Culture influences incidence of depression
Curtin University's Dr Derwin Chan led a team investigating the link between emotion and depression across China, Ghana, India, Mexico, South America and Russia.
Dr Chan's research confirmed a known relationship between experiencing depressive symptoms and encountering negative emotions, such as worry, rush, irritation and stress.
However the new research observed important cross-cultural differences in this relationship, including a difference in the reported incidence of depression.
The study found Russians and Indians displayed the strongest link between negative emotion and depressive symptoms, and reported relatively high levels of clinically diagnosed depression (3.76 and 3.35 per cent respectively).
In contrast, populations in China and Ghana demonstrated a weak link between negative emotion and depressive symptoms, and had the lowest levels of clinically diagnosed depression (0.3 and 1.24 per cent respectively).
"Negative emotion fails to predict depression in China and Ghana," Dr Chan says.
"This phenomenon supports the argument that the link between negative emotion and depression can't be generalised to all countries."
Dr Chan's team also confirmed the link between negative emotional variability and depression—a relationship strongest in India.
"Not only do we have to stay away from negative emotion, but also the swing of negative emotions up and down," Dr Chan says.
"The more fluctuations we experience, the more likely [we are to] display depressive symptoms."
The study used population-based data sets from more than 47,000 adults, collected as part of World Health Organisation research into adult health and ageing between 2007 and 2010.
The team used hierarchical regression analyses to statistically control the effect of variables such as age, income and alcohol use, but did not correct for the effect of social desirability or memory bias.
Dr Chan says his research only demonstrates a correlation between emotion and depression.
"It's not causal; negative emotions are not causing depression," he says.
Depression affects an estimated 350 million people worldwide, with symptoms including sadness, low self esteem and a sense of meaninglessness.
This is the first investigation into the association between emotion and depression outside developed countries, like North America and Western Europe, from which the bulk of previous research has emerged.
"These findings clearly show the predictive power of emotion and fluctuation in emotions on depression varied across the countries," Dr Chan says.