The Lightning Process (LP) is a three-day personal training programme developed and trademarked by British osteopath Phil Parker. It claims to be beneficial for various conditions, including chronic fatigue syndrome, depression and chronic pain. Developed in the late 1990s, it aims to teach techniques for managing the acute stress response that the body experiences under threat. The course aims to help recognise the stress response, calm it and manage it in the long term. It also applies some ideas drawn from neurolinguistic programming (a pseudoscience), as well as elements of life coaching. A clinical trial in 2017 found that Lightning Process was effective when added to treatment for chronic fatigue syndrome, but it is not recommended by the NHS. Two corrections of this article were published due to methodological weaknesses. The approach has raised some controversy due to using psychological techniques to cure a physical illness. The website was amended after the Advertising Standards Authority ruled that it was misleading. In 2021, after a review of the available evidence, the National Institute for Health and Care Excellence explicitly advised against the use of Lighting Process among patients with chronic fatigue syndrome. Description The Lightning Process comprises three group sessions conducted on three consecutive days, lasting about 12 hours altogether, conducted by trained practitioners. According to its developer, Phil Parker, the programme aims to teach participants about the acute stress response the body experiences under threat. It aims to help trainees spot when this response is happening and learn how to calm it. Techniques based on movement, postural awareness and personal coaching are intended to modify the production of stress hormones. Participants practise a learnt series of steps to habituate the calming method. The Lightning Process is based on the theory that the body can get stuck in a persistent stress response. The initial stressor may be a viral or bacterial infection, psychological stress, or trauma, which causes physical symptoms due to the body's stress response. These symptoms then act as a further stressor, resulting in overload of the central nervous system and chronic activation of the body's stress response. Neuroplasticity then causes this abnormal stress response to persist and be maintained. The Lightning Process suggests that while this disruption initially happens at an unconscious level, it is possible for the patient to exert conscious control and influence over the process, eventually breaking the cycle. The rationale for the programme draws