Reiki: what it is, what the evidence shows and what to check before trying it

Sessions are usually quiet and take place with you lying or sitting, fully clothed. The practitioner rests their hands on or just above different parts of your body. Many people describe feeling relaxed, warm or sleepy afterwards. Cancer Research UK says practitioners recommend resting and drinking water after a session.

The explanation offered within reiki is that it helps balance energy fields in and around the body. This is a belief system rather than a measured physiological process, which matters when judging the claims made about it.

The National Center for Complementary and Integrative Health states that reiki has not been clearly shown to be effective for any health-related purpose. Studies have looked at pain, anxiety and depression, but most were not of high quality and the results were inconsistent.

It also notes that there is no scientific evidence supporting the existence of the energy field thought to play a role in reiki. That does not mean people never feel better after a session, only that any benefit cannot currently be attributed to the mechanism reiki describes. Relaxation, time set aside and attentive human contact may all play a part.

Cancer Research UK is direct on this point: there is no scientific evidence that reiki can prevent, treat or cure cancer, or any other disease. It adds that limited studies suggest possible modest benefits for anxiety and for pain after surgery in small groups of patients.

Some UK cancer centres and hospices offer sessions as a supportive extra. If you are having treatment, tell your oncology team about any complementary therapy, so that nothing conflicts with your care plan and you are not tempted to delay or stop treatment.

Reiki has not been shown to have any harmful effects, and because it involves no manipulation, needles, oils or ingested products, the physical risks are generally regarded as low. The real risk, as the NCCIH puts it, is relying on an unproven therapy instead of evidence-based medical care.

Be cautious of any practitioner who claims to cure disease, who tells you to stop prescribed medicines, or who discourages you from seeking a diagnosis. Persistent or worsening symptoms need a GP assessment, and sudden severe symptoms need NHS 111 or 999.

Reiki is not statutory regulated in the UK. Cancer Research UK advises looking for a practitioner with at least a Level 2 qualification, checking whether they are registered with the Complementary and Natural Healthcare Council, and looking at the UK Reiki Federation listing. The Council's register has been approved as an Accredited Register by the Professional Standards Authority, and reiki is among the professions it lists.

Accreditation tells you that a practitioner has met a register's standards on training, conduct and complaints. It does not tell you that reiki treats a disease.

• Ask about training level and how long they have practised.

• Ask what their register requires in insurance, conduct and continuing training.

• Ask what they would do if a client needed medical help during a session.