A longitudinal study of neurobiological mechanisms in boys with attention-deficit hyperactivity disorder: Preliminary findings

Background: The stability, and developmental variation of several neurobiological measures in boys with attention-deficit hyperactivity disorder (ADHD) were examined. Methods: The prolactin (PRL) response to fenfluramine (FEN) challenge was used to assess central serotonergic (5-HT) functioning in 10 8-11-year-old boys with ADHD. In addition, platelet 5-HT, as well as plasma levels of the catecholamine metabolites 3-methoxy-4- hydroxyphenylglycol (MHPG) and homovanillic acid were ascertained. These neurobiological variables were reassessed in the same children 2-3 years later using the identical procedures. Results: The PRL response to FEN challenge was the only measure found to be stable across the evaluations (r = .58), although the magnitude of the response decreased significantly with age. Plasma MHPG level significantly increased with age. Conclusions: Central 5-HT function, as measured by the PRL response to FEN, may represent a stable trait. The importance of considering developmental factors when interpreting neurobiological data is discussed.