People who stutter are being given electrical brain stimulation in a clinical trial aimed at improving fluency without the need for gruelling speech training.

If shown to be effective, the technique – which involves passing an almost imperceptible current through the brain – could be routinely offered by speech therapists.

“Stuttering can have serious effects on individuals in terms of their choice of career, what they can get out of education, their earning potential and personal life,” said Prof Kate Watkins, the trial’s principal investigator and a neuroscientist at the University of Oxford.

About one in 20 young children go through a phase of stuttering, but most grow out of it. It is estimated that stuttering affects about one in 100 adults, with men about four times more likely to stutter than women.

In the film The King’s Speech, a speech therapist uses a barrage of techniques to help King George VI, played by Colin Firth, to overcome his stutter, including breathing exercises and speaking without hearing his own voice. The royal client also learns that he can sing without stuttering, a common occurrence in people with the impediment.

Speech therapy has advanced since the 1930s, but some of the most effective programmes for improving fluency still require intensive training and involve lengthy periods of using unnatural-sounding speech.

The latest treatment, which is combined with fluency training, is not expected to completely cure people of their stutter but could potentially give them more control over it.

The brain stimulation, known as transcranial direct current stimulation (tDCS), involves strapping electrodes on each temple and then passing a current through the head. The current is weak enough that people are either oblivious to the electrodes being switched on or feel just a slight tingling.

The stimulation increases the firing rate of neurons in certain brain regions, which scientists believe could make it quicker to learn thought patterns associated with fluent speech, and make the effects of training more permanent.

There has been growing interest in the potential for tDCS to be used therapeutically for conditions ranging from depression to stroke, and some claim it could boost cognition in healthy people.

Watkins, who has been researching the causes of stuttering for more than a decade, is investigating whether tDCS could help shift the patterns of brain activity that occur during speech towards resembling those that occur in people who speak fluently. Previously, her team has shown that stuttering is linked to subtle differences in brain activity, including more activity than usual in the brain’s right hemisphere.

In the trial, the 40 participants are asked to speak in time with a metronome, saying one syllable on every beat. During this task, people who stutter typically become completely fluent.

“The idea is that if you stimulate them while they’re fluent, you’re reinforcing that fluent speech process,” said Jennifer Chesters, a speech and language researcher at the University of Oxford who is involved in the trial. “And hopefully that will make it more likely for them to use that process in their normal life.”

Each time a neuron fires in the brain, its connections with neighbouring neurons are strengthened or weakened slightly – this is how learning occurs. With stimulation, the threshold for neurons firing is lower, so this could accelerate the rewiring that occurs during fluency training.

Half of the participants – all men with moderate to severe stutters – are given electrical stimulation while doing this task for 20 minutes. The rest wear the electrodes without them being switched on as a control. The participants repeat the training every day for five days, and their speaking fluency is tested at the outset, at each session and at a follow-up three months later.

Case study: ‘It’s like a wall you can’t see over’

Facebook Twitter Pinterest Researcher Jennifer Chesters fitting electrodes to Naheem Bashir’s head. Photograph: Martin Godwin/The Guardian

Naheem Bashir, 28, a neuroscientist based in London, is one of the trial’s participants. As a teenager, Bashir struggled to cope with his stutter and was thrown into crisis at the prospect of leaving home and going to university. “I felt I wouldn’t be taken seriously, I wouldn’t be able to make friends,” he said. “I felt so limited and restricted. My mental health really took a hit.”

Bashir had speech therapy, which he said gave him some strategies for controlling his stuttering but more importantly helped him process his anxiety around it. “It’s realising that 99.9% of what we imagine will happen won’t happen,” he said.

Bashir has recently completed a PhD looking at how the brain processes speech, runs a British Stammering Association support group for people who stutter, and sometimes does stand up comedy. He wants to break down the social stigma around stuttering, but there are still moments when not being able to get his words out is frustrating.

“Using the phone is one of the most difficult things,” he said. “The other person is saying ‘the signal’s breaking up, I can’t hear you,’ and you’re like: ‘No, I’m literally not speaking,’” he said.

The unpredictability of how fluent their speech will be at any given time is also a challenge for many people who stutter. During an interview with the Guardian, Bashir’s speech was almost flawless, but in a fluency test he repeatedly got held up on words read aloud from a sample text.

Bashir is no longer desperate for a cure but he said better treatments could still be transformative. “When you’re in your worst moments of your stammer, it’s like a wall that you can’t see over,” he said. “Things like this intervention, if it works, can help bring down those walls a bit, so your stammer doesn’t feel as much of an obstacle and so you can see a life beyond your stammer.”

More information on the trial, which is still recruiting participants, can be found here