TORONTO -- Older refugees have high levels of depression even decades after immigrating to Canada, mostly due to past traumas and lack of social support, according to a new University of Toronto study.

The findings -- released this week in the Journal of Immigrant and Minority Health —determined that among a study sample of 29,670 Canadians aged 45 to 85 taken from the ongoing Canadian Longitudinal Study on Aging, refugees were 70 per cent more likely to suffer from depression than natural-born citizens.

“Our findings indicate that the refugee experience casts a long shadow across an individual’s lifespan,” first study author and University of Toronto doctoral student Shen Lamson Lin said in a release.

Lin said the researchers’ data did not capture the exact reasons for the high levels of depression among refugees, but they believe it “may be influenced by exposure to pre-migration traumas such as genocide, forced displacement, human trafficking, sexual assault, famine and separation from family.”

The study investigated several factors that may have influenced levels of depression, including age, sex, marital status, income, education health and social contracts. But “even when these characteristics were accounted for, refugees still had higher odds of depression that individuals born in Canada,” the release said.

The researchers also investigated depression among immigrants who did not arrive as refugees, in order to better understand post-migration challenges, such as racial discrimination, language barriers and higher levels of unemployment, that affect all immigrants to Canada and the pre-migration trauma unique to refugees.

The prevalence of depression among non-refugee immigrants was measured at 16.6 per cent, similar to that of their Canadian-born peers at 15.2 per cent. The prevalence of depression among refugees was measured 22 per cent.

The results “suggest that post-migration challenges are less important than pre-migration traumas when it comes to depression,” said study author and University of Toronto professor Esme Fuller-Thomson.

"The greater prevalence of depression among refugees, half of whom arrived more than four decades ago, underlines the importance of providing mental health resources for our refugee community both immediately after arrival, but also in the ensuing decades,” Fuller-Thomson said.

The researchers concluded that social support is key for refugees and that a lack of social support was associated with higher levels of depression among them – with refugees significantly more likely to report that they lacked someone who showed them love and affection, someone to confide in and someone to give them good advice in a crisis than those born in Canada.

The study authors indicated that the findings could also have important policy implications for the two types of refugee sponsorship programs in Canada: government assisted and privately sponsored.

Privately-sponsored refugees are supported by a network of volunteers who provide extensive assistance with settlement issues including housing, health and employment. A recent study on Syrian refugees found that privately-sponsored individuals had more help in daily errands, fewer unmet needs and a higher employment rate than their government-assisted counterparts.

“This highlights the importance of investigating ways to promote powerful positive social relations among refugees and asylum seekers in their families, neighbourhoods and communities,” said study co-author and University of Victoria sociology professor Karen Kobayashi.