Other reasons for committing infidelity included consuming alcohol and seeking a thrill.
Infidelity in this age group was found to be most common because millennials - typically defined as people currently in their 20s or sometimes up to mid 30s - are trying to sort their adult life out, the team from the University of Tennessee said.
WE MATURE LATER ON
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MailOnline's resident sex and relationship expert Tracey Cox also believes people in their 20s take longer to mature emotionally.
"Our grandparents were marrying and having children in their 20s but it's taking longer for us to grow up now. We're maturing much later, so this research makes sense.
"Our 20s is now equivalent to what used to happen in our late teens. Millennials are testing commitment and testing the relationship they're in at a later stage.
"If you're feeling satisfied, you'll stay faithful. If you're not, you'll try a new person to see if they can satisfy what's lacking in your current relationship."
She also said young people living with their parents - due to economic challenges preventing them getting on the housing ladder earlier - could play a role.
"It could also be because millennials are forced to stay living with their parents much longer than before and missed out on the whole group of single friends flatting together period," she said.
"They didn't get the chance to truly kick up their heels if they move from home into a serious relationship in order to be able to afford living away from home.
"The most common reason for cheating with other generations is a reaction to the monotony of monogamy."
FACTORS THAT LEAD TO INFIDELITY
In the study, 104 heterosexual adults were surveyed who on average were 22 years old and admitted being unfaithful within the last six months.
Before the survey, participants were given a paragraph to read that shared how common cheating is to help them feel more open to discussing their indiscretions.
The researchers asked them how attached they were to their partners and to give details about why they chose to be intimate with someone else.
Researchers identified two different relationship attachment styles that came into play with cheating.
First, individuals who avoided getting too close to others were more likely to believe their partners weren't meeting their needs - this is known as having an avoidant attachment style.
And second, there is the anxious attachment style. These are people who feel worried about losing closeness with their partners - and as a result may be more likely to push their partners away.
