Genetics and stress hormones are among the factors known to affect our mental health, but researchers are investigating another possible influence -- the environment.

We've long assumed that when it comes to our surroundings, green is good, and too much gray is bad for us. Researchers now are testing that notion by collecting real data.

Temple University's Mark Salzer recently researched where Philadelphians with mental illnesses live.

"We were able to find that people with serious mental illnesses live in areas where there are more crimes, there is more substance use, property in those communities are more broken down," he said.

Salzer also suspects that living in these neighborhoods may add more challenges to living life with a mental illness.

"There are more social problems in those communities than in neighborhoods that a typical Philadelphian might live in and our interest is in trying to understand what living in that neighborhood ... how that might impact somebody's life and behavior," Salzer said. He said he suspects that the mental health effects of living in these neighborhoods are often falsely attributed to a person's illness.

In the United Kingdom, researchers are examining greener pastures. Ian Alcock of the University of Exeter studies the mental health benefits of living in green urban areas.

"What we found was that people who moved from a typical English urban area with a low level of green space to a typical English area with a very high level of green space had an improvement in mental health that was broadly equivalent to about one-tenth of the benefit from having a job rather than not having a job, and about one-third of the benefit of being married to not being married," he reported.

While the effects he found are modest, Alcock said they are meaningful.

"When there's investment in urban green space, that small benefit is multiplied by the large number of people who can take advantage of it," he explained.

These benefits are not only significant, but long term. Alcock and his team continued to observe positive benefits in well-being for several years after the move.