I bet every single person who has trichotillomania, once they realize it is a disorder, wonders if they inherited it. Pondering a genetic predisposition is an interesting way to spend an afternoon, as it turns out. There’s a lot of different opinions in the scientific community about trichotillomania being genetically-linked or not. So, for all of those out there wondering if you inherited it or not, or if you passed a part of the trich code to your children, here’s what the scientific literature says.
Genetic Predisposition #1: Inheritance Modes
According to the U.S. Department of Health & Human Service’s National Institute of Health (NIH) and the Genetic and Rare Disease (GARD) Information Center’s trichotillomania page, trich is classified by their information database, called the Human Phenotype Ontology (HPO), as having both autosomal dominant inheritance and multifactorial inheritance.
- Multifactorial inheritance: A mode of inheritance depending on a mix of minor and major genetic determinants, possibly together with environmental factors. Diseases inherited in this way are called complex diseases.
- Autosomal Dominant Inheritance: A mode of inheritance related to gene-encoded traits on one of the autosomes (human chromosomes 1-22) whereby the trait manifests in heterozygotes. This is caused when a single copy of the mutant allele is present. Males and females can be impacted equally, with the risk of transmitting to children at 50%.
Genetic Predisposition #2: Trichotillomania in Twins
To date, there have been two separate studies comparing the presence of trich between monozygotic/identical (sharing 100% of genes) and dizygotic/fraternal (sharing 50% of genes) twins. These are important studies for testing hereditary rates for trich.
Both studies found a significant difference in trich occurrence between the two twin types, based on the DSM-IV criteria for trich.
- American Journal of Medical Genetics: The study found that the different types of twin pairs, identical and fraternal, had significant differences in their trich presentation. Identical twins had 58.3% trich representation, while fraternal twins had 20% trich representation, for a total of 76.2% trich heritability for all twins in the study. Given the strong correlation, this suggests that genetic inheritance factors play a significant role in the presentation of trich.
- Journal of the American Medical Association for Psychiatry: The twin study found that heritability was 31.6% for trichotillomania. Interestingly, it also found that risk factors unique to the twin set’s environment appeared in 55% of the trich cases. This lends some credence to the idea that shared environmental factors may also play a marginal role in the formation of trich.
Genetic Predisposition #3: First-Degree Relative Rates
Various studies have explored the presence of trich in first degree relatives (parents, siblings and children). Here are their findings:
- The American Journal of Psychiatry: Several trich cases were analyzed. It was found that 8% of trichsters had first-degree relatives who also had trich.
- Annals of Clinical Psychiatry: The study found that, on average, 5% of the trichster’s first-degree relatives also had trich.
- German Journal of Psychiatry: A young girl with trichotillomania had a family history with her mother also having trich.
- Journal of Child Psychology and Psychiatry: While exploring the relationship between trich and OCD, the study found that 19% of the trichsters had first degree relatives with OCD. This supports the idea that trich families have higher rates of OCD and other pathological grooming behaviors.
Obviously, there is one huge factor which isn’t really explored here, which is whether it may be a learned behavior from those around the trichster. Unfortunately, that is so incredibly hard to scientifically test. The ideal situation would be a twin study of twins separated early on who grew up in completely different circumstances. But, that doesn’t exist. Just keep in mind that the environment may also play a role as well as genetics.
While this is by no means an exhaustive list, I do think that the findings are pretty conclusive. It appears that trich does have mild to intermediate associations with hereditary inheritance, as shown by twin and first-degree relative occurrences. For more on the subject, I recommend this review article published by the Indian Academy of Sciences.
In My Own Life
Personally, my father falls along the OCD spectrum while my mother has skin-picking/excoriation disorder and my sister is a massive hair twirler. It makes sense in my own familial occurrences that genetic inheritance has played some role.
I hope that this exploration of the available scientific studies has helped to inform you in some way. I’d love to hear your own thoughts on the matter so feel free to leave a comment if you want. I’d love to hear from you.
American Journal of Medical Genetics, “A Twin Concordance Study of Trichotillomania”
The American Journal of Psychiatry, “Familial Trichotillomania”
Annals of Clinical Psychiatry, “The Demography, Phenomenology, and Family History of 22 Persons with Compulsive Hair Pulling”
Genetic and Rare Diseases Information Center (GARD), Trichotillomania
German Journal of Psychiatry, “Familial Trichotillomania Responding to SSRIs”
Human Phenotype Ontology (HPO), Autosomal Dominant Inheritance
Human Phenotype Ontology (HPO), Database
Human Phenotype Ontology (HPO), Multifactorial Inheritance
Indian Academy of Sciences, “The Genetic Factors Influencing the Development of Trichotillomania”
Journal of the American Medical Association for Psychiatry, “The Structure of Genetic and Environmental Risk Factors for Dimensional Representations of DSM-5 Obsessive-Compulsive Spectrum Disorders”
Journal of Child Psychology and Psychiatry, “Rates of Obsessive Compulsive Disorder in First Degree Relatives of Patients with Trichotillomania”
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