"Bibliotherapy" has been soaring in popularity as a means of improving people's wellbeing. But getting it right depends on the book, and the person.

In the summer of 2017, Elizabeth Russell was going through a rough patch. It was during a difficult divorce, involving her two young teenagers, while she was still in the throes of a long-term depression. "It was just a really, really stressful time," recalls Russell, a teacher and librarian at an elementary school in Connecticut, US.

But then on the internet she came across something called "creative bibliotherapy", where a tailored recommendation of fiction is offered with the aim of improving mental health. The name Ella Berthoud, a bibliotherapist based in Sussex, UK, who co-wrote the book The Novel Cure about such literary remedies, kept popping up. Russell – an avid reader – immediately wanted to try it out.

After quizzing Russell on her reading habits and interviewing her about her challenges, Berthoud sent her a list of book recommendations relevant to her life, many featuring characters navigating tough marital decisions, like George and Lizzie by Nancy Pearl. "I just was blown away," Russell recalls. Learning from the lessons and mistakes of fictional characters helped her process what she was going through and made her feel less alone. "It opened up something in me that needed to be opened and needed to heal," she says.

In the UK and elsewhere, bibliotherapy – which also includes recommendations for non-fiction and self-help literature – has been soaring in popularity as a means of improving people's wellbeing, help navigate tough life decisions, and even to treat specific mental health conditions. (Read the BBC's book recommendations on homesickness and resilience.)

While the benefits of self-help literature are well documented, advocates of fiction-based or "creative bibliotherapy" claim similar advantages. They argue that immersing oneself in rich, simulated worlds – often reflective of real-life experiences – can help readers process emotions, discover coping strategies, or simply provide momentary escape from their everyday woes.

As two researchers wrote in a 2016 paper in The Lancet, immersion in great literature can "help relieve, restore, and reinvigorate the troubled mind – and can play a part in relieving stress and anxiety, as well as other troubled states of mind". Considering the shortage of affordable mental health services in many countries, the idea that fiction can offer support is appealing.

As anyone who has ever read and loved a work of drama, poetry or fiction can attest, stories have powerful effects on our minds and emotions. But that doesn't mean that any kind of fiction boosts mental health for everyone. Several experts interviewed for this article worry about what they see as an overhyped promise of creative bibliotherapy in treating specific mental health conditions, where they say the scientific evidence is still rather thin. In fact, research suggests that certain books can even be harmful.

Rather, the existing research paints a more nuanced picture, suggesting that fiction can help boost general wellbeing, but it depends a lot on the person, the book and how they engage with it, says James Carney, a computational cognitive scientist at the London Interdisciplinary School.

"There's this idea that books are this cultic object that are going to make everything better," Carney says. "I think for a certain number of conditions and for a certain type of personality, it can be the case, but the idea that they're a universal medicine is just simply false."

Some trace the origins of bibliotherapy to World War One, when fiction and non-fiction books were used to ease soldiers' suffering and trauma. But the idea made a return in the 1990s, Carney says. Today it takes many forms – from bibliotherapists like Berthoud who offer tailored recommendations for £100 ($130) per session, to some GPs who point some of their patients to fiction, like Andrew Schuman. He's an NHS physician who advises the bibliotherapy charity ReLit and co-wrote the 2016 Lancet paper about the benefits of bibliotherapy.

While fiction bibliotherapy isn't a substitute for other treatments, "in conjunction with other therapies, it can be a massively powerful, boosting therapy", Schuman says. A benefit compared with other therapy types, Russell adds, is that people can do it on their own time, approaching their books when they feel emotionally ready and putting them down if they're overwhelmed.

Since 2013, the UK non-profit The Reading Agency's Reading Well programme has been curating book lists for people with conditions like dementia or depression. These lists are hand-picked and reviewed by experts and people with lived experiences of those conditions,

© BBC