Operational Definition: Drug dependence - The repeated use of a drug or chemical substance, with or without physical dependence. Behavioural dependence involves drug-seeking activities and related evidence of pathological use patterns, whereas physical dependence refers to the physical (physiological) effects of multiple episodes of substance abuse. Psychological dependence also referred to as habituation, is characterized by a continuous or intermittent craving (i.e., intense desire) for the substance to avoid a dysphoric state. Behavioural, physical and psychological dependence are the hallmark of substance use disorders. Physical dependence indicates an altered physiologic state caused by repeated administration of a drug, the cessation of which results in a specific syndrome Drug Abuse and Dependence - Abuse is the first category that describes patterns associated with maladaptive patterns of substance use. According to DSM-IV (American Psychiatric Association, 1993), abuse is indicated by a continued use (at least 1 month) despite the knowledge of having persistent or recurring problems associated with the drug, or recurrent use in situations in which that use is physically hazardous. The most commonly followed diagnostic system is that published by WHO, the ICD10 (International Classification of Diseases). ICD 10 classifies Substance Use Disorder into intoxication, harmful use, dependence syndrome, withdrawal state, psychotic disorder and amnestic syndrome. Dependence syndrome has been defined in ICD10 as "A cluster of physiological, behavioural and cognitive phenomena in which use of a substance or a class of substances takes on a much higher priority for a given individual than other behaviours that once had greater value". The ICD 10 criteria specify dependence as three or more experiences exhibited at some time during a one-year period: a) Tolerance: there is a need for significantly increased amounts of the substance to achieve intoxication or the desired effect, or a markedly diminished effect with continued use of the same amount of the substance. b) Physiological withdrawal state: characteristic symptoms experienced on,