with a disorder. Incidence refers to the percentage of new cases of a disorder in a discrete period of time.
Between 13% and 15% of youths experience a psychological disorder each year; 20% of youths experience a disorder before reaching adulthood. The most common disorders in children are ADHD and anxiety disorders.
Approximately 40% of youths with one disorder have another (comorbid) disorder.
What Factors Influence the Prevalence of Childhood Disorders?
Age
The prevalence of mental disorders varies with age. On average, adolescents are more likely than younger children to experience mental health problems. The best data that we have regarding the prevalence of mental health problems in adolescents comes from the results of the National Comorbidity Survey Replication–Adolescent Supplement (Kessler et al., 2012a). The researchers who conducted this study interviewed a nationally representative sample of more than 10,000 adolescents ages 13 to 17. They also administered rating scales to parents to gather additional data on adolescents’ functioning. Results showed that 23.4% of adolescents reported a mental health problem in the past month and 40.3% reported a mental health problem in the previous year. Although most of the problems experienced by adolescents were mild to moderate in severity, the overall prevalence of problems was much higher than in previous studies involving younger children (Kessler et al., 2012b).
The National Comorbidity Survey study also allows us to compare the prevalence of specific disorders across childhood and adolescence (Figure 1.2). Certain disorders are more common among younger children: autism, separation anxiety, and ADHD. However, the prevalence of most disorders increases with age. For example, adolescents are much more likely to experience problems with social phobia, depression, bipolar disorders, and eating disorders than prepubescent children. Problems with alcohol and other drug use also typically emerge in adolescence and are relatively rare among prepubescent children (Merikangas & He, 2014).
Figure 1.2 ■ The Prevalence of Childhood Disorders Varies by Age
Note: In general, adolescents are more likely to experience disorders than younger children. However, some disorders, like autism and separation anxiety disorder, are more common among younger children (Kessler et al., 2012a; Perou et al., 2016).
Gender
The prevalence of psychological disorders also varies across gender. In early childhood, many disorders are more typically seen in boys. For example, boys are 4 times more likely than girls to be diagnosed with autism spectrum disorder and 3 times more likely than girls to be diagnosed with ADHD. Boys are also more likely than girls to show disruptive behavior problems, such as oppositional defiant disorder. The prevalence of other disorders is approximately equal in young boys and girls (Perou et al., 2016).
By adolescence, however, girls are more likely than boys to experience mental health problems (Kessler et al., 2012a). Adolescent boys continue to be at greater risk than adolescent girls for conduct problems and physical aggression. Similarly, adolescent boys are slightly more likely than adolescent girls to develop problems with alcohol and other drugs. However, adolescent girls are 2 to 3 times more likely than adolescent boys to experience problems with depression or anxiety. Furthermore, adolescent girls are 5 to 10 times more likely than adolescent boys to be diagnosed with an eating disorder.
Psychologists have struggled to explain why girls show a dramatic increase in mental health problems during adolescence. Researchers have suggested many causes ranging from biological changes during puberty to unreasonable social–cultural expectations placed on females throughout the lifespan. Recently, however, researchers have identified two particularly important factors: stressful life events and the way girls think about those events.
In one study, researchers followed a large sample of adolescents from late childhood through middle adolescence (J. L. Hamilton, Stange, Abramson, & Alloy, 2015). Most youths reported increased stress during this time period; however, girls were particularly sensitive to interpersonal stressors—that is, stressful events that involved important people or relationships in their lives. For example, girls were especially likely to report difficulties with parents, peers, or romantic partners during their tween and teen years.
Perhaps more importantly, the way girls thought about these interpersonal stressors influenced their mood. For example, adolescents who believed they were responsible for these interpersonal problems (e.g., “It’s my fault my mom is angry with me”) were more likely to experience depression than adolescents who did not blame themselves (e.g., “My mom is just grouchy after working all day”). Similarly, adolescents who tended to overthink these events (e.g., “I wonder why my friends are mad at me? Was it something I said?”) were also more likely to experience problems with depression than girls who did not dwell on these events. These findings suggest that girls’ thoughts about interpersonal problems can greatly determine their well-being (From Science to Practice).
From Science to Practice: Interpersonal Stress and Gender
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Imagine that you are a middle school student. Some classmates are talking in the hallway. When you say “hi,” they ignore you. Why? Did you do something wrong? Did you say something stupid? Did you wear the wrong clothes to school that day?
Researchers found that adolescent girls are especially sensitive to interpersonal situations like these—much more than adolescent boys. When girls interpret these situations negatively (e.g., “They’re mad at me”), blame themselves (e.g., “I must have said something wrong”), and ruminate or think about the situation over and over, they can become depressed. In fact, adolescent girls are twice as likely as boys to develop depression.
Cognitive therapy is based on the premise that if adolescents can change the way they think about situations like these, they will feel better. A cognitive therapist would likely ask her client to look for alternative explanations for her classmates’ behavior. Is it possible that your classmates didn’t hear you say “hi” or they were busy doing something else? Generating alternative explanations for events like these can improve adolescents’ mood.
Note: Based on J. L. Hamilton and colleagues (2015).
Socioeconomic Status
Socioeconomic status (SES) is a variable that reflects three aspects of a child’s environment: (1) parents’ levels of education, (2) parents’ employment, and (3) family income. As you might expect, these three variables are correlated; parents with greater educational attainment tend to work more complex, higher-paying jobs. Overall, children from lower-SES families are at greater risk for developing mental disorders than children from middle- or high-SES families (Kessler et al., 2012a).
There are at least two explanations for the association between SES and risk for psychological disorders. First, higher-SES parents may be less likely to experience psychological problems themselves. They pass on genes conducive to better mental health to their children. Second, higher-SES parents may be better able to provide environments for their children
