It is commonly thought that addiction is the result of a lack of will power, however, the disease theory of addiction does not support this argument. It posits that addiction is not simply a lack of willpower. The theory, however, has some limitations.
A general question arises that why different people are affected differently by drugs of addition. Some people are heavily addiction by substance of abuse, while others are not affected at all.
According to the Canadian psychologist, Bruce K. Alexander, most of the drug users become addicted, and that the addiction is caused by exposure to the drugs no matter what quantity they use. Thus, according to him, people who use even a smaller quantity of drugs, become addicted to it. B.K. Alexander further argues that his claims have not been backed by scientific evidence. For example, opiate consumption was more common in Europe and United States during the 19th century than it is now but less than 1% of the population became addicted and the numbers were declining at the end of the century. Another example is from the United Kingdom where in 1972, physicians were prescribing drugs including heroin as a treatment for certain diseases such as cough, chronic pain and diarrhea, yet, the researcher in the U.K found that very low number of people became addicted to heroin.
Thus, these findings challenges the disease theory.