Research in the Journal of Happiness Studies shows that not only are married couples happier in the long-term than single people, but being best friends with your spouse is linked to even higher levels of satisfaction.
Shawn Grover and John Helliwell of the Vancouver School of Economics in Canada looked at data from the British Household Panel Survey including responses from over 30,000 people between 1991 and 2009 and from the United Kingdom's Annual Population 2011 to 2013 Survey of over 300,000 people.
the researchers found that married couples and even non-married couples who were living together were more satisfied with their lives than single people and that when couples were best friends, the benefits were even stronger.