COPENHAGEN – The physiological and emotion-processing abnormalities that underpin conduct disorder in teen girls are essentially the same as in teen boys, although the clinical presentation of conduct disorder in the two groups is often different, according to preliminary results from the large pan-European FemNAT-CD study, the first large study of conduct disorder in girls.
Bruce Jancin/MDedge News
Dr. Lucres Nauta-Jansen
“The main finding of the study, I think, is that we found no major differences in physiology between male and female conduct disorder. There are some differences, mainly related to having less LPE [low prosocial emotions] and more internalizing comorbidity in the girls, but when you look at conduct disorder overall, then you see that the physiological systems are about the same,” Lucres Nauta-Jansen, PhD, commented in presenting some of the early FemNAT-CD findings at the annual congress of the European College of Neuropsychopharmacology.
LPE is a term included in the DSM-5 as a descriptor of individuals with conduct disorder (CD) who exhibit callous-unemotional traits. The LPE specifier was present in 37% of the 296 adolescent girls with CD in FemNAT-CD, significantly less than the 50% prevalence in the 187 adolescent boys with CD in the study. This analysis from the ongoing study, which is being conducted at 13 universities across Europe, also included 363 age-matched girls and 164 age-matched boys without CD as controls. Average participant age was 14 years.
FemNAT-CD is a multidisciplinary study aimed at exploring sex differences between boys and girls with and without CD in terms of brain structure and function, genetics, hormone levels, emotion recognition and regulation, and autonomic nervous system (ANS) activity. At Amsterdam University Medical Center, where Dr. Nauta-Jansen serves as deputy head of the department of child and adolescent psychiatry, she and her coinvestigators have focused on the autonomic activity and emotion-processing portions of FemNAT-CD.
CD is less common in girls than boys, although the prevalence in girls is growing. The importance of FemNAT-CD lies in the fact that virtually all prior studies of CD were conducted in boys. As a result, there is no specific treatment intervention available for girls with CD.
“We actually don’t know anything about girls. There are a few previous studies, but they have small samples and contradictory results. We need to know more about the mechanisms that are involved in this kind of behavior to develop more specific treatments in the future,” Dr. Nauta-Jansen said.
In FemNAT-CD, the girls with CD not only had a lower rate of LPE symptoms than the boys with CD, they also had a significantly higher prevalence of anxiety and other internalizing comorbidities, by a margin of 32% to 22%. These differences are manifested in different expressions of antisocial behavior as described in the model of the neurobiology of CD developed by R. James Blair, PhD, director of the Center for Neurobehavioral Research at the Boys Town National Research Hospital in Omaha, Neb (Nat Rev Neurosci. 2013 Nov;14[11]:786-99).
According to the model’s low psychophysiological arousal theory, boys with the callous-unemotional form of CD have low basal ANS activity and low amygdala responsiveness to stressful events, making them more prone to sensation-seeking behavior.
“This might make them want to do ice climbing or sky diving. Or, in a more negative environment or in a bad neighborhood, it can also lead to aggressive and delinquent behavior,” Dr. Nauta-Jansen said.
The other core impairment that is common in a subset of CD patients as described in the Blair model – again, based upon studies in boys – involves a tendency to engage in threat-based reactive aggression with an increased ANS response to stress and a related difficulty in processing emotions.
Dr. Nauta-Jansen and coinvestigators conducted a series of tests of FemNAT-CD participants which demonstrated, for the first time, that both the callous-unemotional and threat-based reactive aggression forms of CD are present in girls as well as boys, albeit in different proportions.
The investigators found no differences in baseline ANS activity between girls and boys with CD and the controls as measured by heart rate, heart rate variability, and cardiac preejection period. Nor were there any differences in baseline ANS activity between boys and girls with CD and LPE. However, girls with CD and anxiety or other internalizing comorbidity displayed significantly lower heart rate variability than those without internalizing comorbidity or female controls.
Next, the investigators subjected study participants to an emotion provocation task in which they viewed two sadness-inducing film clips, including a heart-rending scene from the 1979 movie, “The Champ,” in which an ex-boxer played by Jon Voight returns to the ring to raise money to support his young son, played by Ricky Shroder. The champ wins by a knockout after taking such a beating that he subsequently dies in his dressing room as his son watches.
Both the girls and boys with CD had an increased heart rate response to “The Champ,” compared with the controls. And those with CD who did not have the LPE specifier showed the biggest ANS response of all. They were highly sensitive to negative emotions.
On a countdown task involving exposure to a loud, startling noise, the girls with CD did not learn to anticipate the pending startle at the autonomic level, whereas the boys with CD reacted no differently from controls.
On the Trier Social Stress Test, which entails public speaking and performing mental math calculations in front of a camera and a live audience of two, both the boys and girls with CD demonstrated a similarly lower heart rate response to the tasks than controls. Those with the LPE specifier had the lowest heart rate response of all.
“The conduct disorder subjects were impaired in their anticipatory response to fear and stress, but their responses to sadness were increased,” Dr. Nauta-Jansen observed.
“I think the main thing with these kids is they are mostly disturbed in their anticipation of bad situations. What you see in the countdown task is they don’t anticipate that there will be a bad event. And you see this also in clinical practice, that they sometimes get overwhelmed by things because they don’t learn from their previous experiences, including bad events. I think they don’t anticipate and therefore are more overwhelmed by bad events – especially the girls,” she said.
The take-home message from this phase of the FemNAT-CD study, she added, is straightforward: “ although you have to be very aware that they show different symptomatology in terms of internalizing comorbidity.”
The FemNAT-CD investigators have developed a multifaceted therapeutic intervention for girls with CD that shows early promise in clinical settings. It includes aggression regulation training, medication in some cases, and emotion-processing training to teach patients how to deal with negative emotions without exploding into aggression.
FemNAT-CD is funded by the European Commission. Dr. Nauta-Jansen reported having no financial conflicts regarding the study.