By Pat Loeb

PHILADELPHIA (CBS) — As a battleground state, Pennsylvania is being treated to a steady stream of negative political ads and, with campaigns spending unprecedented amounts of money, it’s likely to get worse as election day gets closer.

Strategists say negative ads are effective at influencing votes, but could they also be influencing our mood? It’s well-established that the low light of autumn causes depression, but could a virtual cloud cover of nasty, grating ads have the same effect?

Temple University psychiatry department chair William Dubin thinks it could. The ads, he says, inspire feelings of hopelessness, despair and anger.

“One of the hallmarks of depression is a sense of hopelessness, helplessness and pessimism,” he says. “So, that negative tone could contribute to the sense of hopelessness and pessimism.”

Dubin knows of no specific research on negative ads and mood but there is research that ties negative thoughts to depression and studies showing that listening to depressing stories makes people sad.

Drexel University political science professor Bill Rosenberg believes strategists are aware of the depressive effects of negative ads.

“The way they actually work,” he says, “is not so much to change people’s minds but really to change their connection to the political process. What it does is for many people is, it gets them to think, ‘all these guys are really bad guys and I don’t really want to have anything to do with them’ or ‘I should just stay away from the political process because it’s not something that I want to engage in.’”

Rosenberg says some campaigns want to discourage people from voting, if they are likely to vote for their opposition.

“The research shows this is more likely to happen among minority individuals. They’re more likely to be discouraged. Also, people who are less confident in their own political competence, their knowledge, their ability to effect change.”

Dr. Dubin recommends shielding yourself from negative ads, to the extent possible, or counteracting them with positive experiences and unbiased information.