Just a few minutes ago I found this article:
http://www.spiegel.de/wissenschaft/medizin/0,1518,705542,00.html
Since few people here will be able to understand german, here comes a short conclusion:
A study shows that obesity is a cause of physical inactivity and not vice versa.
British scientists say that most studies about obesity are cross-sectional study that only test at one point of time but not over a period, thus they cannot distinguish between cause and consequence.
These scientists made a study in which they observed children over several years. If children of age seven had a higher body fat percentage, they were likely to decrease their physical activity afterwards.
Final note about this one: I don't doubt physical activity or sports to be important.
Actually I didn't think that much about the contents of this article but rather about a thought I had some time ago:
Often I read articles about scientific studies which observe two values, such as (any random made up example) time of playing Starcraft per week and IQ. Then, the scientists (or sometimes only the writing journalist) immidiatly draw a conclusion. Such as playing Starcraft makes people smart for the example above.
But often they have no evidence whatsoever that this relationship is true. Maybe it's just that low-IQ-people don't like Starcraft so the average IQ of starcraft players is higher than average of their age brackets.
One of the most stupid conclusions I ever heard of was made up by Christian Pfeiffer (criminologist and director of the criminolical research institute of Lower Saxony, also former justice minister of Lower Saxony):
Playing violent video games makes people more agressive and is a keystone of kids becoming spree killers. Some of you might have heard of the three or four spree killings at german schools over the last ten years. Since two or three of them played violent games, many politicians and low quality media (BILD for example) started stating that shooter games would make young peoples loosing sense of reality, make them angry and violent and help them to improve their aim for real guns.
To get the arch to the original topic:
Isn't it just absolutely logical that guys who are agressive, violent and dream of shooting others play games that display violence? Quite obviously they like to see themselves as persons that others fear and who are superior to other people. This is certainly a thing that can be seen in video games if the player wishes to. Unsurprisingly, the police stated that Robert Steinhäuser (I think he was the first spree killer that became famous in this debate, possibly just because there weren't any killing sprees of a long long time before) did play Counter-Strike, but not for a long time. I guess he just didn't have the patience to develope skills to realize the image he wanted to have ingame. Rather, he played games like Doom (single player) which certainly any idiot could win and feel like a god compared to the AI monsters.
This would mean that "Playing violent video games" does not lead to "Higher risk of becoming a violent spree killer", but rather that both of these traits are a consequence of the same cause, what would make "playing violent video games" a symptom (in some rare cases only of course), but not a cause and would make forbiddance absolutely pointless.
I wish I had some more examples since I have this feeling that some guys didn't think about cause and consequence carefully every few days, sadly my memory is bad in such things. So I'll just take the first article that fits to this kind of thinking (even though it's very remotely):
"Small people get a heart condition more likely"
The only data that has been collected is the size of persons and their history of cardiac problems/illnesses. So it is possible that having a weak and prone heart leads to a small body size or that both of these traits are related to some other cause, but are not cause and consequence to each other.
You might slightly notice that I had some arguments with teachers at school about this (also, sometimes a problem to finish certain tests in time °_°) although I try to keep such arguments short
(actually it led to very good results in biology, given that I had the time -some tests scored rather badly compared to my skills because I wasted too much time on it-, and bad ones in religious education)
I hope someone cares or feel the same out there, I really feel that many people don't think twice about cause and consequence and gain many hasty and wrong ideas from that.