Instrument	Dimensions (subscales, no. of items)	Validated instrument	Answer options	Scores	Minimum score Maximum score	Weighting of scores	Direction of scales
	Diabetes Distress Scale (DDS)	17‐items with four subscales: emotional burden (EB) subscale (5 items), physician‐related distress (PRD) subscale (4 items), regimen‐related distress (RRD) subscale (5 items), and diabetes‐related interpersonal distress (DRID) subscale (3 items)	Yes	6‐point Likert‐scale from 'not a problem' to 'a serious problem'.	A total mean‐item score DRD (tDRD) scale score plus 4 subscale scores	Minimum score: 1 Maximum score: 6 A mean score of less than 2.0 indicates little to no distress, a score between 2.0 and 2.9 indicates moderate distress and 3.0 and greater is considered high distress worthy of clinical attention	No	Higher values mean higher distress
Fisher 2011	Baseline mean tDDS (SD): active control: 2.25 (0.88); structured testing: 2.41 (0.98) 12‐months mean tDRD (SD): active control: 1.93 (0.07); structured testing: 1.78 (0.06)
Fisher 2013	Baseline mean tDDS (SD): Leap Ahead: 2.48 (0.95); computer‐assisted self‐management (CASM): 2.37 (0.86); CAPS: 2.38 (0.89) 12‐months mean tDRD (SD): Leap Ahead: 1.98 (0.88); CASM: 2.03 (0.83); CASM + problem solving therapy: 1.92 (0.75)
Hermanns 2015	Baseline tDRD (SD): intervention: 2.7 (0.9) (); control: 2.7 (0.8) 12‐months tDRD (SD): intervention:3.4; control: 3.0
Liu 2015	Baseline mean tDDS (SD): peer education: 3.18 (0.2); usual education: 3.14 (0.9) 12‐months mean tDRD (SD): peer education: 2.67 (0.6); usual education: 3.02 (0.6)
Quinn 2011	Baseline mean tDDS (SD): usual care: 2.4 (0.9); group 2: 2.7 (0.9); group 3: 2.8 (0.7); group 4: 2.6 (0.9) 12‐month mean tDRD (SD): usual care: 2.3 (0.9); group 2: 2.6 (0.9); group 3: 2.4 (0.8)); group 4: 2.3 (0.8)
Glasgow 2005	No mean scores provided, just effect sizes
Trief 2016	Baseline mean tDDS (SD): diabetes education: 2.2 (0.9); individual calls: 2.3 (1.1); change couples intervention: 2.4 (0.8) (CC) 12‐months mean tDRD (SD): diabetes education: 2.2 (1.0); individual calls: 1.9 (1.0); change couples intervention 1.7 (1.0)
	Instrument	Dimensions (subscales, no. of items)	Validated instrument	Answer options	Scores	Minimum score Maximum score	Weighting of scores	Direction of scales
	Diabetes Distress Scale (DDS‐4)	4‐item with 2 items from the original 17‐item emotional burden (EB) subscale, and another 2 items from regimen‐related distress (RRD) subscale	Yes	6‐point Likert‐scale from 'not a problem' to 'a serious problem'.	A total mean‐item score	Minimum score: 1 Maximum score: 6	No	Higher values mean higher distress
Simmons 2015	Baseline (SD): Control (SD): 6.61 (4.05) 1:1 : 6.53 (4.12) Group (SD): 6.27 (3.22) Combined (SD): 6.71 (4.27)
	Instrument	Dimensions (subscales, no. of items)	Validated instrument	Answer options	Scores	Minimum score Maximum score	Weighting of scores	Direction of scales
	Problem Areas in Diabetes (PAID)	None (20 items)	Yes	5‐point Likert‐scale	Total score (TS)	Minimum score: 0 Maximum score: 100	No	Lower values mean better assessment
Beverly 2013	Baseline mean total score (SD): intervention: 33.3 (20.3); control: 34.8 (23.1) 12‐months mean total score (SD): intervention: 25.0 (16.0) (intervention)/ 25.7 (22.7)
Davies 2008	No baseline value was reported 12‐months mean total score: intervention: 14.1 (6.3‐28.1); control: 12.5 (4.7‐28.1)
Dennick 2015	Baseline mean total score (SD): intervention: 37.1 (2.5); control: 34.4 (2.3) Follow‐up mean total score (SD): intervention: 35.3 (1.4); control: 34.4 (1.6)
D'Eramo Melkus 2010	Baseline mean total score (SD): intervention: 54 (31); control: 60 (30) 24‐months mean total score (read from graph): intervention: about 38; control: 48
Gabbay 2013	The baseline mean total score was 29 for both groups. PAID scores did not differ significantly at year 1, at Year 2 the scores were better in the intervention compared with the control group.
Glasgow 2005	Mean total score (SD): baseline intervention (baseline control): 30.3 (28.5) Mean total score (SD): 12‐month intervention (12‐month control): 29.7 (26.8)
Grillo 2016	Baseline PAID score(SD): educational: 20 (14); control: 16 (13) 12‐month follow‐up (SD): decrease in the PAID score when compared to baseline (intervention: −34 (22) vs controls: —26 (18))
Hermanns 2015	Mean total score (SD): baseline intervention (baseline control): 39.7 (37.5) Mean total score (SD): 12‐month intervention (12‐month control): 48.5 (40.1)
Hermanns 2012	Baseline mean score (SD): intervention: 52.5 (9.2); control: 47.6 (9.6) Endpoint mean score (SD): intervention: 49.1 (9.7); control: 48.0 (11.2)
Lamers 2011	Baseline mean total score (SD): intervention: 22.6 (20.5); control: 23.4 (19.5) 9‐months mean total score (SD): intervention: 18.49 (1.76); control: 22.89 (1.72)
Lerman 2009	Baseline mean total score (SD): intervention 1: 45 (23) (GRT); intervention 2: 49 (29) (GCR); control: 51 (19) 12‐month mean total score (SD): intervention 1: 46 (26) (GRT); intervention 2: 38 (21) (GCR); control: 49 (23)
Pibernik‐Okanovic 2015	Baseline mean total score (SD): psychoeducation: 37.9 (19.7); physical exercise: 42.6 (20.5) (physical exercise); re‐education: 39.1 (19.6) 12‐month mean total score (SD): psychoeducation: 32.5 (22.1); physical exercise: 36.4 (22.1); re‐education: 33.2 (20.3)
Rosenbek 2011	Baseline mean total score (SD): intervention: 20.0 (17.7); control: 19.6 (16.3)
Shibayama 2007	Baseline mean total score (SD): intervention: 38 (28–52); control: 35 (26–51)
Skelly 2009	Changed score (SD): Intervention: 2.05 (0.56) Intervention with booster: 2.28 (0.83) Weight and diet: 2.31 (0.75)
Spencer 2013	12‐baseline (intervention): −12.1 (−16.3 to −6.0) 12‐baseline (delayed): −7.1 (−12.5 to 0.6)
Sperl‐Hillen 2013a	Mean total score at baseline: usual care: 30.52; individual education: 29.81 group education: 29.62 ()
Sturt 2008	Baseline mean total score (SD): intervention: 21 (15); delayed: 21 (15) 6 months mean total score (SD): intervention: 17 (14); delayed: 22 (17)
Taylor 2006	Baseline mean total score: cognitive: 38.2; wait‐list: 30.72; intervention: 30.35
Van der Wulp 2012	Mean total score (SD): Intervention group: T0: 16.65 (18.95); T1: 13.19 (12.90); T2: 12.74 (14.02) Control group: T0: 14.48 (15.50); T1: 12.17 (11.90); T2: 11.09 (14.99)
Van Dijk‐de Vries 2015	Mean total score (SD): Intervention group: T0: 29.9 (16.9); T12: 27.8 (16.5) Control group: T0: 28.9 (19.4); T12: 27.0 (19.7)
Weinger 2011	Baseline: Type 2 diabetes: 32.5 (1.3 to 73.8) Structured behavioural: 34.4 (2.5 to 91.3) Attention control: 30.0 (3.8 to 85) Individual control: 32.5 (0.0 to 80.0)
Welch 2015	Baseline mean total score (SD): intervention: 59.0 (30.5); control: 51.9 (32.3) 6 months mean total score (SD): intervention: 40.4 (2.1); control: 48.3 (2.0)
Whittemore 2004	Baseline mean total score (SD): intervention: 59.9 (22); control: 42.3 (14) 6‐months mean total score (SD): intervention: 46.9 (23); control: 42.9 (19)
aOne PAID question was inadvertently omitted on the survey resulting in a PAID score based on 19 instead of 20 questions.