A South Sudanese migrant has shared emotional testimony of how losing friends in a terror attack triggered traumatic memories of fleeing war as a child.

Key points: Victoria's royal commission into mental health has been focusing on issues facing migrant communities

Victoria's royal commission into mental health has been focusing on issues facing migrant communities The inquiry heard from a man who fled war-torn Sudan as a child and later witnessed the aftermath of a deadly terror attack

The inquiry heard from a man who fled war-torn Sudan as a child and later witnessed the aftermath of a deadly terror attack The commission was told mental illness was taboo in some migrant communities, meaning many people went untreated

It is the most grippingly personal account Victoria's royal commission into mental health has heard about the impact of trauma.

George Yengi is a refugee who made good in Australia and won a scholarship to France.

But he was then subjected to the horror of having friends murdered in a terrorist attack.

Mr Yengi came to Australia in 1999 as a 14-year-old, having escaped a Ugandan refugee camp where cousins had taken him after fleeing Sudan's civil war.

"The way that I dealt with the trauma of my childhood was to pack all those experiences down tightly in a bag and not discuss them with anyone," he told the commission.

In 2016, an idea to write and share migrant stories won him a trip to Nice, France.

Fellow students had gone to get their group pizzas on Bastille Day.

It was a fatal decision which saw them among the 87 victims of a terrorist who drove a truck through summer crowds on Nice's seaside boulevard.

When Mr Yengi went to join them he was confronted with the aftermath, including 430 injured people.

"I lost friends, and saw a lot of people … I'm sorry," he said, his voice cracking.

"I started asking questions about my own childhood," he said, after a pause.

"It is at that moment when you know that, wow, all of that stuff that happens is not OK."

Mental health 'taboo' among African migrant communities

Mr Yengi, now 34, was giving evidence at Victoria's royal commission into the state's mental health system, in hearings focusing on issues in migrant communities.

"It's never explained to us when we're growing up, never explained that you may feel this because this is what's happening," he said.

"It's a taboo. We don't talk about it."

That perpetuated a cycle he said, where peoples' health worsened, because they feared being shunned if they sought help.

"Because we don't know how to deal with it, so we hide it or push it away."

Sense of isolation

Mr Yengi described being part of a community consistently linked with crime by sections of the media as "constantly taxing".

"We've got a generation of young Africans who were born in Australia, who came here at the age of three, and all they know is this new context," he said.

"They're constantly trying to prove to themselves that they're Australians but they're not good enough."

Kylie Scoullar, an advocate for refugees and people who have experienced trauma, told the commission that among recent arrivals to Australia, 31 per cent of men and 46 per cent of women had high levels of stress, compared to 7 per cent of the general population.

"And immigrants have much lower use of mental health services than the general population," she said.

Solace in sport

Mr Yengi is now an outreach worker who focuses on engaging African youths through soccer.

It is something he hopes will eventually soften African communities' perception of mental illness.

"Real connection is what everybody really needs," he said.

"If you have a real connection, that will really help."

"Getting out there and meeting people usually helps build those connections."