In assessing effectiveness of treatments for ADD syndrome, it is important to ask: What is the desired outcome? Some studies answer this question by analyzing how stimulant medications affect a patient's performance not on combined DSM-IV symptoms of ADHD, but on specific tasks orchestrated by executive functions. Seven of these studies are briefly described here.
Often persons with ADD work too quickly and don't recognize when they need to slow down to do a good job. Deborah Krusch and others (1996) studied the accuracy and processing speed of children with ADD. On the medication the children showed improvement on several executive functions: focus, self-monitoring of action, and processing speed.
Virginia Douglas (1999) demonstrated an even broader effect of meth-ylphenidate (MPH) on self-regulation in children with ADHD. When provided MPH, boys with ADHD appropriately speeded up for more automatic, faster-paced tasks and slowed down as needed for complicated tasks that required more concentration and effort.
Persons with ADHD often complain of being too easily distracted. Caryn Carlson and colleagues (1991) found that while on medication boys with ADHD were better able to ignore distractions and to sustain focus and maintain speed and accuracy on their primary task.
Some parents and teachers believe that tangible rewards will motivate children with ADHD to work better on tasks that do not interest them.
Mary Solanto and others (1997) studied whether medicine or rewards would work better to get children with ADHD to keep working on a long, boring computer task. Their results showed that both the money-earning and the medication improved accuracy overall, but the MPH was significantly more potent; MPH also improved the ability of the children to sustain their attention and effort on the task, while the monetary rewards did not.
John Chelonis (2002) tested whether MPH significantly improves working memory in children with ADHD. In a series of trials, children with ADHD were significantly more accurate and efficient in remembering shapes correctly when on the MPH than when off it; on medication, their performance became as efficient as that of normal children of the same age range. The medication normalized their impaired working memory.
Individuals with ADHD are often too quick to give up when frustrated. Richard Milich and colleagues (1991) asked boys with ADHD to solve a series of puzzles, some of which were unsolvable. They tested whether while taking MPH these boys, after experiencing frustration from failing to solve some unsolvable puzzles, would keep trying to solve other puzzles longer than they did when taking a placebo. They found that the boys did significantly better on medication than on placebo following exposure to unsolvable puzzles ... in fact, the boys' best performance occurred in the medication/insolvable condition. . . . ADHD boys on placebo tend to get discouraged and exert less effort after failure experiences. ... In contrast, on medication they adopt a more adaptive strategy of trying even harder after experiencing problems they could not solve. (p. 530)
Often children and adults with ADD syndrome are too impulsive; that is, not able to hesitate long enough to make a sensible response. AnneClaude Bedard and others (2003) used a computer task to test children with ADHD on their ability to hold back a response until a signal was given. On medication, the children stopped themselves more quickly from making incorrect responses and were quicker and more consistent in making accurate responses. The researchers suggested that
MPH may influence global cognitive processes, such as atten-tional capacity or working memory, that are deficient in children with ADHD and result in improvements in aspects of response inhibition, as well as response execution. (p. 325)
Taken together, these various studies demonstrate that stimulant medications improve a variety of functions impaired in ADD syndrome. These include sustaining alertness, focus, motivation, and effort for tasks that are not intrinsically interesting; shifting attention as needed; utilizing working memory; adjusting processing speed to the demands of the task; sustaining processing speed for efficient performance; managing emotions to persist despite frustration and failure; and monitoring and self-regulating actions. These laboratory measures stand with a large body of research over the past half-century that powerfully demonstrates the effectiveness of stimulant medications for alleviating a wide variety of impairments associated with ADD syndrome.
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