Background: This study explored the relationship between personality disorder (PD) and treatment response in a randomized, double-blind, clinical trial of osmotic release oral system (OROS) methylphenidate (MPH).
Methods: Forty-seven patients entered a crossover trial using the Wender-Reimherr Adult Attention Deficit Disorder Scale (WRAADDS) to assess outcome. A final personality diagnosis was made using staff consensus and information from the Wisconsin Personality Inventory IV (WISPI-IV) and the Structured Clinical Interview for DSM-IV Axis II Personality Disorders (SCID-II). Three post hoc categories were created: PD-negative (no PD; n = 26), PD-positive (patients with 1 PD; n = 11), and PD-plus (patients with 2 or more PDs; n = 10). Improvement in attention-deficit/hyperactivity disorder (ADHD) symptoms was assessed using a mixed-model analysis with treatment and personality categories as fixed variables. Average z scores on the WISPI-IV and items endorsed on SCID-II provided dimensional measures of PD severity.
Results: Different treatment effects were observed for the PD subgroups (P < .001). PD-negative patients improved 40% on OROS MPH vs 7% on placebo, and PD-positive patients improved 66% on OROS MPH vs 9% on placebo. In contrast, PD-plus patients improved 26% on OROS MPH vs 23% on placebo.
Conclusion: Most patients experienced significantly reduced ADHD symptoms on OROS MPH; however, patients with 2 or more PDs did not. The 2 alternate measures of PD supported this observation in this small exploratory study.