Neurochemical Correlates of Attention Deficit Disorder

Neurobiology of ADHD

“…The later study also found that baseline CSF HVA concentration was a predictor of stimulant drug response, with higher HVA levels being associated with better drug response (Castellanos et al, 1996). These results are consistent with findings that CSF HVA levels decrease after treatment with stimulants (Castellanos, 1997;Raskin et al, 1984;Weizman et al, 1990), and also decrease with age (Castellanos, 1997). These findings and the assumption based on animal studies that the majority of CSF HVA originates in the striatum, led Castellanos (1997) to conclude that the motor hyperactivity in ADHD may be associated with increased HVA concentrations in the caudate, as would be found in younger children.…”

“…As with dopamine metabolite levels, there are conflicting findings for MHPG levels, with some studies finding reduced urinary MHPG in children with ADHD (Shekim et al, 1977(Shekim et al, , 1979(Shekim et al, , 1983(Shekim et al, , 1987, others finding increased levels (Khan & Dekirmenjian, 1981;Oades et al, 1998), and others finding no difference relative to controls (Rapoport et al, 1978). Some of the discrepancies among findings may be explained by subjects' prior use of stimulants, as urinary MHPG concentrations have been found to decrease after treatment with dexamphetamine, but not after treatment with methylphenidate (Raskin et al, 1984;Weizman et al, 1990). MHPG concentrations in plasma and in CSF have also been measured in just a few studies.…”

“…As direct measurement of catecholamine concentrations in the brain is not possible, evidence for differences in ADHD has been sought from measurements of catecholamine metabolite concentrations in cerebrospinal fluid (CSF), blood and urine. The results of these studies are inconsistent (Cantwell, 1996;Mason, 1984;Pliszka et al, 1996;Raskin et al, 1984;Weizman et al, 1990), thus the precise nature of catecholamine anomalies in ADHD remains unknown and several different theories have been suggested.…”

“…The best measure of CNS dopamine levels is thought to be the concentration of homovanillic acid (HVA) in CSF (Castellanos, 1997;Raskin et al, 1984). Some early studies found reduced HVA levels in CSF or urine in children with ADHD compared with controls (Shaywitz et al, 1977), while other studies found no group differences (Shekim et al, 1977(Shekim et al, , 1979Shetty & Chase, 1976).…”

The EEG Consistency Index as a Psycho-Physiological Marker of ADHD and Methylphenidate Response: Replication of Results

“…Determining a biological measure that could aid in the diagnosis of ADHD would help to refine diagnostic criteria and may provide more specific diagnostic tests for ADHD and other disorders of attention and self-regulation. Although research supports a neurological basis for ADHD (Hynd et al, 1991;Castellanos, 1997;Berquin et al, 1998;Mostofsky, Reiss, Lockhart, & Denckla, 1998;Raskin, Shaywitz, Shaywitz, Anderson, & Cohen, 1984: Crawford & Barbasz, 1996Heilman, Voeller, & Nadeau, 1991;Zametkin et al, 1990;Castellanos et al, 2001;Castellanos et al, 2002) there are few definitive large studies examining EEG as a quantifiable physiological marker of ADHD.…”