The precise cause of Traveler's Thrombosis, while currently not clear, appears to be related, in part, to long periods of sitting and inactivity. The decrease in activity may lead to inadequate circulation of the blood in the legs. In addition, the veins may be slightly constricted, which could also impair circulation in the legs.
Other conditions that alter blood flow or normal clotting mechanisms may make some people more likely to develop a DVT. Some of these risk factors include a prior DVT, certain heart diseases, cancer, pregnancy, smoking, older age, and some blood clotting disorders. Recent major surgery or trauma is also a risk factor.
Certain medications may also contribute to formation of the thrombus. Birth control pills and related hormones have been found to make some people slightly more susceptible to forming DVTs.