If we are to believe the results of a new study from Marc Berman, a psychologist at the University of Michigan, the answer is "yes". These finding come at an interesting crossroads-- for the first time ever, more humans live in cities than in rural settings. The findings argue that the brain becomes confused and tired as it is forced to respond to the massive amounts of stimulii that are present in cities. The brain is constantly searching its surroundings, trying to anticipate threats. Not only does one have to negotiate traffic and constantly re-assess the changing visual landscape, but this is often done while carrying on a conversation or mentally planning a route through the city. Quoting from Boston.com:

The reason such seemingly trivial mental tasks leave us depleted is that they exploit one of the crucial weak spots of the brain. A city is so overstuffed with stimuli that we need to constantly redirect our attention so that we aren't distracted by irrelevant things, like a flashing neon sign or the cellphone conversation of a nearby passenger on the bus. This sort of controlled perception -- we are telling the mind what to pay attention to -- takes energy and effort. The mind is like a powerful supercomputer, but the act of paying attention consumes much of its processing power.

Interestingly, the researchers found that just showing people a picture of an urban environment was enough to cause substantial impairment to the test subject's levels of attention and working memory. Similarly, a different study quoted in the article shows that even very small amounts of exposure to nature were enough to confer significant improvement on subjects' cognitive abilities and sense of well-being. Additionally, the research indicates that living in cities may also have a harmful effect on one's level of self-control.