An interesting research finding was published in the Journal of Economic Behavior and Organization. In an analysis covering for many geographical units including countries and states, it was found that the more happy (satisfied) is the region, the higher the suicide rate. I mean, there is an association between these two metrics. The main explanation for the positive association between happiness and suicide rate was that folks tend to compare themselves with others and if there are too many happy people, the unhappy ones will likely be even more unhappy.
Notice that the correlation was found at the geographical level and the researchers try to establish a causal link. This is the well know ecological fallacy, about which you can read more here and if you want to dive deeper in the subject there is this very good book.
The idea is that regions with higher satisfaction levels (or higher % of people satisfied) will usually have also higher rate of suicidal. But that is just an association, it is not a causal link, that is, it is totally possible that these things are associated but they don't cause one another. Moreover, when the association happens at the aggregated level like this one, it seems to me that the number of confounding factor can be enormous and difficult to pinpoint. That is not to say that this kind of analysis is useless, though, but I do think they did not go far enough on testing these confounding factors. The article mentions demographic variables as control, but I think region level variables should be accounted for as well (GDP, temperature, health and development indicators...). It could be, for example (and this is really just a fake example, although I do think the development level of a region might have something to do with this association), that development causes more extreme situations, among them it causes both happiness and depression. That could be why things are associated, they are both cause by the degree of development of the place, meaning that the association is spurious, there is not causal link, it is a third variable (development) which in fact causes both.
I heard in the radio a while ago that allergies are much more common in developed countries, so maybe we could also find an association of allergy with satisfaction and suicide rate. I mean, when looking at data at the aggregated (regional) level, we need to be careful on concluding things that in fact happen at the individual level. Unfortunately we can find explanations (that are just hypotheses) for pretty much any correlation, but explanations that we find after looking at the associations are very weak in statistical validity.
