According to the research, which was commissioned by J Walter Thompson, a national crisis such as a war, could see consumer buying habits change drastically.
JWT North American president Bob Jeffrey said: "The Anxiety Index study offers irrefutable evidence that marketers today face an increasingly fearful audience whose purchasing behaviours are influenced, not by consumer attitudes toward war or political affiliations, but by their levels of anxiety during a time of crisis."
Unsurprisingly, the worst sector to be hit is travel, with 43% saying they would not book international travel during a war.
The second sector to be hit was the new car market, down 28%, followed by jewellery, down 27%, and appliances, which would fall 23%.
Advertisers can help ease the anxiety of US consumers, the study said, with supportive messages focusing on values such as security, hope and the family.
Rather than feeling advertising is inappropriate, 51% of those who took part in the study said they felt it was reassuring, and symbolised a return to normal life.
Consumers also said they looked for truth in ads, with 62% of those surveyed saying ads should be sensitive to what people are feeling, not full of opinion or hype. They said they preferred messages that include facts and information about products, and 52% said that patriotic ads made them feel happier.
Ads should relate to staying at home with the family, according to 46% of those questioned, as opposed to going out.
Print media looks set to see the most dramatic change in its audience profile in the event of a war, as more young people said they would increase their news consumption more than any other group. This would create more opportunities for advertisers to reach this audience.
The Anxiety Index study will be carried out every eight weeks for six months to gauge the impact of marketing campaigns on consumer feeling.
The first study was carried out among 500 consumers all aged over 18 on the weekend of February 18.
If you have an opinion on this or any other issue raised on Brand Republic, join the debate in the Forum here.