Depression costs Canadian society $51 billion per year, with one-third of that due to lost productivity, according to the Toronto based Centre for Addiction and Mental Health.
However a recent study has drawn a link between victimization and bullying in teenage years to later adult depression.
One well-known fact about depression is the prevalence increases rapidly from childhood to early adulthood. In studies of animals, researchers have observed the long-lasting effects of negative social interactions during early adolescence; in fact, the effects of an unhappy past endure into adulthood. For these reason, researchers believe a contributing factor could be peer bullying.
Overall, 2,668 of the participants had data on bullying and depression as well as other factors that may have caused depression - such as previous bullying in childhood, mental and behavioural problems, family set-up and stressful life events.
When the other factors were taken into account, frequently bullied teenagers still had around a two-fold increase in odds of depression compared with those who weren't bullied.
The association was the same for both males and females.
There is research to indicate that girls suffer higher rates of anxiety and depression than boys.
The review, which has been published in the in the Australian and New Zealand Journal of Psychiatry, looked at 19 extensive studies conducted across 12 countries and found that teenage girls in Northern Europe, the UK and China are specifically experiencing an increase in mental health problems.
The studies leader, Dr William Bor from the University of Queensland, told the Daily Mail Australia that a combination of cultural, schooling and economic factors are most likely to be leading to the growing problem.
'There appears to be increasing school distress amongst girls as they negotiate their way through the last parts of their school careers,' Dr Bor said to the Mail.
'They face difficult choices and pressures and the modern education system appears to be more problematic for girls – so the issue there is the stress of making future decisions and how they cope with them.'
However culture is also believed to have a significant impact on mental health issues within young women, who are well known to struggle with identity and appearance issues.
'Culture has high expectation on girls in terms of appearance and weight,' Dr Bor said.
'There's a lot of speculation about the pressure on girls in terms of early sexualization and concerns they have about body image.
The most common type of bullying was name-calling (36 per cent), while 23 per cent had belongings taken from them.
Most teenagers never told a teacher or a parent, but up to 75 per cent told an adult about physical bullying such as being hit or beaten up.
The researchers said that, if this were a causal relationship, up to 30 per cent of depression in early adulthood could be attributable to bullying in teenage years.
Professor Bowes said that bullying could make a 'substantial contribution' to the overall burden of depression.
She said: 'While this is an observational study and no definitive conclusions can be drawn about cause and effect, interventions to reduce bullying in schools could reduce depression in later life.'
Dr Maria Ttofi, of Cambridge University, who wrote an editorial on the study, said the findings show the need for clear anti bullying messages to be endorsed by parents, schools and practitioners.
She also called for more research to establish the causal links between bullying and depression, and to drive specific interventions to reduce victimisation.
