5-Hydroxytryptophan as adjuvant therapy in treatment of moderate to severe obsessive-compulsive disorder: a double-blind randomized trial with placebo control

Int Clin Psychopharmacol. 2020 Sep;35(5):254-262. doi: 10.1097/YIC.0000000000000321.


On the basis of numerous previous studies, the serotonergic system plays a role in the pathogenesis of obsessive-compulsive disorder (OCD) and effective agents in this pathway, such as 5-hydroxytryptophan, can potentially contribute to treatment of patients with this disorder. Evaluating the efficacy of 5-hydroxytryptophan in treating OCD was the aim of the present randomized, double-blind, placebo-controlled 12-week trial. In a 12-week, randomized double-blind study, 60 patients with a Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition diagnosis of moderate to severe OCD and a Yale-Brown Obsessive Compulsive Scale (Y-BOCS) score of >21 were randomly assigned to receive either fluoxetine plus placebo or fluoxetine plus 5-hydroxytryptophan (100 mg twice daily). All patients, regardless of their treatment group, received fluoxetine at 20 mg/day for the initial 4 weeks of the study followed by 60 mg/day of fluoxetine for the rest of the trial course. Symptoms were assessed using the Y-BOCS at baseline and weeks 4, 8 and 12. General linear model repeated measure showed significant effects for time × treatment interaction on total Y-BOCS (F = 12.07, df = 2.29, P-value <0.001), obsession (F = 8.25, df = 1.91, P-value = 0.001) and compulsion subscale scores (F = 6.64, df = 2.01, P-value = 0.002). 5-Hydroxytryptophan augmentation therapy demonstrated higher partial and complete treatment response rate (P = 0.032 and P = 0.001, respectively) according to the Y-BOCS total scores. The results of this study confirm that 5-hydroxytryptophan may be effective as an augmentative agent in treatment of moderate-to-severe OCD.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 5-Hydroxytryptophan / therapeutic use*
  • Adult
  • Double-Blind Method
  • Drug Therapy, Combination
  • Female
  • Fluvoxamine / therapeutic use
  • Humans
  • Male
  • Obsessive-Compulsive Disorder / drug therapy*
  • Treatment Outcome
  • Young Adult


  • 5-Hydroxytryptophan
  • Fluvoxamine