Immigration is almost always discussed in terms of its impact upon the host country. This is, of course, only a part of the story. There's also the question: what does immigration do to the migrant himself?

The answer is: not all good. A new paper by Alan Barrett and Irene Mosca has found that alcohol abuse is far more prevalent amongst older Irishmen who had spent time living overseas than it is amongst men who had never migrated. For men over 50, 15% of those who had spent one to nine years living overseas have a drink problem - twice the prevalence among men who never migrated.

In itself, these numbers aren't conclusive. People who have migrated are more likely to have been sexually or physically abused as a child, and it could be this abuse that is a common cause both of their migration and their drink problem. But Barrett and Mosca find that, even controlling for this - among other things - migrants are still more likely to have alcohol trouble.

Alternatively, it could be that migrants who have returned to Ireland are those that failed to settle, and this failure explains their trouble. But this is not so. Irishmen who stay in England are also more likely to be heavy drinkers than Irishmen who never migrated; the maudlin Irish drunk used to be a staple figure in North London pubs, and maybe still is.

Instead, this is consistent with the idea that migration carries a psychic cost. Migrants are often isolated, alienated and suffer some form of discrimination, which leads to worse (pdf) mental health.

This, of course, is a longstanding theme of folk music. Such bluegrass standards as Blue Ridge Mountain Blues, Old Home Place and Are You From Dixie all describe a yearning to return home. Bob Dylan picked up this old story:

I pity the poor immigrant,
Who's strength is spend in vain,
Who's heaven is like ironsides,
Who's tears are like rain.

I'm not sure if this amounts to a case for immigration controls on libertarian paternalist lines - much as I'd like to see a politician say 'Immigration's good for us, but we're restricting it because we're worried about the well-being of migrants.' Instead, I'd draw two inferences.

One is that what we're seeing here might be an example of how (some) people - probably only some - mis-predict (pdf) their own tastes. They move in the hope of getting a better income whilst under-estimating the drawbacks of this in terms of greater alienation. This is one reason why we should not regard, say, the migration from country to city in developing countries as necessarily in itself welfare-enhancing.

The other is that the worse mental health of migrants might be in part due to the host country's suspicious attitude towards them. Which increases the argument for greater tolerance.