Older Australians living in areas with more tree canopy had fewer depressive symptoms over time, a new study of more than 1000 people aged 70 to 90 has found.
- Greener neighbourhoods may help reduce depressive symptoms in later life
- Long-term exposure to tree canopy was linked to lower levels of depression
- Findings reinforce the importance of designing neighbourhoods to support healthy ageing.
New ACU research, together with UNSW Sydney's Centre for Healthy Brain Ageing (CHeBA), followed 1031 older Australians for up to 12 years as part of the Sydney Memory and Ageing Study.
According to the study, published in the Journal of Affective Disorders, living in neighbourhoods with more tree canopy may help protect against depression in older age.
Researchers examined neighbourhood features near each home, including tree canopy, parkland, access to oceans, rivers and lakes, access to amenities and air pollution to see how they were associated with changes in depressive symptoms over more than a decade.
The strongest and most consistent finding was that greater long-term exposure to tree canopy was linked to lower levels of depression.
Those who lived in areas with greater tree canopy experienced fewer depressive symptoms over time.
Senior author and leading behavioural scientist with ACU's Mary MacKillop Institute for Health Research (MMIHR) Professor Ester Cerin said the findings reinforce the importance of designing neighbourhoods that support healthy ageing.
"Creating greener neighbourhoods is a practical way to help foster healthier, more connected communities," Professor Cerin said.
"While no single environmental feature can prevent depression, increasing tree canopy may contribute to neighbourhoods that encourage physical activity, social interaction and other behaviours that support mental wellbeing across the lifespan."
The findings highlight the potential role of urban planning in supporting healthy ageing and mental wellbeing.
Depression affects almost one in five adults over the age of 60 worldwide and is associated with poorer physical health, cognitive decline, reduced independence and lower quality of life.
Lead author UNSW Scientia Associate Professor Simone Reppermund said trees provide far more than shade and visual appeal.
"Neighbourhoods with more tree cover may encourage people to spend time outdoors, be physically active and connect with their communities – all of which are important for maintaining good mental health as we age," she said.
Researchers also investigated whether changes in neighbourhood environments over time influenced mental health.
While some results initially appeared unexpected – including increases in tree canopy and reductions in nitrogen dioxide (NO₂) being associated with higher depressive symptoms – further analysis revealed these findings were largely explained by participants who had relocated during the study.
Many of those who moved did so because of declining health or into residential aged care facilities, where greener surroundings are often more common.
These life circumstances, rather than the environmental changes themselves, are the more likely explanation for the increase in depressive symptoms.
"Our findings reinforce that neighbourhood environments influence mental health in complex ways," co-lead author Dr Annnabel Matison said.
"Life events such as relocation, illness and the transition into residential aged care need to be considered when interpreting these relationships."
Senior author Professor Perminder Sachdev AM, Co-Director of CHeBA, said the findings added to growing evidence that healthy cities are important for healthy ageing.
"As Australia's population ages, creating neighbourhoods that support both physical and mental wellbeing will become increasingly important," he said.
"Urban greening initiatives that increase tree canopy may offer benefits that extend beyond environmental sustainability to support brain and mental health.
Further studies in different populations and geographic settings are needed to better understand how neighbourhood environments interact with ageing, health and life transitions to influence depression, the researchers said.
