What drives poverty?

I read Bryan Caplan's blog everyday. If you have not read his book on the selfish reasons to have more kids, you should. In a recent post he writes:  

Why are the poor more likely to abuse drugs and alcohol? As a matter of dollars and cents, substance abuse should rise, not fall, with income. These habits are expensive, both directly and indirectly. Directly: Drugs and alcohol cost money. Indirectly: Drug and alcohol abuse make you less employable, less healthy, more reckless, and more likely to get in trouble with the law.  

First-hand accounts of poverty generally recognize that heavy users of drugs and alcohol pay a high material cost. Yet they rarely reach my verdict: that other factors - like low IQ, low conscientiousness, low patience, or plain irrationality - must be driving both poverty and substance abuse. Instead, observers usually say that the poor consume drugs and alcohol to "dull the pain." Some even argue that the poor are being entirely rational: If your life is a living hell, narcoticizing yourself is the simplest solution. 

There's just one problem with this explanation: By almost all accounts, substance abuse eventually makes your life worse. The long-term addict's life is utterly wretched - even if you average in his periodic drug-induced euphorias. Someone who has yet to start using drugs and alcohol doesn't face a choice between "full pain" and "dulled pain." Instead, he chooses between two paths of pain: 

Path #1: Full pain in the short-run, followed by gradual life progress. 

Path #2: Dulled pain in the short-run, followed by a gradual downward spiral into abject misery. 

Suppose you're poor. Your life is unusually painful, so the immediate effect of drugs and alcohol is especially attractive. The long-run prognosis for a poor substance abuser, however, is especially repellent. You hit "rock bottom" sooner because you don't have far to fall. And your version of "rock bottom" is extra bleak because you lack the financial resources and social connections to cushion the blow and get back on your feet. 

The lesson: On net, poverty isn't a believable root cause of substance abuse, because being poor doesn't make substance abuse a better overall deal. Why then would poor people be more inclined to narcoticize themselves? Once again, we should look for root causes of poverty and pathology. Low patience is the most obvious suspect. If you loathe to defer gratification, you'll tend to have low income, and eagerly use drugs and alcohol today despite their awful cost down the line.  

Closing questions: If you were poor, would you turn to drugs and alcohol? If you were a social worker, would you advise the poor to turn to drugs and alcohol? I doubt it. The reason, of course, is that on some level you already know what I'm telling you: Poverty is no excuse for substance abuse because substance abuse is an absurd response to poverty.

There are many ideas in this post, with a lot of repercussions. One of them is: for individuals who were poor and became rich their IQ, patience, conscientiousness, or/and level of rationality, among others, changed. One of the challenges is therefore to understand what drives changes in IQ, etc.