We aimed to investigate which items of the Yale-Brown Obsessive-Compulsive Severity Scale best discriminate the reduction in total scores in obsessive-compulsive disorder patients after 4 and 12 weeks of pharmacological treatment. Data from 112 obsessive-compulsive disorder patients who received fluoxetine (⩽80 mg/day) for 12 weeks were included. Improvement indices were built for each Yale-Brown Obsessive-Compulsive Severity Scale item at two timeframes: from baseline to week 4 and from baseline to week 12. Indices for each item were correlated with the total scores for obsessions and compulsions and then ranked by correlation coefficient. A correlation coefficient ⩾0.7 was used to identify items that contributed significantly to reducing obsessive-compulsive disorder severity. At week 4, the distress items reached the threshold of 0.7 for improvement on the obsession and compulsion subscales although, contrary to our expectations, there was greater improvement in the control items than in the distress items. At week 12, there was greater improvement in the time, interference, and control items than in the distress items. The use of fluoxetine led first to reductions in distress and increases in control over symptoms before affecting the time spent on, and interference from, obsessions and compulsions. Resistance did not correlate with overall improvement. Understanding the pathway of improvement with pharmacological treatment in obsessive-compulsive disorder may provide clues about how to optimize the effects of medication.
