Abused Drugs

Most common substance of use in India: Tobacco 
Most common substance of use in world: Alcohol 
Most common substance of use in western countries:Alcohol 
Most common illicit substance of use in India: Cannabis 
Most common illicit substance of us in world:Cannabis
Most common illicit substance of use in western countries: Cannabis 

Now coming to abuse, remember although DSM IV TR DOES NOT RECOGNISE TOBACCO AS SUBSTANCE OF USE but nearly 70-80% of those who use it; use in dependent pattern, now dependence is more higher criteria than abuse 
The hallmark book on substance abuse includes tobacco in it(Substance Abuse: A Comprehensive Textbook; Fourth Edition by Joyce H. Lowinson 
;Substance Abuse: A Comprehensive Textbook focus on addiction in children, adolescents, adults, and the elderly and women's health issues, including pregnancy) 

Most common substance of abuse 

Most common substance of abuse in INDIA: Tobacco 
Most common substance of abuse in world: Tobacco (All Alcohol users do not use in abuse pattern; about 80% are social drinkers, 10%abuse, 105 dependent of all who use alcohol) 
Most common substance of abuse in western countries:Alcohol 
Most common substance of abuse in India as per DSM-IV TR: Alcohol 
Most common substance of abuse in world as per DSM IV TR: Tobacco 
Most common substance of use in western countries as per DSM IV TR: Alcohol 
Most common illicit substance of use in India: Cannabis 
Most common illicit substance of use in world:Cannabis 
Most common illicit substance of use in western countries: Cannabis 

India: Substance use 
Tobacco- 52% 
Alcohol- 21.4% 
Cannabis- 3% 
Opium- 0.4

Courtesy: Dr.Yatin Talwar