Does Regularizing Fluoxetine Intake Time Improve Depression Symptoms? A Single-Subject Study

Keywords: Fluoxetine, Antidepressant timing, Intake regularity, Depression, Single-subject study, N-of-1 trial, Mood, Energy, BDI-II, Self-tracking, Personal science

TL;DR: Regularizing the clock time of fluoxetine intake in a single-subject study did not improve mood or energy.

Abstract: We evaluated whether taking fluoxetine at a more consistent clock time improves depression symptoms for a single 35-year-old male with diagnosed depression, autism spectrum disorder and ADHD. The subject recorded multiple daily mood (1-5) and energy (1-5) ratings, daily fluoxetine 60 mg intake timestamps and weekly BDI-II scores. Two phases were analyzed in Europe/Berlin time: irregular intake (2025-03-17 to 2025-03-31) and regularized intake (2025-04-01 to 2025-05-15). Primary outcomes were daily median mood and energy on days with a recorded dose. Intake regularity increased (circular SD 0.87 vs 0.39 rad; difference 0.48 rad, 95% CI [-0.15, 1.14]). Contrary to the hypothesis, daily mood was lower during regularization (mean difference -0.46; Hedges g -0.59, 95% CI [-1.68, 0.30]; permutation p=0.095). Daily energy showed little change (difference -0.08; g -0.11, 95% CI [-0.77, 0.47]; p=0.809). Exploratory BDI-II increased from 27.0 to 30.8 (mean difference +3.8). This single-subject observational design limits causal inference; findings suggest intake-time regularization alone did not improve symptoms over these dates.

Submission Number: 188