Kate Humphreys
ADHD In children and adults – Symptoms and tests
Children with attention deficit hyperactivity disorder (ADHD, formerly known also as ADD) are classically seen as the kids in class who have trouble staying in their seats and paying attention during long lessons. Underlying these problematic behaviors is a confluence of factors, with evidence pointing to genetics, neural function, and environmental factors (including parenting and lead exposure) that can all affect ADHD behavior. Many children diagnosed with ADHD seem to simply “grow out” of their symptoms. They may learn particularly effective strategies for managing inattention and disorganization (I myself am a notorious list maker), or learn to control some of the fidgeting and restlessness or channel that energy into sports or other activities.
Scientists who want to find the source of inattention, hyperactivity, and impulsivity have been trying to use measures that more directly approximate brain activity. The idea is that neurocognitive tests, presumably linked to specific functions in the brain, may help to gain insight into the causes of ADHD. These tests vary widely, and measure things like the response speed, planning, memory capacity, and the extent to which someone chooses a smaller reward now or a larger rewards later.
ADHD Research – Knowing what’s important to know
One recent neurocognitive study, which I coauthored, asked children with and without ADHD to pay attention to a series of word lists with 12 words each and then tell an examiner as many words they could remember. This type of task requires individuals to try to hold as many “objects” in place at one time, which can be very difficult. Most adults can usually hold between 5 and 9 items in their working memory, a fact that is closely tied to the the number of digits in phone numbers around the world.
So asking people how many words they can remember of the 12 words could give a pretty good sense of their general short term memory capacity. In every day life, the size of our memory storage may not seem essential. What might matter more is which of the many things you actually do recall. For example, if you were going to the grocery store to get supplies for making cookies, it is probably more important to remember ingredients like flour and sugar than something extraneous, like sprinkles. Of course it would be great to remember everything, but certainly some things have more utility to certain tasks.
Our group of researchers in this recent study added a feature to the task – Each word on the wordlist was paired with a point value between 1 and 12. For example, bird was paired with 2 points, shoe was paired with 6 points, and clock was paired with 11. You would do best if you could recall all of the words, because that would result in the greatest number of points. However, if you realize that you may not be able to recall all 12 words, it makes sense to try harder to remember the words worth the highest value, although this point was not made explicitly to the participants. So in this case, you should try the hardest to remember clock, followed by shoe, and then bird. Those individuals who are more selective in the words they recall focus strategically on high-value words. Given a memory that can only store a certain number of words, recalling words worth more points is the most effective strategy. Given that memory capacity (amount of words remembered) and memory efficiency (value of word remembered) are not the same, perhaps figuring out if some individuals have poorer performance in one area versus another can give insight into the neural factors related to behaviors relevant to daily life.
The results: Children with and without ADHD were able to remember the same number of words from the lists – on average each group recalled just over 3 words per list. However, when it came to the memory efficiency, or choosing to remember high value words over lower value words, there was an important difference. Children with the Combined Type of ADHD (those with symptoms above the cutoff for inattention and hyperactivity and impulsivity) had significantly worse selective memory than children without ADHD. Typically developing children were more likely to recall the words paired with 10, 11, and 12 – seeing quickly that these words are very important to remember. However, children showing many ADHD symptoms did not have as strong as a response. For some reason, their “high alert” was not activated for high value words the same way it was for the non-ADHD kids, because they were less likely to recall high value words. Using a selectivity index (ranging from -1 to +1), in which higher scores indicate individuals selecting higher value words, kids without ADHD had an average of .27, while children with ADHD-Combined Type had an average score of .14. This translates into children without ADHD being roughly twice a selective!
Inability to control attention may result in less efficient memory function
This has interesting implications for thinking about ADHD. We know that these individuals are just as capable when it comes to remembering information, but it seems that what they end up remembering could be an issue. The brain areas associated with planning, memory, and decision-making are also implicated in a number of other psychological disorders. Decisions about risk-taking, substance use, and other problematic behaviors may be impaired in children with ADHD compared to their non-ADHD counterparts. Another recent study looking at the long term outcomes of children with ADHD found that as adolescents and adults, they are more likely to try smoking and marijuana, and more likely to develop substance abuse or dependence on nicotine, marijuana, alcohol, cocaine, and other drugs.
It’s important to note that there are certainly many healthy and successful adults who had ADHD as children and still have many symptoms that they manage successfully. Still, this group merits further attention for prevention and intervention efforts in the domain of addiction.
References:
Castel, A. D., Lee, S. S., Humphreys, K. L., & Moore, A. N. (2011). Memory capacity, selective control, and value-directed remembering in children with and without attention-deficit/hyperactivity disorder (ADHD). Neuropsychology, 25, 15-24.
Lee, S. S., Humphreys, K. L., Flory, K., Liu, R., & Glass, K. (2011). Prospective association of childhood attention-deficit/hyperactivity disorder (ADHD) and substance use and abuse/dependence: A meta-analytic review. Clinical Psychology Review, 31, 328-341.