Social media has transformed young people's lives through instant connection but raised concerns about cyberbullying, harmful algorithms and impacts on health, including reduced sleep and fewer offline activities, the Murdoch Children's Research Institute study published on Friday found.
It comes as a world-first ban for under-16s reaches its six-month mark, with its effectiveness in reducing harm still unclear.
The research found adolescents who used social media for at least two hours a day were at higher risk of experiencing depressive symptoms and poor wellbeing, compared to those who used the platforms less than one hour a day.
Young people aged 12-18 found using heavier amounts of social media was associated with small but increased mental health problems one year later.
The strongest impact on mental health was seen in girls 12–13 years old.
About 1200 children in Melbourne were surveyed aged nine to 19 during the study over the 10-year period.
"This is the period when young people first start using social media and start learning how to navigate online interactions," MCRI and Deakin University's Nandi Vijayakumar told reporters.
"But it's also the period of rapid brain development and important social changes. Young people become increasingly sensitive to peer approval and social feedback and exclusion, while parts of the brain that are responsible for emotion regulation are still maturing."
Dr Vijayakumar believes early adolescents struggle to manage the challenging aspects of social media such as social comparisons, bullying, online conflict, and exposure to harmful content.
While prolonged use of social media use among teenagers is linked to declining mental health, there is limited evidence regarding whether Australia's world-first under-16 social media ban is working.
There is little indication of a reduction in cyberbullying or image-based abuse since Australian children and teenagers were restricted from most platforms in December, although some experts argue it is still too early to assess its impact.
While the study did not specifically address the ban, it suggests early adolescence should be a key focus for support and policy action, alongside developmentally sensitive measures such as parental guidance.
Greater insight is urgently needed to understand the potential impacts of social media on young people's mental health, particularly during the early teenage years, Dr Vijayakumar added.
''Early adolescence stands out as a time when higher levels of social media use are linked to a greater risk of mental health problems one year on,'' she said.
''While the increases in risk were modest in our study, even small effects can have important public health implications when large numbers of young people are exposed.
"This is why early adolescence may be the key time to intervene.''
Lifeline 13 11 14
Kids Helpline 1800 55 1800 (for people aged 5 to 25)
11°C