- FOH is a hereditary condition
- The likelihood of acquiring the trait increases when the family history is rich with brain disorders (diagnosed or not) and/or alcoholism
- Approximately 2/3 of people who might get a diagnosis of bipolar disorder have some degree of FOH
- Across the bipolar spectrum, it is reasonable to estimated that over 10 million adults and children in the US have some degree of the FOH trait.
Who Is Susceptible?
FOH is based on a heritable trait. This means that the condition is the result of genetic predisposition rather than the product of the environment or life experiences. Of course both of these things effect the course of the condition, but the illness precedes these things and forms the base with which the child makes his/her way through life. Like the name given to the syndrome; Fear of Harm, the trait itself has also been labeled fear-of-harm.
Because the trait is heritable, children who are born into families whose members struggle with various mental health issues are more likely to be affected than those who are not; particularly if the mental health difficulties come down both side of the family. Since many people have not sought mental health support and because, even for those who have, the diagnoses are not very reliable; it is not necessary that the family history have any known or particular diagnoses in order to be a candidate for the trait. Often people have heard that Great Grandpa So-and-So was over controlling and abusive, Aunt So-and-So acted unpredictably and kept to herself, or Dad suffers with alcoholism (a particularly strong association), etc. The stronger the family history: the more likely it is that the trait is there to some degree or another.
How Many People Have FOH?
When thinking about who might have FOH, it is important to remember that, even though the line of research which delineated FOH started out trying to understand more about bipolar disorder in children, FOH is not a subtype of bipolar disorder (see FOH v. Bipolar Disorder). Therefore, in order to fully understand who might have FOH, you need to wipe the slate clean of prior ideas and categories (see What is a Brain Disorder) and assume that, among all people, quite a few of them will be carriers of the genes that create this trait.
Certainly, the prevalence among people who have a diagnosis of bipolar disorder will be higher than among the general population; they have already been identified as having some of the symptoms of FOH. But even within that community, not everyone has the trait which causes FOH. Investigators determined that among almost 2,000 children who were at risk for, or diagnosed with bipolar disorder, it so happens that;
- 1/3 of them did not have the trait.
- 1/3 of them had what investigators call LowFOH. (This means that the genetic loading for the trait results in a more mild expression of the condition. Despite the fact that it is a more mild presentation, it is still very impairing.)
- 1/3 of them had HighFOH; (This suggests a stronger genetic loading of the trait which results in a more extreme expression of the condition).
(Age was not a relevant factor between groups. While there were an equal number of boys as girls in the combined FOH groups; there were more boys than girls in the LowFOH group.)
If we take this distribution and apply it to the entire bipolar spectrum community, there could be as many as 9 million adults and 2 million children who have some degree of the fear-of-harm trait.
Further, other people also have the trait. People who have not been diagnosed with any bipolar diagnosis but have been diagnosed with other disorders such as OCD, ADHD, depression, conduct disorders, anxiety disorders, etc. also have an increased likelihood to have the trait. No prevalence rates have been estimated for people with these other disorders or for people with no disorders.
 According to a 2007 National Institute of Mental Health study, there is a 4.5% lifetime prevalence rate in the US for the bipolar spectrum disorders. That translates into over 14 million people with BP I, II or NOS. (Prevalence of just BP I and II in 2013 are 5.7 million people.) If the distribution described above is even close to accurate, then it is reasonable to assume that, from this community alone, over 9 million adults have some degree of FOH. The prevalence rate for bipolar spectrum disorder among children is similar. That would mean that over 2 million children have some degree of the FOH trait. The previous statements are based upon the following references:
Merikangas KR, Akiskal HS, Angst J et al. (2007) Lifetime and 12-month prevalence of bipolar spectrum disorder in the national Comorbidity Survey replication. Arch Gen Psychiatry. 2007 May; 64(5): 543-52.
National Institute of Mental Health, The Numbers Count: Mental Disorders in America, http://www.nimh.nih.gov/health/publications/the-numbers-count-mental-disorders-in-america/index.shtml#Bipolar (June, 2013)
Lewinsohn PM, Klein DN, Seeley JR: (1995). Bipolar Disorders in a Community Sample of Older Adolescents: Prevalence, Phenomenology, Comorbidity, and Course. J Am Acad Child Adolesc Psychiatry, 34:4 pp 454-463