The reason living in a messy environment can cause emotional distress has a lot to do with our visual field and what we can mentally and physically keep up with. A nice, neat living space feels good, partly because there's less to look at -- there's less for the brain to do in an uncluttered space. This helps us focus on the task at hand: One 2011 study published in the Journal of Neuroscience found that study participants were more productive and less irritable if their workspace was clear of visible clutter. This is because an overwhelmed brain makes the stress hormone cortisol, which is great for helping you run away from a swarm of angry bees, but it's not helpful when you're hanging out all day at work, steeping in low levels of cortisol. Living on a constant cortisol drip can lead to anxiety, depression and other mental health problems like post-traumatic stress disorder.
Research shows that women's cortisol levels are affected by a messy living situation more than men's. Two studies published in 2010 in the Journal of Personality and Social Psychology and conducted by a team of researchers at the University of Southern California found that, among 30 two-income couples with school-aged children living in the Los Angeles area, the woman in the relationship was more likely to take the psychological hit from a messy house. In the first study, wives were the ones who experienced elevated cortisol levels throughout the day as a result of a cluttered living space, and because they were more likely to be responsible for household chores, their stress hormones remained high after they got home.