How was the Fear-of-Harm Trait Defined?
Two concurrent lines of inquiry informed investigators of the fear-of-harm trait. A third line of inquiry proved its importance by revealing its strong heritability:
Investigators used two questionnaires: the Yale-Brown Obsessive Compulsive Scale (Y-BOCS) and the Overt Aggression Scale (OAS).
Y-BOCS reports submitted by 1,600 parents of affected children allowed investigators to learn more about the presence of six aggressive obsessions within the bipolar population. They are:
- Fear might harm self
- Fear might harm others
- Fear harm might come to self
- Fear harm might come to others (may be because of something the child did or did not do)
- Fear will act on unwanted impulses
- Fear will be responsible for something else terrible happening (i.e. fire, burglary)
Based on the answers to these six questions, investigators divided the children into two groups: those with low fear-of-harm and those with high fear-of-harm.
Next, investigators looked to see how this group of symptoms correlated with the aggressive behaviors listed on the OAS questionnaire. The investigators found a strong positive correlation between the obsessions and the behavior. The higher the fear-of-harm score, the more likely the association with the most severe aggressive behaviors from OAS. Those behaviors are:
- Mutilates self, causes deep cuts, bites that bleed, internal injury, loss of consciousness, loss of teeth
- Attacks others, causing severe physical injury (broken bones, deep lacerations, internal injuries)
Children with high fear-of-harm were 2.7 times more likely to inflict the above mentioned type 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 the direction of harm towards others to the direction of harm towards self.) Additionally, the trait was found to have a high correlation to threats of suicide.
This does not mean that all children with fear-of-harm will cause severe injury to self or others; but it does establish a relationship between fearful obsessions and aggressive behavior.
Investigators conducted dimensional analyses (click here to read about dimensional analysis) on the Child Bipolar Questionnaires (CBQ) sent in by the parents of almost 3,000 children. (Click here to view the CBQ.) The CBQ includes symptoms of bipolar disorder as well as the broad range of symptoms included in the diagnoses considered co-morbid with bipolar disorder: mania, major depression, separation anxiety disorder, generalized anxiety disorder, obsessive-compulsive disorder, oppositional defiant disorder, conduct disorder and attention deficit disorder.
The dimensional study clustered those symptoms into ten dimensions of behavior. (Click here to see those ten dimensions). Of those ten, one of the dimensions prompted the label of fear-of-harm. The symptoms that clustered into that dimension include:
- Displays excessive distress when separated
- Exhibits excessive anxiety or worry
- Has night terrors and/or nightmares
- Displays aggressive behavior towards others
- Has destroyed property intentionally
- Makes moderate threats to others and self
- Makes clear threats of violence to others/self
The emergence of this same characteristic, derived from a different data base, bolstered the findings of the importance of fear-of-harm.
The importance of the fear-of-harm trait became further solidified when investigators conducted an analysis to determine the degree of heritability of each of the ten dimensions. This was done by a comparison of the presence of each dimension between siblings to the presence of each dimension between similarly comparable children who were not siblings. The fear-of-harm dimension was the hands down winner; 9 times more heritable than any other dimension. While the dimensions of mania and depression also emerged from the dimensional analysis, they were significantly less important from a heritability point of view than the fear of harm dimension. While mania and depression may be easier to observe, if the goal is to understand the physiological condition that creates the illness, it would be more fruitful to focus on fear-of-harm.
The fact that the fear-of-harm trait is highly heritable does not unto itself validate a phenotype; however it does provide indication that looking at the problem in a dimensional way could be more productive than trying to understand the condition in terms of episodic mania and depression.