Faced with joining a desperately long NHS waiting list, Joe Rackham opted for online counselling instead. “I just felt that I couldn’t wait any longer – I was motivated and ready to deal with my issues and quite liked the idea of doing so in the comfort of my own home,” said the 29-year-old, who lives in London. After an online search, he found a therapist whose profile suited his needs and booked a chat session for the next day.

Remote, text-based counselling is growing in popularity in the UK. The doctor app Babylon offers therapy to 150,000 active users, while PlusGuidance, an online counselling service, has 10,000 users. The US-based service BetterHelp also has 150,000 registered UK users (though not all are active). Talkspace, another online therapy platform, reports it has 500,000 registered users worldwide, with most in the US.

The websites allow members to find a therapist anywhere in the world. Sessions tend to be cheaper than face-to-face therapy – a 50-minute session on PlusGuidance typically costs around £40, depending on whether users opt for email, messaging or video calls.

“Therapists are independent service providers and they set their own prices,” said Nathaniel Smithies, founder of PlusGuidance. “We’re creating a marketplace that’s competitive and the prices come down so it’s cheaper. I don’t want to make it sound like eBay – it’s a marketplace business model, but we’re going a level above that to curate a high level of service.” He added that the site verifies all the therapists’ qualifications and provides additional training on how to work online.

It’s not hard to see why online counselling is growing in popularity. Tech is a part of modern life – especially for millennials, the biggest group of users on PlusGuidance – and NHS mental health services are overstretched.

Stephen Buckley, head of information at the mental health charity Mind, said: “As we raise awareness of mental health problems and more and more people come forward and seek the help they need, we see demand for NHS mental health services rising. Having been underfunded for decades, we know that services are struggling to cope.”

Experts are still learning about how online counselling compares with face-to-face therapy, with the anonymous nature of the internet being a big issue, said Terry Hanley, programme director of the doctorate in counselling psychology at Manchester University.

When researching young people’s experience of online counselling, however, Hanley found evidence of positive relationships between individuals and their therapists. “From my perspective that would be an indicator of good quality,” he said. “But then it’s difficult to say – they were reporting that it was beneficial, but if you measured them on a psychometric [test], whether or not that was the case would be another matter.”

If the person is in distress, there’s a lot of anxiety for the practitioner because you can’t see them Kate Anthony, therapist

One advantage of online therapy is the disinhibition effect, he added, where people feel more comfortable opening up and discussing problems when they are online. But there are concerns about the varying quality of online therapy, and the security of patients’ personal data.

“Counsellor” and “psychotherapist” are not protected titles, though there are a number of accredited registers, such as the British Association for Counselling and Psychotherapy (BACP), which indicates that therapists are qualified.

But Kate Anthony, BACP fellow and co-founder of the Online Therapy Institute, said that even among qualified therapists there is a lack of training about how to work online. “Training in the UK ignores the way we communicate in the modern world. They’re very much focused on face-to-face, talking therapies, which are great, but people think that because they use email they can just banter back and forth – there’s no awareness of the ethical issues. If the person is in distress, there’s a lot of anxiety for the practitioner because you can’t see them. They might log off and do something to harm themselves.”

Online training advises therapists on everything from using emojis to avoiding misinterpretations. They also need to protect patients’ personal data – an issue that has caused controversy in the US, where big online therapy platforms have come under the spotlight.

Buckley said patients should check services’ privacy policies before signing up. “Not all online counselling sites use professionally trained therapists or adhere to an ethics policy, so ask your GP for a recommendation in the first instance. As with all kinds of services and support, what works for one person may not work for someone else,” he said.

Marc Bush, chief policy adviser at Young Minds, said that while online counselling services are valuable, “they shouldn’t replace face-to-face therapy with a trained professional. If a young person is struggling, we would encourage them to talk to their GP in the first instance, or to contact an established service like The Mix, Childline or the Samaritans.”

For Rackham, who has generalised anxiety disorder, online counselling wasn’t the right fit. “I felt it was near impossible for the therapist to really get a sense of the issues I was dealing with, as all they had to go from was my typed-out words. I think I realised after that online session how crucial interpersonal interaction was.

“I’m a big fan of using technology in all areas of my life as a solution to everyday problems. I have apps for everything, but when it comes to mental health, you have to choose how technology plays a role in your recovery very carefully.”

The Samaritans can be called on 116 123. In the US, the National Suicide Prevention Hotline is 1-800-273-8255. In Australia, the crisis support service Lifeline is on 13 11 14.