Table 2.

Summary of habit strength, medication adherence measures, and outcomes in the included studies.

Source	Habit strength measure	Adherence scale and rates	Relationship between habit strength and adherence rates
Bolman et al [16]	SRHIa	MARSb	Correlation r=0.61; P<.001
Burns et al [14]	Self-report behavioral automaticity index	Did you ever forget to take your medication? on a 5-point scale	Depressive symptoms: beta=.08; P<.001; 95% CI 0.04 to 0.12 Diabetes distress: beta=.09; P<.001; 95% CI 0.04 to 0.12 Major depressive syndrome: beta=.07; P<.001; 95% CI 0.03 to 0.11
Durand et al [19]	Self-report behavioral automaticity index	Overall adherent range: 58.9%-79.7% MARS: 36.7% nonadherent MMASc: 41.1% nonadherent Prescription refill: 79.7% adherent Urine assay Total nonadherence, 2.1% Partial nonadherence, 23.8%	MARS: correlation r=0.36d; P<.001 MMAS: correlation r=0.35d; P<.001 Prescription refill: correlation r=0.08 Urine assay: correlation r=−0.02 Adherence composite: correlation r=0.36; P<.001 Hierarchical regression analysis: beta=.44; P<.001; adjusted. R2=0.22, ΔR2=0.19; ; P<.001 Unintentional adherence: beta=−.45; t203=−7.04; P<.001 Intentional adherence: beta=−.22; t203=−3.08; P<.01
Guenette et al [8]	SRHI About 71% scoring high (at least 5/6) Mea	MMAS-8 modified French version 45% high adherence 40.7% medium adherence 14.3% low adherence	Adjusted ORe 1.65; 95% CI 1.35 to 2.03; P<.001
Hooa et al [10]	Multiplicative product of behavior frequency and context stability	Electronic pill bottles 47.30% median adherence 4.9% low adherence 80.5% variable adherence 14.6% high adherence	Overall cohort: R=0.40; 95% CI 0.36 to 0.44; beta=.30; 95% CI −1.04 to 1.65 Adherence consistently low: R=0.24; 95% CI 0.04 to 0.44; beta=3.03; 95% CI −9.68 to 15.76 Variable adherence: R=0.45; 95% CI 0.41 to 0.49; beta=.08; 95% CI −1.44 to 1.60 Adherence consistently high: R=0.20; 95% CI 0.13 to 0.27; beta=.61; 95% CI −1.90 to 3.13
Hoob et al [9]	Self-report behavioral automaticity index	Chipped nebulizer 75.4% low adherence 13.1% medium adherence 11.5% high adherence	Median habit strength in different subgroups: Low adherence: 9.0, IQR 4.8-12.0 Moderate adherence: 14.5, IQR 11.3-18.3 High adherence: 18.0, IQR 14.0-20.0 All significantly correlated with adherence levels, P<.001
Murphy et al [20]	Self-report behavioral automaticity index Mean habit strength per number OCPf missed per month	MARS Mean MARS score per number of OCP missed per month: Never: 5.85 Once: 7.49 Twice or more: 10.12	Correlation r=−0.24g; P<.001
Phillips et al [7]	Self-report habit index, with 4 additional questions	MARS, MMAS, MEMSh Mean adherence MMAS=0.80 MEMS timing adherence=76% MEMS dosing adherence=96%	Bivariate relationship (correlations): MARS: 0.37 MMAS: 0.26 MEMS dose frequency: 0.42 MEMS dose timing: 0.49 Hierarchical regression analysis: MARS: ΔR2=0.11; P<.01 MMAS: ΔR2=0.06; P=.04 MEMS frequency: ΔR2=0.17; P<.001 MEMS timing: ΔR2=0.27; P<.001 Unintentional nonadherence: beta=−.32; t66=−2.55; P=.01 Intentional nonadherence: beta=−.23; t66=−1.82; P<.07
Phillips et al [21]	Self-report behavioral automaticity index Mean medication-taking habit strength 3.75	MARS and MEMS Mean adherence: MARS=4.66 Self-reported intentional nonadherence=1.24 Self-reported unintentional nonadherence=1.76 MEMS % days adherent=76.19 MEMS % doses on time=60.68	Bivariate correlations: MARS: 0.40, P<.001 Self-reported intentional nonadherence: −0.34; P<.001 Self-reported unintentional nonadherence: −0.41; P<.001 MEMS % days adherent: 0.37; P<.001 MEMS % doses on time: 0.40; P<.001 MARS (with control variables): beta=0.15; β=.32; P<.001 MEMS (with control variables): beta=8.57; β=.32; P<.01
Thorneloe et al [22]	Self-report habit index Mean 41.5 for self-administered systemic therapy	MARS Overall: 22.4%, nonadherent 12% intentional 10.9% unintentional Conventional: 29.2% overall 15.3% intentional 14.5% unintentional Biologic: 16.4% overall 9.1% intentional 7.7% unintentional	Multivariable regression model: 0.94 overall nonadherence: 95% CI 0.91 to 0.97 0.95 intentional nonadherence: 95% CI 0.92 to 0.98 0.92 unintentional nonadherence: 95% CI 0.89 to 0.96
Voils et al [23]	Product of frequency and mean of 5 situational consistency items	Patient rating and MMAS-8 60% nonadherent	Extent of nonadherence: correlation r=−0.39; P<.001

^aSRHI: self-report habit index.

^bMARS: medication adherence report scale.

^cMMAS: Morisky medication adherence scale.

^dZ-scores averaged. So greater MARS and MMAS scores represented greater nonadherence.

^eOR: odds ratio.

^fOCP: oral contraceptive pill.

^gNegative because lower MARS score represents better adherence.

^hMEMS: medication event monitoring system.