People with back pain who have low expectations of acupuncture before they start a course of treatment will gain less benefit than those who believe it will work, according to new research.

Additionally, people who have a positive view of back pain and who feel in control of their condition experience less back-related disability over the course of acupuncture treatment.

The University of Southampton's Dr Felicity Bishop, an Arthritis Research UK career development fellow, carried out the research to find out why some people with back pain gain more benefit from acupuncture than others.

The findings of the study, which has been funded by Arthritis Research UK, are published in The Journal of Clinical Pain.

Dr Bishop said: "The analysis showed that psychological factors were consistently associated with back-related disability.

"People who started out with very low expectations of acupuncture - who thought it probably would not help them - were more likely to report less benefit as treatment went on.

"When individual patients came to see their back pain more positively they went on to experience less back-related disability.

"In particular, they experienced less disability over the course of treatment when they came to see their back pain as more controllable, when they felt they had better understanding of their back pain, when they felt better able to cope with it, were less emotional about it and when they felt their back pain was going to have less of an impact on their lives."

Acupuncture is one of the most established forms of complementary therapy. Recommended in clinical guidelines, there is evidence from clinical trials to show that it can help to reduce pain, Dr Bishop said.

Previous research has established that factors other than the insertion of needles play a part in the effectiveness of acupuncture, such as the relationship the patient develops with the acupuncturist and the patient's belief about acupuncture.

Dr Bishop recruited 485 people who were being treated by acupuncturists for the study, and they completed questionnaires before they started treatment, then two weeks, three months and six months later. The questionnaires measured psychological factors, clinical and demographic characteristics and back-related disability.

Dr Bishop suggested that to improve the effectiveness of treatment, acupuncturists should consider helping patients to think more positively about their back pain as part of their consultations.

Dr Stephen Simpson, director of research at Arthritis Research UK, said: "This study emphasises the influence of the placebo effect on pain. The process whereby the brain's processing of different emotions in relation to their treatment can influence outcome is a really important area for research.

"Factors such as the relationship between practitioner and the patient can inform this and we should be able to understand the biological pathways by which this happens. This understanding could lead in the future to better targeting of acupuncture and related therapies in order to maximise patient benefit."