Effects of a theory-based smartphone intervention to decrease neuroticism in the general public

Many people wish to be less neurotic, but evidence about neuroticism interventions with potentially wide-ranging benefits is limited. We conducted a 6-week, digital intervention with multiple treatment groups and a randomized control design (N = 426) to examine the efficacy of theory-based strategies that varied in scope, intensity, and content. Across groups, participants decreased on self-report and implicit neuroticism measures (d = -0.18 to -0.38). Intervention effects exceeded normative change and demand effects, were specific to neuroticism, and persisted at 2-month follow-up (d = -0.14 to -0.43). Efficacy was proportional to treatment intensity and specificity (d = -0.16 to -0.60), and there was some evidence that state-based strategies have stronger immediate effects whereas habit-based strategies have more enduring effects. This study demonstrates that motivated people can become meaningfully less neurotic with effort in just 6 weeks and offers insights into underlying mechanisms.