The challenges to demonstrating long-term effects of psychostimulant treatment for attention-deficit/hyperactivity disorder:

Questions about the long-term effects of psychostimulant medication are frequently raised in the public domain. There is a need to articulate the methodological challenges to addressing this question, both to assist in the interpretation of existing research and to inform future research. Two peer-reviewed studies and one published report have attempted to address the issue of long-term effects of psychostimulant medication. One is favourable, one found no benefit, and the third showed harm. All three studies struggled to deal with methodological challenges such as the variable time course of the disorder, variability in persistence and adherence with treatment, and self-selection for treatment continuation. Future research examining the long-term effects of psychostimulant treatment will of necessity be naturalistic, but must be able to control for treatment quality, treatment adherence, and natural variation in the course of attention-deficit/hyperactivity disorder. It would be helpful to distinguish between long-term effects of treatment and effects of long-term treatment.