Moderators and Mediators of Symptoms and Quality of Life Outcomes in an Open-Label Study of Adults Treated for Attention-Deficit/Hyperactivity Disorder

Objective: The Quality of Life, Effectiveness, Safety, and Tolerability (QU.E.S.T.) study was designed to evaluate effectiveness of long-acting amphetamines in adults with attention-deficit/hyperactivity disorder (ADHD) in community practice settings. This article reports moderators and mediators of symptoms and quality of life outcomes.

Method: This was an open-label study of 725 adults with DSM-IV-diagnosed ADHD, treated with mixed amphetamine salts extended release and followed for up to 8 months. Multiple regressions were used to determine if patient moderators impact response in ADHD symptoms and how ADHD symptoms and medication satisfaction mediate quality of life. The study was conducted from December 2003 to December 2004.

Results: Amphetamine treatment of ADHD resulted in a robust and enduring symptom response. Patient characteristics such as age, female gender, severity of illness, and treatment-naive status moderate improved symptom outcome. Symptom change and satisfaction with medication independently mediate change in mental but not physical quality of life outcomes. There is no time lag between changes in symptoms and improved quality of life. Attention is a stronger mediator of ADHD-specific quality of life outcomes than disruptive behavior.

Conclusions: If symptoms and quality of life improve simultaneously, improvement in quality of life can be understood as more than just a downstream, secondary effect of symptom remission. Satisfaction with medication is a direct measure of the complex interplay of symptom change, tolerability, and patient perception of treatment that predicts self-report of quality of life benefits. Although the disruptive symptoms of ADHD are more obvious, adults self-report that attention has greater impact.

J Clin Psychiatry

Submitted: March 14, 2008; accepted January 2, 2009.

Online ahead of print: February 23, 2010.

Corresponding author: Christopher Gibbins, PhD, Box 178, Children’s and Women’s Health Centre, 4500 Oak St, Vancouver, BC V6H 3N1, Canada ([email protected]).