Geschwind 2015.

Study characteristics
Methods	Study design: RCT Study grouping: parallel group Unit of randomisation: individuals Power (power sample size calculation, level of power achieved): not specified Imputation of missing data: not specified
Participants	Country: Belgium Setting: laboratory (sound‐attenuated and dimmed experimental room) Age: mean = 19.35 (SD = 1.98) years Sample size (randomised): 50, including 37 psychology students Sex: 50 women Comorbidity (mean (SD) of respective measures in indicated, if available) at baseline: not specified Population description: healthy women Method of recruitment: recruited from psychology students at University of Leuven (n = 37) + healthy volunteers (n = 13) Inclusion criteria: not specified Exclusion criteria: 1) being pregnant; 2) having respiratory or cardiovascular diseases, neurologic diseases (e.g. epilepsy), or any other minor or major illness, including chronic pain; 3) uncorrected hearing problems; 4) pain at the dominant hand or wrist Attrition (withdrawals and exclusions): for positive and negative affect: 8 missing at follow‐up; unclear for other outcomes Reasons for missing data: not specified
Interventions	Intervention: positive affect induction (BPS) (n = 25) delivery: individual setting; writing and visualisation providers: experimenter in laboratory setting duration of treatment period and timing: approximately 20 minutes description: participants asked to first think about (1 minute) and subsequently write about a future in which everything goes well and in which they realise their dreams (15 minutes) and then to visualise this scenario for 5 minutes compliance: not specified integrity of delivery: not specified economic information: 37 psychology students of the University of Leuven received course credits, and 13 volunteers were paid EUR 15 theoretical basis: BPS previously shown to selectively increase optimism, positive affect, and positive future expectancies, but not to decrease negative affect in pain‐related experiments; Peters 2010 Control: attention control (Typical Day) (n = 25) delivery: individual setting; writing and visualisation providers: experimenter in laboratory setting duration of treatment period and timing: approximately 20 minutes description: participants asked to first think about (1 minute) and subsequently write about a typical day (15 minutes) and then to visualise this scenario for 5 minutes (equivalent instructions) compliance: not specified integrity of delivery: not specified economic information: 37 psychology students of the University of Leuven received course credits, and 13 volunteers were paid EUR 15 theoretical basis: not specified; previously used in similar studies (e.g. Peters 2010)
Outcomes	Outcomes collected and reported: pain‐US expectancy ‐ single item self‐reported fear of movement‐related pain ‐ single item Positive and negative affect (modified Differential Emotions Scale; mDES) also assessed before/after affect induction, but not stated as dependent variables Time points measured and reported: 1) pre‐intervention, during acquisition phase (pain‐US expectancy, fear of movement‐related pain; rated after every 4th block in acquisition phase); 2) pre‐intervention (before affect induction phase; mDES); 3) post‐intervention (after affect induction phase; mDES); 4) post‐intervention, during test of generalisation (pain‐US expectancy, fear of movement‐related pain; rated before each movement); 5) post‐intervention, during transfer‐of‐acquisition phase (pain‐US expectancy, fear of movement‐related pain every other block); 6) 20‐minute follow‐up (mDES; after test of generalisation, approximately 20 minutes after affect induction) Adverse events: not specified
Notes	Contact with authors: We contacted authors to ask for the subgroup (summary outcome) data for psychology students, but they had not responded at the time of writing Study start/end date: not specified Funding source: Ann Meulders (AM) is a postdoctoral researcher of the Research Foundation Flanders (FWO‐Vlaanderen), Belgium (12E33714 N). The participation of Nicole Geschwind was made possible by the Center for Excellence on Generalization research, Katholieke Universiteit (KU) Leuven, Belgium (GRIP*TT; KU Leuven grant PF/10/005). The study was also supported by the Odysseus Grant ‘‘The Psychology of Pain and Disability Research Program’’ funded by the Research Foundation Flanders (FWO‐Vlaanderen), Belgium to Johan WS Vlaeyen (G090208N) and by an EFIC‐Grunenthal Research Grant (E‐G‐G ID: 169518451) to AM. Declaration of interest: The authors report no conflict of interest Ethical approval needed/obtained for study: approved by the Ethical Committee of the Faculty of Psychology and Educational Sciences of the University of Leuven (registration number: S‐54568) and the Medical Ethical Committee of the University Hospital of the University of Leuven (registration number: ML8513) Comments by authors: supplementary data related to this article can be found at dx.doi.org/10.1016/j.jpain.2014.12.003 Miscellaneous outcomes by the review authors: not relevant Correspondence: Nicole Geschwind, Department of Clinical Psychological Science, Maastricht University, Maastricht, The Netherlands; Corresponding author: Ann Meulders PhD, Department of Psychology, University of Leuven, Tiensestraat 102, Box 3726, 3000 Leuven, Belgium; ann.meulders@ppw.kuleuven.be
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Quote: "Participants were randomly allocated to either the PA induction group (n = 25) or the control group (n = 25), stratified by hand preference (left/right)." Judgement comment: insufficient information about random‐sequence generation to permit judgement of ‘Low risk’ or ‘High risk’; verified baseline comparability (see Supplementary Table S1) between groups in sociodemographic characteristic (age), variables related to pain‐US (physical stimulus intensity, duration of pain‐US) and positive affect before affect induction phase; significant difference in self‐reported stimulus intensity at calibration; baseline comparability for outcome variables (self‐reported fear of movement‐related pain, pain‐US expectancy) that were also assessed in acquisition phase before affect induction unclear
Allocation concealment (selection bias)	Unclear risk	Judgement comment: insufficient information about allocation concealment to permit judgement of ‘Low risk’ or ‘High risk’
Blinding of participants and personnel (performance bias) Subjective outcomes	High risk	Judgement comment: blinding of participants unclear; blinding of study personnel probably not done (experimenter who provides the intervention next to laboratory of participants, verbal communication and observation possible) and the outcome is likely to be influenced by lack of blinding
Blinding of outcome assessment (detection bias) Subjective outcomes	Unclear risk	Judgement comment: insufficient information about blinding of outcome assessment to permit judgement of ‘Low risk’ or ‘High risk’
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Quote: "Participants were randomly allocated to either the PA induction group (n = 25) or the control group (n = 25)" Quote: "FU measures were available only in a subset of 42 participants." Judgement comment: see supplementary material 1 (Increase PA after affect induction phase (post‐test)) for results for positive affect, 50 analysed; insufficient reporting of attrition/exclusions to permit judgement of ‘Low risk’ or ‘High risk’ (e.g. unclear how many participants were analysed for single outcomes)
Selective reporting (reporting bias)	Low risk	Judgement comment: no study protocol available but it is clear that the published reports include all expected outcomes, including those that were prespecified