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The Core Phenotype
The Core phenotype is a clinical subtype of pediatric bipolar disorder (PBD) based on the presence of a particular trait that investigators of the JBRF Research Consortium call Fear-of-Harm (FOH). Delineation of this phenotype is the result of investigators focusing on the presentation of anxious fears and aggressive behaviors exhibited by children with bipolar disorder. Their clinical experience confirmed for them that these behaviors were prevalent and concerning issues. A 2001 National Institute of Mental Health directive expressed that same concern.
The exploration of these behaviors was driven by data collected by the JBRF. The JBRF website provides a portal through which investigators gather data about children with a community diagnosis of bipolar disorder or at risk for the disorder. The families of several thousand of these children submitted information on two important and well validated screening questionnaires: (1) the Yale Brown Obsessive Compulsive Scale (YBOCS) which measures anxiety and obsessive-compulsive behaviors and thoughts, and (2) the Overt Aggression Scale (OAS) which measures aggression directed towards self and others.
Investigators focused on six aggressive obsessions from YBOCS that constitute what they call Fear-of-Harm. They are:
Children can experience these fears overtly and/or continuously under the surface. A correlation study demonstrated that, for this pool of children, a strong positive correlation exists between these fearful feelings and aggressive behavior; as the measure of FOH increased, so too did the degree of aggressive behavior.
This relationship may seem counterintuitive. Indeed, it was not found to exist in healthy children. However, for children in a bipolar population, the data was compelling. In regards to the two most severe measures of aggression on the OAS,
children with high FOH were found to be 2.7 times more likely to inflict that kind of harm on themselves and 8 times more likely to inflict that kind of harm on others. (Of note: as children age there is a significant shift from directing harm towards others to directing harm towards self.) In addition to its strong correlation to aggression, FOH was also found to have high correlation to threats of suicide.
The presence of FOH falls in a spectrum as do most psychiatric features. Certainly not all children who have this trait will exhibit the kind of aggressive behavior listed above. Aggression can range from cursing and head banging to threats and hitting to extreme, injurious behaviors. Later studies showed that approximately 1/3 of the children with a community diagnosis of bipolar disorder or at risk for the disorder, do not have FOH. Approximately 1/3 of these children have what investigators call low FOH and 1/3 have high FOH. A child’s level is determined by how many of those 6 YBOCS behaviors he or she experiences often or almost always.
FOH was found to be a highly heritable trait. That heritability makes investigators consider it as the basis for a subgroup of the disorder which they have called the Core phenotype. In order to develop a single, easy to use screening instrument to identify this subgroup, they identified the 22 items from the Child Bipolar Questionnaire (CBQ) which would incorporate the FOH trait and its associated symptoms. The specialized list of CBQ items is called the Core Index. When tested for heritability, this index of symptoms was found to be highly heritable. A scoring algorithm designed for the CBQ can rapidly determine if a child meets the Core phenotype threshold (Click here for the CBQ instrument).
The relationship between FOH and aggression has important clinical implications. The prescription of anti-depressant medication, otherwise appropriate to treat obsessive fears, may be reconsidered for an intensely fearful, aggressive child with abrupt, rapid mood changes. Suicide risk might also be closely monitored in such children.
This information is based on articles published in The Journal of Affective Disorders as linked below:
Obsessive fears about harm to self or others and overt aggressive behaviors in youth diagnosed with juvenile-onset bipolar disorder
Fear of harm, a possible phenotype of pediatric bipolar disorder: A dimensional approach to diagnosis for genotyping psychiatric syndromes
A strategy for identifying phenotypic subtypes: Concordance of symptom dimensions between sibling pairs who met screening criteria for a genetic linkage study of childhood-onset bipolar disorder using the Child Bipolar Questionnaire
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About Juvenile-Onset
Bipolar Disorder
According to JBRF Sponsored Research
Approach and Definition
The Core Phenotype
The Fear of Harm Phenotype
Symptoms of the Fear of Harm Phenotype
The 6 CBQ Dimensions of Behavior
FAQs
Suggested Links
Suggested Readings
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