Image courtesy of the National Library of Medicine

      Bradley had stumbled upon the use of stimulants as an effective way to treat ADHD. Today, medications like amphetamine (Adderall) and methylphenidate (Ritalin) are the most effective treatments for this disorder (Faraone & Buitelaar, 2010).

      Many of the boys also showed problems with attention and concentration:

      The children cannot concentrate on difficult tasks. They also show no perseverance in their activities. They often disturb class, have difficulty playing harmoniously with others, and are generally unpopular with peers.

      Kramer and Pollnow’s descriptions provide the basis for the disorder we now call ADHD. The two broad clusters of symptoms that they identified, hyperactivity and inattention, are still used today to diagnose children with this disorder. Another clinician, Charles Bradley, used the case study approach to describe a possible treatment for these children as described in the From Science to Practice section.

      Case studies have several limitations. Most importantly, the results of a case study may not generalize to a wider population. Although stimulant medication worked for several of Bradley’s patients, it wasn’t until the 1950s that Ritalin was shown to help most children with attention problems. Case studies are also prone to the biases of the researcher who conducts them. Bradley may have observed improvements in his patients simply because he expected the medication to help them. Finally, because each child is unique, the results of case studies are difficult to replicate. We need to conduct systematic studies, with larger samples of children, before we can be sure that the phenomena described in case studies are accurate and applicable to a wide range of children.

      Surveys

      Surveys are often used to describe large groups of children. Whereas case studies focus on the idiographic assessment of an individual child, surveys focus on nomothetic assessment—that is, information about how groups of children typically think, feel, or act. For example, psychologists might conduct surveys to determine the percentage of school-age children with ADHD, the age at which children first develop symptoms, or parents’ attitudes toward medication to treat the disorder.

      The results of a survey depend on how participants are selected. Researchers cannot survey everyone in the entire population. Instead, researchers must select a sample of participants for their study. Ideally, researchers will use random selection, that is, they will select participants so that each person in a given population has an equal chance of being included in the study. If participants are randomly selected, then the information they provide should reflect the characteristics of the general population (Hsu, 2017).

      For example, researchers at the Centers for Disease Control wanted to determine the prevalence of ADHD among children in the United States. They randomly selected a large sample of children using records from the federal census. Then, they asked the parents of each randomly selected child to report if their child had ever been diagnosed with ADHD. The researchers found that 9.1% of children had been diagnosed with ADHD, reflecting about 6.1 million children across the country. Because the researchers randomly selected participants for the survey, they can be reasonably confident that the data they gathered reflect the prevalence of ADHD in the general population (Danielson et al., 2018).

      Most surveys are quantitative, that is, they collect numerical data or ratings provided by children, parents, or other informants. For example, a researcher might ask a parent if her child has ever been diagnosed with ADHD or ask a teacher to report the severity of his student’s attention problems on a scale ranging from 1 (low) to 7 (high). Surveys can also be qualitative, that is, they may ask respondents to provide verbal descriptions of children’s behavior. For example, survey questions might ask a parent to list three strengths about her child or ask a teacher to describe the child’s typical behavior during class.

      Neuroimaging

      Neuroimaging methods are also used to describe the brain structure and functioning of children with mental health problems. Beginning in the 1970s, clinicians and researchers used computed tomography (CT) to obtain more detailed images of the brain. In CT scanning, multiple images are taken using a movable X-ray device. A computer integrates these images to provide a clear picture of the brain. Unfortunately, CT scanning exposes patients to radiation. Consequently, it must be used sparingly with children (Roberts, 2020).

      In the 1980s, a new tool was developed: magnetic resonance imaging (MRI). MRI technology is based on the fact that when body tissues are placed in a strong magnetic field and exposed to a brief pulse of radiofrequency energy, cells from the tissue emit a brief signal, called a resonance. Different types of tissue give off slightly different signals. In the brain, neurons (i.e., gray matter), myelin (i.e., white matter), and cerebrospinal fluid give different signals. A computer can use these different signals to generate a digital image of the brain. MRI machines generate two-dimensional images of brain tissue that can be integrated by the computer (i.e., “stacked” on top of one another) to create a three-dimensional picture (Picon, Volpe, Sterzer, & Heinz, 2016).

      MRI has a number of advantages over CT and most other imaging techniques. First, MRI does not subject individuals to radiation; it is believed to be safe and has even been used to obtain images of the brains of developing fetuses. Second, because it is safe, MRI can be used with healthy children and administered repeatedly over time. Consequently, MRI technology allows us to study the same children’s brains across development. Third, MRI yields clearer and more precise pictures of the brain than older neuroimaging methods (Giedd & Denker, 2015).

      MRI can allow us to detect structural abnormalities in the brains of youths with mental disorders. In a typical MRI study, researchers scan the brains of youths with and without a specific disorder. For example, Castellanos and colleagues (2002) scanned the brains of children with and without ADHD. The researchers compared the volumes of the frontal cortex of children in the two groups. They found that children with ADHD showed an average 4% reduction in volume of the frontal cortex compared to children without ADHD. These results are important because underactivity in portions of the frontal cortex is believed to account for some ADHD symptoms.

      Functional magnetic resonance imaging (fMRI) is used to measure brain activity. The fMRI machine measures changes in oxygenated hemoglobin concentrations in the brain. When the individual engages in mental activity, oxygenated hemoglobin concentrations increase in brain regions that become active. Consequently, fMRI yields a picture of the individual’s brain showing regions most active during certain mental activities (Sadock & Sadock, 2015).

      To perform fMRI, researchers typically obtain an image of the individual’s brain, using traditional MRI. Then, researchers ask the individual to perform a series of mental activities while they collect fMRI data. For example, researchers might ask adolescents with autism to describe the emotional expression on pictures of people’s faces or ask children with learning disabilities to read or solve math problems. These fMRI images are then superimposed over the traditional MRI to show brain regions that are most active during the mental tasks.

      Tamm, Menon, and Reiss (2006) used fMRI to determine which brain regions might be responsible for the deficits in attention shown by youths with ADHD. They asked adolescents with and without ADHD to perform a test of attention while they collected fMRI data. Specifically, youths were presented with a series of either circles or triangles. They were asked to press one button when they saw a circle and a different button when they saw a triangle. As expected, youths with ADHD made significantly more errors than youths without ADHD. Furthermore, youths with ADHD showed significantly less activity in certain brain areas compared to their healthy peers. The researchers concluded that these brain regions may play a role in people’s ability to direct and regulate attention.

      Sometimes, children show