Impact of Comorbidity on Treatment - Attention-deficit and Disruptive Behavior Disorders

Impact of Comorbidity on Treatment

Studies of stimulant treatment have shown that ADHD chil-dren with and without aggression respond equally well to MPH treatment in terms of ADHD symptoms. Research examining whether aggression in ADHD children can be treated with psy-chostimulants has mainly yielded positive findings. Finally, one study found that some covert, nonaggressive symptoms (e.g., stealing) were also decreased in ADHD children (independent of comorbidity) following treatment with MPH (Hinshaw et al., 1992). Treatment of comorbid ADHD and CD/ODD in the MTA study was superior when medication was used, although the best outcome was seen with combined treatment (Jensen et al., 2001).

While it is now clear that stimulant treatment can improve performance on a wide array of cognitive measures, treatment of comorbid learning disabilities requires direct, nonpharmaco-logical, academic interventions. There has been some concern regarding the possible dissociation of cognitive and behavioral effects of stimulant medication. One landmark study found that optimal cognitive performance was achieved at low doses (i.e., 0.3 mg/kg) while optimal behavioral function was achieved at high doses (i.e., 1.0 mg/kg), with an accompanying decline in cognitive function at the higher dose (Sprague and Sleator, 1977). However, other investigators have reported a linear rather than a curvilinear dose–response curve for both behavioral and cognitive functions and have therefore not supported the previ-ously hypothesized “cognitive toxicity”.

In contrast to studies in children with ADHD who are ag-gressive, studies of stimulant response in ADHD children with comorbid anxiety have produced somewhat inconsistent find-ings.Recent studies have found that medication is equally ef-fective in comorbid ADHD and anxiety disorders. Other stud-ies have found that children with ADHD and anxiety respond as well as those without comorbid anxiety to the antidepressant DMI (Biederman et al., 1993).