Bidirectional Relationships in Hair Loss

I’m fascinated by the epidemiology of hair loss - especially the so called “bidirectional” relationships that existing among various hair disorders.

What is a bidirectional relationship? Well, if patients with disease A are more likely to develop disease B and patients with disease B are also more likely to develop disease A… then you are talking about a bidirectional relationship!

Let’s look at some examples from the world of hair loss.

COMMON EXAMPLES OF BIDIRECTIONAL RELATIONSHIPS IN THE FIELD OF HAIR LOSS

Alopecia Areata and the Risk of Depression

Alopecia Areata and Attention Deficit Hyperactivity Disorder

Alopecia Areata and Migraines

Alopecia Areata and Hypothyroidism

Alopecia Areata and Prurigo Nodularis

Alopecia Areata and Psoriasis

Androgenetic Alopecia and Sleep Disturbances

Frontal Fibrosing Alopecia and Rosacea

It makes some sense that patients with alopecia areata might have higher rates of depression. But who would have thought that patients with depression are more likely to develop alopecia areata!

Yes, a bidirectional relationship!

The same goes for migraines and attention defecit hyperactivity disorder (ADHD). Surprisingly, patients with migraines and ADHD are more likely to develop alopecia areata.

Bidirectional relationships have been studied in androgenetic alopecia too. Males with sleep disorders seem to be at risk for androgenetic alopecia and males with androgenetic alopecia are at risk for developing sleep disorders!

Yes, more fascinating bidirectional relationships!

Finally, the scarring alopecia research world is slowly uncovering many fascinating bidirectional relationships. For example, it’s well known that patients with FFA are more likely to develop the skin disease rosacea. But who would have thought that patients with rosacea would have an increased risk of developing frontal fibrosing alopecia.

Many more of these bidirectional relationships exist. The speak to the complex and overlapping pathogenesis of many of these disorders.

References

Liamsombut et al. Sleep and Breathing. 2022
Müller Ramos P et al. J Am Acad Dermatol. 2021.
Ho HY et al 2021.
Moreno-Arrones OM et al. Clin Exp Derm 2019.
Vallerand et al. JAMA Dermatol. 2019.

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Garate D et al. Bidirectional association between alopecia areata and prurigo nodularis: a population-based cohort study using TriNetX. Arch Dermatol Res . 2024 May 11;316(5):157