5. Which drugs are the most addictive?

This is a difficult question to answer because it depends upon a lot of factors in both the drug and the person who uses it. In an attempt to define clearly what is meant by addiction, and which drugs are the most addictive, Dr. Jack E. Henningfield of the National Institute on Drug Abuse and Dr. Neal L. Benowitz of the University of California at San Francisco ranked six psychoactive substances on five criteria.

• Withdrawal -- The severity of withdrawal symptoms produced by stopping the use of the drug.
• Reinforcement -- The drug's tendency to induce users to take it again and again.
• Tolerance -- The user's need to have ever-increasing doses to get the same effect.
• Dependence -- The difficulty in quitting, or staying off the drug, the number of users who eventually become dependent
• Intoxication -- The degree of intoxication produced by the drug in typical use.

The tables listed below show the rankings given for each of the drugs. Overall, their evaluations for the drugs are very consistent. It is notable that marijuana ranks below caffeine in most addictive criteria, while alcohol and tobacco are near the top of the scale in many areas.

The rating scale is from 1 to 6. 1 denotes the drug with the strongest addictive tendencies, while 6 denotes the drug with the least addictive tendencies.

HENNINGFIELD RATINGS

Substance   Withdrawal   Reinforcement   Tolerance   Dependence  Intoxication
Nicotine         3             4             2           1            5

Heroin           2             2             1           2            2

Cocaine          4             1             4           3            3

Alcohol          1             3             3           4            1

Caffeine         5             6             5           5            6

Marijuana        6             5             6           6            4

BENOWITZ RATINGS

Substance   Withdrawal   Reinforcement   Tolerance   Dependence  Intoxication

Nicotine        3*             4             4           1            6

Heroin           2             2             2           2            2

Cocaine         3*             1             1           3            3

Alcohol          1             3             4           4            1

Caffeine         4             5             3           5            5

Marijuana        5             6             5           6            4

*equal ratings