Because the evolutionary mechanism sets off a false alarm in some people, they are much more sensitive to levels of carbon dioxide in the bloodstream. Their bodies overreact. The prevailing theory is that panic attacks are often triggered by respiratory problems that are not recognized as such, says Cohen. People who have them don't really know what's caused them. There's trouble breathing, a racing heart, you often break out in a sweat.
Panic attacks are very, very scary.
However, other anxiety disorders like social phobia or a fear of insects might cause the same respiratory distress symptoms, but they generally start exclusively with anxieties over specific stimuli. It's not that everybody who gets panic attacks smokes, says Cohen. And not everybody who smokes gets anxiety disorders. Genetics likely creates vulnerability, determining who among smokers will develop an anxiety disorder. But social environment also plays a role.