Nicole enters the therapist’s room and clutches what she calls her hugging pillow. She admits to being nervous about sitting down with a stranger to discuss her mental health.

She is 31, lives in London and works as chiropractic assistant. She suffers from anxiety when she drives.

“There are so many things that so quickly go through my head,” she says.

“How far away is it? What is the route? I somehow forget how to drive.”

She suffers from panic attacks and her fear of driving means she is constantly cancelling plans.

But, over the course of six sessions with psychotherapist Owen O’Kane, it becomes clear her problems are much deeper than just a fear of driving.

Every week, one in six of the UK population experience mental health problems such as depression and anxiety and every year more than 1.2 million people seek help from the NHS talking therapies service, with many more paying for support privately.

This form of therapy is most commonly used for anxiety and depression, but can also help with a range of other problems, including body image dysmorphia, obsessive compulsive disorder and post traumatic stress disorder. It does not work for everyone: research suggests one-third of people do not benefit.

The BBC has followed 12 people, featured in the series Change Your Mind, Change Your Life, who each received six support sessions from therapists.

The therapists have used a combination of different talking therapy approaches, including cognitive behavioural therapy which focuses on changing the way we think and behave, alongside other techniques to improve relationships and process trauma.

What it reveals is striking: How understanding and learning to manage the mind has the power to transform lives.

“You’re not stuck with the brain you’ve got,” says Owen O’Kane, who has worked in the field for 25 years.

He describes his job as like detective work: “People come with what seems to be a reasonable story, but the interesting thing is that very often the story and emotions don’t match. I guess what we are doing is digging around a little bit.”

Over their sessions, Owen digs deeper into Nicole’s anxiety. At one point she weeps. She admits in the past she has “completely hated” herself. She worries about what people think of her and is socially anxious: “I don’t feel good enough to be there. I might say something wrong. I need people to like me.”

Owen questions why she feels like this: “As human beings we like the nice emotions. We like feeling happy, joy, being in love.” but he says some people try to avoid or suppress emotions like fear, dread and sadness, and that can cause anxiety. Instead, he says it is healthier to accept them and accept them as safe.

When people get to that point, he says, they start to feel empowered: “They realise they’re not going to be overwhelmed.”

Speaking outside the therapy room, Nicole says: “I’m shocked. He got my number straight away. I would see vulnerability as a negative thing, but it’s not.”

Asked to describe herself she uses words such as kind, thoughtful, determined and enthusiastic: “I am not a bad person,” she tells Owen.

She says she has learned a lot: “Most importantly I found I wasn’t being kind to myself. That was really eye-opening.”

Owen says this is typical of many people he treats: “When people get to these crossroads, when they wake up and realise what they are doing, that’s a gold dust moment for me.”

James likewise learned to think about himself differently thanks to therapy.

A 39-year-old father-of-one who works in finance, he struggles with anxiety and, in particular, worries about making mistakes at work. That fear is so debilitating he doesn’t make it to work sometimes.

He has been supported by Prof Steve Peters, a psychiatrist who explains perfectionism is at the root of his problems: “If we think it’s the end of the world if we make a mistake, it paralyses you.”

James was once an athlete, playing semi-professional football and competing in athletics before specialising in the bobsleigh.

He was training for trials for the Great Britain team when he had a stroke eight years ago: “With a flick of a switch, I lost everything,” he says.

“It made me feel a lesser man.”

Now he fears under-performing at work and losing his job.

Over the course of the sessions, Prof Peters explains the key is James’s belief system.

First, he gives some seemingly simple advice: “Put your feet on the floor, stand up and walk,” he says.

Focusing on the basic task of moving, in James’s case moving so he can get to work, enables someone caught up in catastrophic thinking to block out the negative thoughts that stop them doing something.

In later sessions, James and Prof Peters explore what could be behind his problems. James tells Prof Peters about his childhood and how his father would criticise him to push him to improve.

Prof Peters explains how James believes that to please you cannot make errors and then the devastating stroke he suffered at a young age has triggered an absolute desire for things to never go wrong again.

He tells James he needs to make “peace with himself” by defining himself not by performance but by values and behaviours. He too asks James to describe himself and James replies he is hard-working, honest, engaging, friendly and as someone who would put others first.

Over the course of his sessions, James’s way of thinking changes: “I can look at myself in the mirror and feel my value and my worth,” he explains.

Anjalee’s struggles are somewhat different. They relate to one traumatic event in childhood – her mother died suddenly when she was 15.

Now a mother herself, with three children under five, she has struggled emotionally.

She has sleepless nights, a tight chest and feels emotionally disconnected. It is worse than any physical pain, says the 34-year-old: “Becoming a mother has reopening everything I’ve tried to suppress.”

Her first birth was particularly traumatic. She developed sepsis – the condition her mother died from: “I thought I was not going to survive,” she says.

Her psychotherapist, Julia Samuel, explains to Anjalee she has not been able to process what has happened and, as a result, the trauma has stayed with her.

When her mother died, Anjalee was in the middle of exams and had two younger siblings, leaving her without time to grieve.

Julia suggests eye movement desensitisation and reprocessing therapy, which uses movement to help people process and recover from distressing events.

Julia asks Anjalee for her worst memory and she describes how her father tried to save her mother’s life by performing chest compressions in their home until the paramedics arrived. Her mother was rushed out with Anjalee hoping she would return. She never did.

Anjalee says she has never talked about this within anyone. Julia asks Anjalee to cross her arms against her chest and start deep breathing and tapping, mimicking a butterfly’s wings flapping. She talks through the memory and how the images in her head are changing to more positive ones.

Julia says this type of treatment is particularly effective when dealing with one single traumatic event. One memory, she says, can act as a block on everything.

Afterwards, Anjalee speaks about how her symptoms have eased and the contentment she now feels.

“My therapist helped me reconnect with the 15-year-old girl I’d silenced. I began to process the trauma that haunted me. I now understand grief as the other side of love.”

During May, the BBC is sharing stories and tips on how to support your mental health and wellbeing.

Visit bbc.co.uk/mentalwellbeing to find out more.