CANBERRA - The mental health and wellbeing of Australian children have continued to decline in the wake of the COVID-19 pandemic, research has revealed.

The study, which was published by University of South Australia (UniSA) researchers on Wednesday, examined measures of wellbeing among more than 56,000 South Australian children aged 9-14.

It found that the mental health of children has gradually declined over the past six years, particularly in the time during and post-pandemic.

Female students, those at the top end of the age group and those from lower socioeconomic backgrounds were most likely to have poor wellbeing.

"During the pandemic, children had to change the way they learn, play and socialize, all the while living in an environment of widespread uncertainty and anxiety," Dot Dumuid, lead author of the study from the Alliance for Research in Exercise, Nutrition and Activity at UniSA, said in a media release.

"Children and young people have dealt with school closures, isolation, social distancing and cancelled extracurricular activities, and this has led to decreased levels of physical activity and increased sedentary time."

"Now that pandemic restrictions have been lifted, life has not necessarily gone back to how it was pre-pandemic. And when we assessed how children have fared in terms of wellbeing across this period, the news was not good," Dumuid said.

Life satisfaction, optimism, happiness, perseverance, worry, sadness, emotional regulation and cognitive engagement were considered as measures of wellbeing.

Exercise and healthy eating were generally associated with higher wellbeing.

Researchers used the findings to call for urgent and equitable support for the wellbeing of all young Australians.

"Everyone has a responsibility to look out for the next generation. We all play a role in the overall wellbeing of our kids," Dumuid said.