The aftermath of terrorist 9/11 attacks on America is still being felt. A Weill Cornell Medical College public health study says that the terrorist incident caused about one million former smokers to resume their habit due to the high stress levels they experienced after the devastating incident.

The study looks at the after affects of such attacks on the society including the 1995 Oklahoma City bombing.

"This helps us better understand what the real costs of such disasters are in human and economic tolls, and it suggests ways that such future stressful reactions that result in excess smoking might be avoided," said the study's author, Dr. Michael F. Pesko, an instructor in Weill Cornell Medical College's Department of Public Health.

Dr. Pesko said that the 9/11 attacks led to a considerable 2.3 percent increase in smoking rates nationwide that started soon after the disaster stuck the country and continued till the end of 2003, same time when the analysis of the data also ended. In comparison, the Oklahoma City bombing didn't report any effect on people's smoking habits.

Apart from smoking levels, the study traced self-reported stress in families with active-duty and reserve members of the military and among higher-educated groups.

"This study provides the first unbiased estimate of the effect of stress on smoking, and the finding that there was such a big increase in smoking nationwide, seemingly due to one event, is extraordinary, and surprising," says Dr. Pesko. "It sheds light on a hidden cost of terrorism."

"There is a consensus in the research community that stress is a very large motivator for individuals to use substances, but this has not really been studied very thoroughly."

In order to examine the relationship between stress and substance use Pesko referred two domestic attacks and analyzed the data from the Behavioral Risk Factor Surveillance System and Centers for Disease Control and Prevention. After comparing around 1,657,985 responses from the fourth quarter of 2001 through 2003,  it was found that between 950,000 and 1.3 million adult former smokers across the country took up the habit once again.

"I was really surprised to find that former smokers across the nation resumed their old habit," Pesko said. "I was expecting to see impacts just in the New York City area - or, at most, the tri-state area."

Pesko claimed that the behavioral change cost the government around $530 million to $830 million till 2003.

Pesko said that this study now alerts the health professionals on future stress-inducing events.

"......free nicotine replacement therapy and more substance abuse screening during regular medical appointments following terrorist attacks, or any such event that is likely to stress the nation," Pesko said.

A previous study found that the rate of miscarriages among women carrying male babies also went up significantly after the 9/11 attack. The study revealed that males seem to be more susceptible to stress even in the womb.