others, like the doctor, see, whilst a symptom is something that the patient discerns and explains. 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. Even if the substance poses a danger, they will still take it whether or not they know the dangers.
Drug addiction makes the body have a strong desire for the substance. It will be extremely difficult for the addict to stop using the substance without external assistance, even when they want to.
Personal circumstances, genetics, and the specific substance being used are all things that can determine how the signs and symptoms of abuse will manifest in an individual.
Signs and symptoms of substance enslavement may include:
Some people who abuse drugs or alcohol might not be technically addicted but can still suffer the effects mentioned here but do not usually suffer from withdrawal symptoms or have the same obsession to use the substance.