"Legalization of more drugs, such as marijuana, will lead to more addiction"

Earlier today, I posted an excerpt from the Reality-Based Community blog about the high-potency marijuana that would dominate a legal market.  In their post, they include a link to an article called, "The changing face of American addictions".  The article includes an interview with Psychologist and addictions researcher Keith Humphreys, PhD.  He expresses concern that legalizing more drugs, including marijuana, will increase drug addiction rates in our country.  Here is an excerpt from the interview:

Q: In your view, are some addictions more harmful than others, and what are they?

A: In terms of damage to population health, the deadliest addictions are to alcohol and tobacco, because they are legal, and therefore, easy to access, inexpensive, skillfully marketed and widely available.

Children and adolescents are the group that suffers the most from addictive drugs, for two reasons. First, because their brains are still developing, they are particularly likely to become addicted when they use. You hardly ever, for example, meet an addicted smoker who didn't start smoking as a teenager. Second, unlike someone with an addicted boyfriend or sibling or friend, children don't have the power to escape an addicted parent. They may therefore endure years of coping with the addiction and with the emotional and physical abuse that their addicted parent dishes out.

Q: What measures would help reduce addictive behavior in the U.S.?

A: Higher taxes on alcohol, increased restrictions on the advertising of tobacco products, more careful prescribing of pain medication by doctors, and greater availability of addiction treatment would all be helpful. Some progress has been made on all these fronts, but the basic political problem is that when a drug is legal (e.g., tobacco, alcohol, prescription pain medication), it is hard to regulate. Industries that sell the products make large campaign contributions and hire armies of lobbyists which keep taxes and regulation on their products as minimal as possible. That's a key reason why the legalization of more drugs, such as marijuana, will lead to more addiction.