Study Guide with article summaries for Violence and the brain at the University of Leiden

What is conduct disorder (CD)?

Conduct disorder is a psychiatric disorder that often emerges in childhood or adolescence and is characterized by behaviors that violate the rights of others, such as physical aggression towards people or animals, theft, rule violations, and property damage. It often co-occurs with ADHD and often leads to antisocial personality disorder in adulthood. The disorder can be subtyped based on age at onset (childhood versus adolescent onset) and the presence/absence of callous-unemotional traits (deficits in empathy and guilt). 

Why is it difficult to diagnose conduct disorder?

The diagnostic criteria for conduct disorder are entirely based on behavioral symptoms. Therefore they say nothing about the underlying cognitive or emotional processes that drive the symptoms. It is also a highly heterogeneous disorder. Many different symptom profiles could lead to a CD diagnosis and different symptom clusters have different developmental trajectories and causes.

What are callous-unemotional traits?

The diagnostic criteria for CD include subtypes based on the age of onset of symptoms and the presence or absence of limited prosocial emotions (LPEs). The symptoms defining LPEs, which include deficits in empathy, are labelled the affective dimension of psychopathy, or callous-unemotional traits.

What causes conduct disorder?

The aetiology of CD is complex, with contributions of both genetic and environmental risk factors and different forms of interplay among the two (gene–environment interaction and correlation). Environmental risk factors may be more or less important depending on the developmental stage, whereas genetic risk factors tend to exert their effects across all developmental stages.

Which environmental risk factors are at play in conduct disorder?

Many environmental risk factors have been identified for conduct disorder. These risk factors are not specific for conduct disorder and it is unclear whether there are causal connections or just associations, nor are the underlying mechanisms well understood. Either way, the identified risk factors are:

• Prenatal risk factors: smoking, alcohol, drug use, and stress.

• Perinatal risk factors: birth complications, maternal or paternal psychopathology, malnutrition, and exposure to heavy metals.

• Familial risk factors: harsh and inconsistent discipline, parent-child conflict, maltreatment, and low socio-economic status and poverty.

• Extra familial risk factors: community violence, and association with deviant peers.

Which genetic risk factors are at play in conduct disorder?

Conduct disorder is not a unified construct in terms of its genetic architecture. The genetic contribution to CD increases from childhood to adolescence, but it is not stable over time. This suggests that partly different genes contribute to CD at different stages of the lifespan. Genetic risk factors at play are autonomic, neurocognitive, and those to do with social information processing, temperament, and personality traits.

What is the role of gene-environment interplay in the development of conduct disorder?

Gene-environment interaction refers to whether genes moderate the effects of positive or negative environmental influences. Conduct disorder has a complex, multifactorial aetiology that is characterized by polygenic inheritance and genetic heterogeneity across individuals, supplemented by the effects of environmental factors that may interplay with genetic factors at any point during development.

What are gene-environment correlations in conduct disorder?

• Passive gene-environment correlation occurs when children inherit genetic variants that also contribute to the environment that the parents create. For example, a child that inherits genes that increase the risk of psychopathology.

• Active gene-environment correlation occurs when the child’s genes predispose them to seek out certain environments. For example, a child seeks out dangerous environments, increasing their risk of developing conduct disorder.

• Evocative gene-environment correlation occurs when the child’s genes predispose them to behave in a way that evokes certain environmental influences. 

What brain mechanisms are identified in conduct disorder?

With regard to the brain and brain development, the following has been discovered to be associated with conduct disorder:

• Neurocognitive impairments.

• Smaller grey matter volume in limbic regions such as the amygdala, insula, and orbitofrontal cortex.

• Functional abnormalities in overlapping brain circuits responsible for emotion processing, reinforcement-based decision-making, and emotion regulation.

• Lower hypothalamic-pituitary-adrenal axis and autonomic reactivity to stress.

How can conduct disorder be treated?

Effective management of conduct disorder aims to reduce the core symptoms, improve emotion regulation, enhance moral development and social skills, and reduce symptoms of comorbid psychiatric and developmental disorders. This treatment relies on mental health professionals and services. Lasting change is most likely when parents/primary caregivers are involved. In late childhood/adolescence it seems that multicomponent treatments that integrate family strategies, cognitive-behavioral therapy, and behavioral strategies are the most effective. In individuals with comorbid ADHD, stimulants and atypical antipsychotics can be used.