An exploration of actigraphy in the context of ketamine and treatment‐resistant depression

Objectives This study explored the potential of non‐parametric and complexity analysis metrics to detect changes in activity post‐ketamine and their association with depressive symptomatology. Methods Individuals with treatment‐resistant depression (TRD: n = 27, 16F, 35.9 ± 10.8 years) and healthy volunteers (HVs: n = 9, 4F, 36.4 ± 9.59 years) had their activity monitored during an inpatient, double‐blind, crossover study where they received an infusion of ketamine or saline placebo. All participants were 18–65 years old, medication‐free, and had a MADRS score ≥20. Non‐parametric metrics averaged over each study day, metrics derived from complexity analysis, and traditionally calculated non‐parametric metrics averaged over two weeks were calculated from the actigraphy time series. A separate analysis was conducted for a subsample (n = 17) to assess the utility of these metrics in a hospital setting. Results In HVs, lower intradaily variability was observed within daily rest/activity patterns post‐ketamine versus post‐placebo (F = 5.16(1,15), p = 0.04). No other significant effects of drug or drug‐by‐time or correlations between depressive symptomatology and activity were detected. Conclusions Weak associations between non‐parametric variables and ketamine were found but were not consistent across actigraphy measures. Clinical Trial registration ClinicalTrials.gov, NCT00088699.