EU citizens in the UK brace for Friday's Brexit

Anxious, angry, abandoned. Brexit elicits strong emotions, and as Britain's departure from the European Union approaches, more than 3 million U.K. residents who are citizens of EU countries are feeling the impending separation more strongly than most.

Brexit is a huge economic and social experiment, and the United Kingdom's European residents are among the guinea pigs.

The U.K. government says they can stay and carry on with their lives as long as they apply for confirmation of their "settled status." For some, that process is easy, or mildly annoying. For others, it's deeply alienating.

Tanja Bueltmann, a Northumbria University history professor who has studied the experiences of EU citizens in Britain as they grapple with Brexit, said many felt the country's decision to leave the EU as a "real rupture."

"People were promised that nothing would change for them. Yet for a good number, even the process already changes everything," she said.

Free movement for people among the EU's member states is a core EU principle and Britain's 2016 vote to leave the bloc was, in part, a reaction to high levels of immigration from other EU nations. More than 1 million EU citizens moved to the U.K. after eight formerly communist eastern European countries joined the bloc in 2004.

Britain's departure from the EU on Friday night will end the rights of citizens from the 27 remaining EU nations to settle in Britain, and of Britons to automatically live elsewhere in the bloc. To prevent people having to uproot their lives and their families, the U.K. government says EU citizens already in the country will be given "settled status," protecting their right to live, work, study, and receive benefits.

Other EU countries have made similar arrangements for the estimated 1 million U.K. nationals who reside there.

British Prime Minister Boris Johnson has said that EU citizens are welcome and valued, but many say they resent being forced to prove their right to remain in a country they call home.

"I feel strange, really unsettled," said Elly Wright, a Dutch citizen who moved to the U.K. with her late husband in 1969. "It has moved me to the core. What has been happening with Brexit and the fact that someone like me, who has lived here for over 50 years, that my status here has to be secured when it always was secure – it makes you feel confused and angry, and also infinitely sad at times."

"My circle of friends, the people I share sadness and happiness with – they're all here," she added. "My son lives here. My husband is buried here. I'm as much part of the fabric of this society [as] anyone else."

Ms. Wright is not alone. Ms. Bueltmann's study of more than 3,000 EU citizens found some had experienced "mental health issues that range from depression to suicidal thoughts." When respondents were asked how they felt, the most frequent words were "angry," "anxious," and "unwanted."

The British government insists it has made the process of securing the right to remain as painless as possible. It's free – a proposed 65 pound ($85) fee was dropped after an outcry – and can be completed on a cellphone. The government says by the end of 2019, more than 2.7 million people had applied and almost 2.5 million had been granted either settled status or "pre-settled status," for those who have lived in the EU for less than five years. Only six applications were refused.

Rights activists say the statistics don't give the full picture. They don't account for those who have struggled with the process – such as elderly people who may lack documentation – or those who don't know they need to apply.

Others worry about trouble down the line. The U.K. government has given EU citizens until the end of June 2021 to apply for settled status. It's unclear what will happen to those who don't.

Tahmid Chowdhury of immigration advice charity, Here for Good, said the deadline could mean "hundreds of thousands of people become undocumented overnight and don't have any legal right to remain in the U.K."

Jonny Oates, a Liberal Democrat member of Parliament's House of Lords who has tried to secure stronger guarantees on EU citizens' rights, said that "as the law stands at the moment, all those people would be automatically criminalized and subject to deportation on the 30th of June 2021."

The government insists people needn't worry – there won't be deportations after the deadline expires. But it has also sent mixed signals. The prime minister said last month that EU citizens had been "able to treat the U.K. as though it's basically part of their own country," a remark whose tone sent chills through many Europeans who call Britain home.

Many EU citizens say they would feel better if they had physical proof – a piece of paper or a passport stamp – to confirm their status. The government's settled status program is a digital-only affair.

Both the European Parliament and London Mayor Sadiq Khan have expressed fears that European citizens risk future discrimination from landlords and employers because they won't have an easy way to confirm their residence rights.

They point to the Windrush scandal, which erupted in 2018 when it emerged that people who came to Britain decades ago from the Caribbean had recently been refused housing, jobs, and medical care or threatened with deportation because they didn't have the paperwork to prove their status.

Ms. Wright, the Dutch-born long-time U.K. resident, said she worried the EU citizens' status was "a Windrush waiting to happen."

"It makes you feel so powerless that we have had no say in this, what is happening to us now," she said. "And to me, it makes me feel neither here nor there."

This story was reported by The Associated Press.