Steven Levitt wrote about a study that looked at smoking and PTSD. Here is an excerpt:

The Journal of Clinical Psychiatry recently published a paper on the relationship between smoking and post-traumatic stress disorder. This newspaper report on the article starts out okay:“Post-trauma mental health disturbances such as post-traumatic stress disorder (PTSD) are associated with increased smoking, either by starting to smoke or an increase of tobacco use,” write Dr Peter G Van der Velden, of the Institute for Psychotrauma, Zaltbommel, the Netherlands, and colleagues.

That certainly makes sense. The article continues:

However, few trauma studies have examined whether smoking is a risk factor, or “marker” for PTSD or other mental health disorders following a disaster.That seems a reasonable thing to test as well. You find a bunch of smokers and non-smokers before a traumatic event. You subject them to a traumatic event. Then you see how they fare. It won’t tell you anything about the impact that smoking has on coping with trauma, but it will tell you something about whether the kind of people who smoke might fare better or worse in response to a tragedy.

To look into that aspect, the researchers conducted surveys 18 months and 4 years after a fireworks disaster in Enschede, the Netherlands. Included were 662 adult victims and 526 residents of another Dutch city who were used as a comparison group.

Oops…by surveying victims for the first time 18 months after the disaster we cannot even answer the question about whether the kind of people who smoke respond badly to tragedy because they are classifying people as smokers based on whether they smoke 18 months after the event. If you look back up to the first passage in italics in this blog post, you will see that we already know that people start to smoke after traumatic events. Presumably, the harder the tragedy hits you, the more likely you are to take up smoking. Of course, you could ask people whether they smoked before the tragedy, but it appears that these researchers didn’t bother, or at least aren’t using the information (or maybe they do but it isn’t mentioned in this media report).

Victims who smoked at the first evaluation were more than twice as likely as those who did not smoke to have severe anxiety symptoms, nearly twice as likely to have severe hostility symptoms, and close to three times as likely to have a diagnosis of disaster-related PTSD at the 4-year evaluation.

Interesting, perhaps, but I have no idea how to interpret the result. One thing I can guarantee you I would not conclude with any confidence is what the authors conclude:

If these findings are confirmed by other studies, disaster victims who smoke may be able to reduce their risk of developing mental health disturbances if they quit smoking, Van der Velden and colleagues conclude.

What?! For starters, there is nothing in the study about quitting smoking — only about people who do smoke. Second, where do they get the idea this relationship is causal, or that the direction of causality runs from smoking to anxiety rather than vice-versa? This is not too different than advising sick people to avoid hospitals because people who visit hospitals die at a much higher rate than people who don’t.