Hong Kong's protests have ratcheted up already high stress levels among young people as they despair for their future under Beijing's heel in a city where anger has long simmered over inequality and sky-high property prices, experts warn.

The international financial hub has been rocked by a month of huge peaceful protests as well as a series of separate violent youth-led confrontations sparked by a proposed law that would have allowed extraditions to mainland China.

Compared to the huge optimism-tinged pro-democracy "Umbrella Movement" rallies in 2014, the recent protests have been darker and more desperate, culminating in the storming of parliament last Monday by hundreds of young, masked demonstrators.

The movement has also taken on a distinctly funereal tone, publicly mourning at least four people who have taken their own lives in recent weeks after leaving political messages.

Experts stress that most suicides have complex, multiple triggers and have warned that depicting the four as "martyrs" to the protestors' cause risks encouraging copycat acts.

An army of social workers, counsellors and other volunteers have mobilised across the city to address a spike in demand for mental health services.

"These students are gambling their youth to defend this place, it's very fragile," said Roy Kwong, a pro-democracy lawmaker with a social work background who has been praised for trying to keep demonstrators from harm.

Winnie Ng, a counsellor and drama therapy practitioner who has volunteered in recent weeks, said many young Hong Kongers were under huge stresses before the latest protests.

She pointed to huge inequality in the cramped city, the world's most unaffordable property market, a pro-Beijing local government that has faced down demands for greater freedoms and the failure of the 2014 protests.

"I personally think when everything in life is related to politics, it pushes life in Hong Kong into a very dejected state," Ng told AFP. "Many people really can't see hope".

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Data points to an uptick in calls for help. The Samaritans told South China Morning Post that calls to its line were up five times in the last month.

Support platform Open Up said some days had seen spikes of 200 and 450 text messages seeking help during the protests compared to its usual average of 60-80, local newspaper Ming Pao reported.

- 'Last straw' -

Paul Yip, director of the Centre for Suicide Research and Prevention at the University of Hong Kong, said the extradition bill was "just the last straw to kill the camel" and that the youth despair currently on display was "like an eruption of a volcano".

The suicides have been an especially troubling phenomenon, with shrines popping up at the locations where they happened and regular vigils.

But Yip warned against linking the deaths solely to politics.

"Studies have shown that people who killed themselves had suffered from multiple and interacting causes," he told AFP.

He said the tributes and memorials offered ways for people to express their emotions, which they should not suppress. But he warned that rhetoric characterising deaths by suicide as heroism or martyrdom risks other students taking their own lives.

After weeks of remaining silent on the issue, Hong Kong's government addressed the recent suicides on Friday evening with chief secretary Matthew Cheung saying they would mobilise NGOs to devote more time and resources to combating youth depression.

"We realise that many people are feeling unhappy at this present moment," he told reporters.

Hong Kong's suicide rate is around 12 per 100,000 -- higher than the World Health Organization's average for mainland China at eight per 100,000.

- 'Everyone counts' -

Amid the despairing tone of the recent protests, the city has also embraced open discussions of mental health, an often delicate subject in the largely conservative culture.

Two slogans -- "Every one of us counts" and "We go up and down together" -- have become rallying cries for mental health awareness.

Hong Kong enjoys rights unseen on the mainland, including freedom of speech, protected by a deal made before the city was handed back to China by Britain in 1997. But there are growing fears those liberties are being eroded.

Among recent watershed moments critics point to are the disappearance into mainland custody of dissident booksellers, the disqualification of prominent politicians, the de facto expulsion of a foreign journalist and the jailing of democracy protest leaders.

A government push to integrate Hong Kong further into mainland China has also led many to feel the city's unique Cantonese language and culture is being undermined.

Shai Dromi, a cultural and comparative-historical sociologist at Harvard University, said collective trauma is often tied to the loss of group identity.

"It really touches on fears of not being able to practise one's culture, one's rights, one's religion," he said.