The researchers examined the coagulation in patients with anxiety disorders and compared them to those without such disorders and found intense fear and panic attacks increase blood clotting and may increase the risk of thrombosis or heart attack.

Franziska Geiser of the Clinic and Policlinic for Psychosomatic Medicine and Psychotherapy and Ursula Harbrecht of the Institute of Experimental Haematology and Transfusion Medicine matched 31 patients with anxiety disorders to corresponding healthy patients based on age and gender. The blood analysis, which measured various coagulation factors, produced a clear result, the researchers said.

The group of anxiety patients showed a much more highly activated coagulation system than the healthy control group.

"The increased coagulation tendency could be the 'missing link' that explains why anxiety patients have a statistically higher risk of dying from heart disease by a factor of 3 or 4," Geiser said in a statement. "Of course, this doesn't mean that every patient with a marked anxiety disorder must now worry about having a heart attack. A real health threat only arises when other risk factors, like smoking and obesity, also come into the equation."