Recently, researchers in the field of conduct disorder (CD) have proposed including a specifier to the diagnosis of CD in DSM-5 based on the presence of callous-unemotional (CU) traits. Where does this idea come from, what is the evidence to support it, and why is it controversial? (Alphabet soup alert to readers: be forewarned that I will be using a lot of acronyms in this article, hopefully in the service of making the article more readable.)

Aggression in Disruptive Behavior Disorders

CD, along with oppositional defiant disorder (ODD) are known as disruptive behavior disorders. These disorders are often characterized by “bad,” typically aggressive, behavior. As we have noted in previous issues of CCPR, aggression can be driven by a host of things, such as PTSD, anxiety, mood problems (both depressed and manic), and ADHD. Common sense implies that when the underlying disorder remits, so will the aggression, and the experience of most clinicians bears that out.

This treatable type of aggression is classified as “REDI” aggression: Reactive, Affective, Defensive, or Impulsive. These are the impulses that lead to so-called crimes of passion. “Proactive aggression” is different, in that it is planned and calculated.

In practical terms, REDI aggression is much easier to treat than proactive aggression: it responds to many medications (see CCPR, May 2010) as well as psychosocial treatments. It tends not to be stable over time, and in most patients gradually fades away by early adulthood.

Proactive aggression, on the other hand, is extremely difficult to treat, and so the field has begun looking for ways to better understand people who engage in such behaviors.

The Significance of Callous-Unemotional Traits

To understand the concept of CU traits, you must first understand some of the modern ideas about CD. It turns out that there is a big difference between people whose CD begins in childhood and those whose CD begins in adolescence. In particular, childhood onset CD (COCD) is more severe than adolescent-onset CD (AOCD).

Kids with COCD are more likely to continue antisocial behavior into adulthood, and they have more neuropsychiatric and cognitive deficits, and more impulsivity and poor emotional regulation. COCD kids are also more likely to come from unstable homes and experience poor parenting strategies. Kids with AOCD, interestingly enough, are more likely to be rebellious and to reject conventional values, but beyond that they turn out “better” than their COCD counterparts.

The bottom line is that the earlier the CD begins, the worse the prognosis, which is not all that surprising to most of us. But the plot thickens, because within the group of COCD kids, there is an even more important dividing line, between kids who have high levels of CU traits and those who don’t. CU traits are defined broadly as “a callous and unemotional interpersonal style characterized by a lack of guilt and empathy and the callous use of others” (Frick P and Viding E, Devel Psychopathology 2009;21:1111–1131).

These CU traits can be measured in many different ways, but most commonly by combining aspects of self-assessment and parent-assessment questionnaires, such as the Antisocial Process Screening Device parts of ASEBA (Achenbach System of Empirically Based Assessment). Youths who score high on CU traits are not good at recognizing fear and distress in others (Frick P and White SF, J Child Psychol Psychiatry 2008;49(4):359–375). They are also less sensitive to punishment cues, and tend to have a fearless thrill-seeking and behaviorally uninhibited temperament (Cornell AH and Frick P, J Clin Adolesc Psychology 2007;36:305–318).

Conduct disordered kids with high CU scores tend to respond less well to treatment, and are more aggressive than other kids, showing both proactive and reactive aggression. In comparison, conduct disordered kids with low CU traits tend to have primarily reactive aggression, which is more treatable (Frick and White, op.cit).

Potential Causes and Interventions for Callous-Unemotional Behavior

Thus, the perfect storm for bad behavior and poor outcomes is the combination of COCD and high CU traits. What causes this devastating behavioral brew? This is where the controversy comes in. Some researchers have maintained that CU traits are biologically determined, while others argue that parenting factors lead to these traits. Yes, it’s one of psychiatry’s classic nature vs nurture debates.

Thus far, research findings can be interpreted in different ways. In one type of study, researchers begin with a cohort of COCD kids, and then measure temperament and retrospectively assess parenting styles. Such researchers tend to fall into the nature group, noting that studies of children with high levels of CU traits suggest that “this group of children may have a unique temperamental style, characterized by low levels of fear and lack of sensitivity to punishment” (Cornell and Frick op.cit). Others have started by measuring the quality of early bonding and attachment, and have concluded that poorly attached children are more likely to display antisocial behavior—the nurture viewpoint (see below: “Early Childhood Attachment and Conduct Problems” for more on this).

Those believing that the CU traits are an inborn temperament argue that these children have a harder time developing appropriate levels of guilt and empathy, because they are less likely to get bothered when punished or when they see that others are distressed. They advise that these kids may respond better to a more structured style of parenting. Why? Because research has shown that kids’ level of CU traits over time were more likely to decrease with more positive parenting, more parental involvement, and better monitoring and supervision (Hawes DJ et al, J Clin Child Adolesc Psychology 2011;40(4):507–518).