"This does tend to be a well-documented finding, but it shouldn't be the case for everybody," she told the Weekend Herald.
Ms Girme said the number of singletons was rapidly increasing, which could be put down to more younger people putting off relationships for the sake of career-building and travel, along with rising rates of divorce and solo parenting.
"We're finding that people across all life stages are single, and it does seem strange and unusual to think that every one of those single people are going to be miserable."
Drawing upon data from more than 4000 adult participants of the NZ Values and Attitudes Study, she compared wellbeing between those in and off the market and gathered information about how people try to maintain their close relationships.
People with "high avoidance goals" - those who purposely kept away from conflict and hurtful arguments - made for happy singletons, probably because they find relationships hard to manage.
Although the same category of people in relationships were also happy, previous research suggested constantly trying to avoid fights with quick fixes could be detrimental to the relationship over time.
Ms Girme said her results also found the ever-optimistic people "high in approach goals" who actively try to improve their relationship are the most happy when in a relationship compared with singletons.
"So, you might have Sam, whose 'avoidance goals' means he buys his girlfriend roses so she doesn't get mad about him working late."
And then you have Sally "who generally tries to avoid conflict, and maybe the thought of being in a relationship is quite anxiety-provoking. So being single frees her of that worry.
"Lastly, you have Jack, who is motivated by 'approach goals' which means that he surprises his girlfriend with a romantic dinner because he's trying to grow intimacy."
Benefits of a single life included having more time to build better relationships with friends and family, and pursuing personal interests.
"Being single isn't necessarily this negative experience that everyone thinks it is."