According to the Chicago Dental Society, 65 percent of dentists say they are hearing about an increase in jaw clenching and teeth grinding in their patients [source: Kramer]. They also say that 75 percent of their patients report greater stress in their lives. The correlation is not coincidental, as the No. 1 cause of teeth grinding is believed to be stress and anxiety.
If you're under a lot of stress and your mom or dad is a bruxer, chances are good you will grind, too, as teeth-grinding is thought to be an inherited trait. And if you're also a young smoking woman, you're pretty much guaranteed to be a teeth grinder. Three times more women than men suffer from bruxism, smokers are five times more likely to have bruxism episodes and the condition afflicts those between the ages of 20 and 40 the most [source: Hurst].
Teeth grinding can also be a side-effect of certain psychiatric medicines such as antidepressants like Lexapro.
One final potential cause of teeth grinding is an abnormal alignment of the upper and lower teeth. This causes a condition known as malocclusion and can be diagnosed by your dentist. Typically, when the bite is corrected, a bruxer suffering from malocclusion will stop grinding.