Chronic musculoskeletal pain is a complex medical condition. Patients often experience increased levels of pain-related distress, including anxiety, depression and disability, impaired sleep, poor well-being and diminished quality of life. Over the past decade, numerous studies have provided evidence for the existence of attentional bias towards pain-related information in chronic pain patients. A critical question remaining unanswered is whether pain-related bias is simply an epiphenomenon of chronic pain, or whether it has a causal role in the maintenance of pain. Recently, there has been growing interest in the potential benefits of attentional retraining in individuals with various emotional disorders, with focus upon attentional bias modification (ABM).

ABM is a theory-driven intervention which uses computer-based paradigms, typically the visual-probe task, to implicitly manipulate attention away from sources of threat relevant to the individual's fears or concerns. To date, three published studies using ABM with chronic pain patients exist, the combined results of which support the therapeutic benefits of ABM on pain, pain-related distress and disability. Considering these encouraging results, it is important to expand this field of research and explore ABM in chronic pain in greater depth. In particular, all former studies assessed the clinical effectiveness of ABM in laboratory environments. The purpose of this double-blind RCT study is to determine whether internet-delivered ABM training (I-ABMT) has therapeutic benefits for patients with chronic musculoskeletal pain on pain and pain-related distress, thereby assessing training effects in real-world settings.

The visual-probe task will be used for assessment and modification of pain-related attentional biases. This is a computerised paradigm which records participant response times to a series of visual stimuli. Following an initial fixation point, each trial presents a stimulus pair in distinct locations (e.g. left and right of the initial fixation point), for a specified length of time (i.e., 500 or 1250ms). Stimuli may consist of words or images, with experimental trials featuring one pain-related stimulus and one neutral stimulus. Following this, both stimuli are removed, with a visual probe replacing one stimulus. Participants indicate the location of this probe as quickly and accurately as possible via manual response. Response times are faster to probes appearing in an attended region of the screen than an unattended region, providing a measure of attentional allocation. Averaged response times are calculated, which are converted into an index of attentional bias. In the standard and control (i.e., placebo) versions of the visual probe task, the probe replaces pain-related and neutral stimuli an equal number of times, while in the I-ABMT version, the probe always replaces neutral stimuli thus training attention away from pain-related stimuli.

Dose effects will be explored in this study, with participants randomised to one of four conditions: (i) 10-session Attentional Modification Group , (ii) 10-session Attentional Control Group, (iii) 18-session Attentional Modification Group, and (iv) 18-session Attentional Control Group. The primary outcome measures are pain intensity and pain interference, and secondary outcome measures include anxiety, depression, pain-related fear and sleeping impairment, including engagement to and satisfaction with the online visual-probe training task. It is hypothesized that participants receiving ABM training will show significantly greater reductions in pain and pain-related distress compared to participants receiving placebo training. Dose effects will be investigated in an exploratory manner, and data will be analysed and reported separately for participants aged 16 - 24 and 25 - 60.