Intriguingly, marital happiness long outlasted the honeymoon period. Though some social scientists have argued that happiness levels are innate, so people return to their natural level of well-being after joyful or upsetting events, the researchers found that the benefits of marriage persist.
One reason for that might be the role of friendship within marriage. Those who consider their spouse or partner to be their best friend get about twice as much life satisfaction from marriage as others, the study found.
The effect of friendship seems to be the result of living with a romantic partner, rather than the legal status of being married, because it was as strong for people who lived together but weren’t married. Women benefit more from being married to their best friend than men do, though women are less likely to regard their spouse as their best friend. [link]