But University of Otago researchers have discovered three key things that can help them go from "getting by" to "thriving".
Senior author and professor of psychology Tamlin Conner said sleep was the biggest contributor to young adults’ wellbeing, followed by a healthy diet and being physically active.
"This age group faces unique pressures ... that can lower happiness.
"Understanding what lifestyle factors support wellbeing can help young adults not just ‘get by’, but thrive during this critical life stage," Prof Conner said.
Research leader Dr Jack Cooper said taking steps to feeling better did not have to be complicated.
"Young adults don’t have to reach some objective benchmark of healthiness to see wellbeing improvements.
"Sleeping a little better, eating a little healthier, or exercising even for 10 minutes longer than you normally do, was associated with improvements to how you feel that day."
The research surveyed more than 1000 people and studied the data from two daily diaries of another 1000 people aged 17-25, all from New Zealand, the United States and the United Kingdom.
Prof Conner said young people who got good-quality sleep, ate more fruit and vegetables and stayed physically active were better off.
"Of these healthy habits, sleep quality stood out as the strongest and most consistent predictor of next-day wellbeing, but eating fruit and vegetables and being active also helped boost wellbeing."
She said the interplay between sleep quality and diet was an interesting discovery.
"Across the two daily diary studies, young adults who ate more fruit and vegetables after a poor night’s sleep experienced less of a drop in wellbeing the next day.
"While poor sleep still predicted reduced wellbeing, healthy eating appeared to buffer some of its negative effects."
She said this suggested that improving basic behaviours, especially sleep, could give meaningful benefits.
"Importantly, these changes are practical and can be made without costly interventions."
