Читать книгу Introduction to Abnormal Child and Adolescent Psychology - Robert Weis - Страница 129

There are two types of correlational designs that are especially relevant to researchers who study childhood disorders: (1) cross-sectional and (2) longitudinal (Kazdin, 2017).

In a cross-sectional study, researchers examine the association between variables at the same point in time. For example, Humphreys and colleagues (2013) assessed the relationship between children’s ADHD symptoms and mood. They found a significant, positive correlation between these variables: children with more ADHD symptoms also experienced more symptoms of depression. However, the researchers could not determine the direction of this relationship because the variables were assessed at the same point in time.

In a longitudinal study, researchers specify the direction of the relationship between variables by measuring them at different times. In a prospective longitudinal study, researchers measure a hypothesized predictor variable at Time 1 and measure its expected outcome at Time 2. For example, Humphreys and colleagues (2013) conducted a second, prospective longitudinal study examining children’s ADHD symptoms in early childhood and depressive symptoms in early adulthood. They found a significant, positive correlation between early attention problems and later depression. Because children’s ADHD and depressive symptoms were assessed at different points in time, the researchers concluded that children’s attention problems emerged before their depressive symptoms (Markon & Markon, 2018).

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Figure 3.2 ■ Correlations Do Not Imply Causality

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Note: (A) Children’s behavior problems can increase parenting stress; (B) parenting stress can increase behavior problems; or (C) other factors, such as divorce, can increase both behavior problems and parenting stress.

Prospective longitudinal studies are difficult to conduct because researchers must wait a long time to test their hypotheses and participants often drop out of studies before completion. Consequently, some researchers use other methods. In a retrospective longitudinal study, researchers recruit individuals with a known disorder and ask them (or their parents) to recall events in the past that might have predicted its emergence. For example, researchers might recruit a large sample of young adults with depression. Then, they might ask their parents to recall symptoms of ADHD that these adults showed as children. The chief limitation of retrospective longitudinal studies is that people may not accurately recall past events.

In a follow-back longitudinal study, researchers recruit individuals with a known disorder and examine their medical records, school reports, or other objective data for events in the past that might have predicted its emergence. For example, researchers might ask young adults with depression for permission to review their childhood medical records. The researchers could then determine if participants were ever diagnosed with ADHD or prescribed medication to treat attention problems when they were children. Follow-back studies do not rely on people’s memories of past events. However, obtaining high-quality records is often difficult (Wright & Markon, 2018).