functioning or symptoms outside of a normative range. For example, think about when you were in high school: it might be considered “normal” to feel sad some days, get upset, and want to sleep in late. However, if someone was staying in bed for two weeks at a time to sleep, feeling sad or depressed most of the time, and not having fun with activities they used to enjoy, that could indicate “abnormal” functioning, such as signs of a depressive disorder. Developmental psychopathology allows us to compare and measure psychopathology across a continuum of normal to abnormal.
Other examples of the interplay between normal and abnormal may include individuals who fail to meet developmental expectations due to psychopathology. Across the lifespan, there are established developmental milestones, or indicators for how an individual has adapted and is functioning in their environmental context. At different stages of development, there are expected milestones and behaviors that are considered normal or abnormal for that stage.
Think about a toddler: they are learning to feed themselves, walk independently, regulate their own emotions or needs, and form attachments to their caregiver. If a toddler were to be separated from their caregiver, it would be considered normal for them to cry and become upset. However, if an eight‐year‐old demonstrates similar behavior, such as throwing a tantrum, screaming, and crying every time they are separated from their parent, this would be considered abnormal, and potentially indicative of psychopathology. Thus, understanding variation in normal/abnormal behaviors across development may improve understanding of those at risk for mental health problems.
Studying Developmental Continuities and Discontinuities of Traits, Behaviors, Emotions, And Disorders
The next principle is that developmental psychopathology models examine developmental continuities and discontinuities of traits, behaviors, emotions, and disorders. Homotypic continuity is defined as stability in the same or similar behavioral responses over time; that is, the same disorder predicts itself over time (e.g., earlier depression predicting later depression). Heterotypic continuity is defined as stability of an underlying construct that is exhibited differentially across development (Sroufe & Rutter, 1984); that is, different disorders predict one another over time (e.g., anxiety predicting later depression).
Consider externalizing or antisocial behaviors, which have established stability across the lifespan. What does this mean? Rank order stays the same across time, so individuals that are more aggressive early in life are also more aggressive than others later in life. However, the specific externalizing behaviors exhibited may look different over time. For example, during early childhood, children may show extreme temper tantrums but are not likely to display the same behavior during adolescence. As shown in Figure 2.1, the nature of externalizing or antisocial behavior changes as children get older and become adults. This demonstrates heterotypic continuity, as the form or manifestation of the trait changes with development.
FIGURE 2.1 Example of Heterotypic Continuity. The Nature of Externalizing or Antisocial Behavior Changes as Children Get Older and Become Adults
Another important concept in developmental psychopathology is pathways, or how individuals change and adapt over time and reach different outcomes or pathologies. Equifinality refers to the idea that many different pathways or early experiences may lead to the same outcome or condition (see Figure 2.2b).
For example, conduct disorder could occur due to early child abuse, heritable tendency toward externalizing behaviors, familial factors such as harsh parenting interactions or attachment disruption, environmental factors such as prenatal risk factors, or exposure to trauma. It is more likely that a combination or interaction of these multiple vulnerability and risk factors contributes to the development of psychopathology. Correspondingly, multifinality refers to how similar early experiences or risk factors can lead to different outcomes (Cicchetti & Rogosch, 1996) (See Figure 2.2a). For example, early maltreatment may lead to the development of psychopathology or not, depending on a variety of other factors.
Individuals or subgroups may have different pathways or trajectories across development that affect these patterns of continuity. In our previous example of children who start off highly aggressive in preschool, some children may “return to normal” behavior by adolescence, whereas others may maintain high rates of externalizing behaviors. Additionally, other groups of children do not display externalizing problems in early childhood, but their problems emerge in adolescence (Moffitt, 2003). This variety demonstrates the different pathways, patterns, and subgroups of individuals and how they change over time, which is a key principle of developmental psychopathology. Developmental psychopathology aims to understand these behaviors and problems over time and determine how we can predict these different trajectories.
Evaluating Evidence Across Multiple Levels of Analyses To Include the Biological, Individual, Family, Social, and Cultural Levels
The next principle of developmental psychopathology is that research should examine multiple levels of analyses to include biological, individual, familial, social, and cultural levels. Developmental psychopathologists have learned that to answer their overarching questions about processes of psychopathology and development, they need to incorporate scientists from different fields and use different levels and methods of analysis. Key models that have influenced the multilevel principle include Bronfenbrenner’s (1979) ecological model, Sameroff’s (1989) model of gene and environment interactions, and Gottlieb, Wahlsten, and Lickliter’s (2007) model of four levels (environment, behavior, neural activity, genetics) and how these levels influence one another. The takeaway from these different models is that we should study processes and systems at multiple levels and how they interact across levels to better understand psychopathology and the risk for disorders.
FIGURE 2.2 A. Multifinality: Similar Early Experiences Lead to Different Outcomes. B. Equifinality: Different Early Experiences Lead to a Similar Outcome.
Reproduced with permission of Getty Images. Sources: (a) SW Productions/Photodisc/Getty Images. (b) Yellowsarah/iStock/Getty Images.
FIGURE 2.3 Multiple Levels of Analyses
Figure 2.3 shows commonly studied levels of analyses in developmental psychopathology studies. As discussed above, pathways to psychopathology can vary, so it is important to consider contextual factors. There are factors or levels that we can study across individuals (e.g., high and low socioeconomic status) or within individuals (e.g., temperament, genetics, brain activity). Developmental psychopathology brings together these micro and macro levels to study how the individual functions in their larger context.
Incorporating Distinct Perspectives Across Clinical, Developmental Psychology, Child/Adolescent Psychiatry, Genetics, Neurology, Public Health, and Philosophy of Science Into A Multidisciplinary Effort
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