PS94. Title: Digit span-forward as a predictor of fluoxetine outcome for patients with major depressive disorder

Abstract

Objective: The objective of this paper was to determine whether baseline subtests and intelligence quotient (IQ) using Wechsler Adult Intelligence Scale (WAIS-III) were associated with treatment outcomes for patients with major depressive disorder (MDD) receiving 6-week fluoxetine treatment.

Methods: A total of 131 acutely ill MDD inpatients were enrolled to receive 20mg of fluoxetine daily for 6 weeks. WAIS-III with 8 subtests (picture completion, digit symbol, similarities, block design, arithmetic, digit span-forward, digit span-backward, and information) were rated by licensed clinical psychologist at baseline. Symptom severity and functional impairment were assessed at baseline, and again at weeks 1, 2, 3, 4, and 6 using the 17-item Hamilton Depression Rating Scale (HAMD-17) and Modified Work and Social Adjustment Scale (MWSAS) respectively. The generalized estimating equations method was used to analyze the influence of IQ scores and 8 subtest raw scores on the HAMD-17 and MWSAS over time after adjusting for sex, age, age at onset of illness, numbers of previous episode, and baseline severity (baseline HAMD-17 or MWSAS), respectively.

Results: Of the 131 participants, 104 (79.4%) who completed baseline measurements using WAIS-III and had at least one post-baseline assessment were included in the analysis. Subjects had low verbal IQ (VIQ) scores (88.8±13.7), performance IQ (PIQ) scores (83.7±14.7), and full scaled IQ (FSIQ) scores (86.4±12.9) than general population norms. PIQ scores were lower than VIQ scores. Patients experiencing less digit span-forward scores were more likely to have poor treatment outcomes regardless of symptom severity measured by HAMD-17 or functioning measured by MWSAS.

Conclusions: Discrepancy existing between VIQ and PIQ may be attributed to psychomotor retardation, a general slowing of mental processes recognized as a depressive symptom. MDD patients with lower scores of digital forwards were clinically useful in predicting poor outcomes after acute fluoxetine treatment.