According to the American Psychological Association journal Emotion, early birds, or morning sleep chronotypes, are generally healthier than night owls due to the way their cycles synchronise with the rise and fall of the sun. The inability to synchronise with natural rhythms can have an adverse effect on night owls, or evening sleep chronotypes, who are more prone to depression, alcohol and drug use, and insomnia.
According to scientists at Germany's Aachen University, there are structural differences in the brains of people with different sleep-wake tendencies. Night owls show reduced integrity of white matter in several areas of the brain, something that has been linked to depression and disruptions of normal cognitive function. Night owls may also be fatter than their "up and at'em" cousins, according to a study by the Department of Psychology at Drexel University in Philadelphia.
It's not all bad news for night owls, however, with a 2009 study by the London School of Economics and Political Science finding night owls to be generally smarter than early risers. It seems the same disruptive cycles that may make night owls less healthy can have an opposite effect on intelligence, with nocturnal activities more novel and innovative from an evolutionary perspective.
In a separate study by the University of Madrid, evening types demonstrated the kind of intelligence associated with innovative thinking, prestigious occupations, and better incomes. Night owls scored higher than morning types on inductive reasoning, and showed a greater capacity to think conceptually and analytically. Not only is this a good estimate of general intelligence, it is also a strong indicator of academic performance and is more likely to lead to high paying jobs.
If the goal is to be healthy, wealthy, and wise, it appears we are all doomed. While early birds are generally more healthy than night owls across a range of studies, it seems night owls have the tendency to be both smarter and richer. With pros and cons to each sleep pattern and unclear causal links in many cases, perhaps the best advice is also the most simple. Get around eight hours of sleep per night, try to stay consistent with your sleeping schedule, and make the most of whatever time you are awake.