TLDR Hair diameter and curvature are mostly determined by genetics.
The study measured hair diameter and curvature in 2,332 Australian twins and siblings using an optical fiber diameter analyzer and found that these traits were highly heritable. Genetic factors accounted for 86% of the variance in hair diameter and 53% in curvature for males, and 77% in diameter and 61% in curvature for females. The consistency of hair diameter within individuals was also highly heritable (68%) without sex differences. There were moderate phenotypic correlations between diameter and consistency (r = 0.3) but little correlation between diameter and curvature (r = -0.13). Genetic correlations between hair diameter and consistency were r gF = 0.27 for females and r gM = 0.25 for males.
196 citations
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March 2016 in “Nature Communications” Genetic factors influence hair traits like shape, color, and greying in Latin Americans.
234 citations
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November 2009 in “American journal of human genetics” Common variants in the Trichohyalin gene are linked to straight hair in Europeans.
479 citations
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January 2005 in “BioEssays” Hair follicle development is controlled by interactions between skin tissues and specific molecular signals.
1113 citations
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August 1999 in “The New England Journal of Medicine” Hair follicle biology advancements may lead to better hair growth disorder treatments.
July 2008 in “British Journal of Dermatology” Cyclosporin doesn't stop hair loss.
4 citations
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June 2021 in “Scientific Reports” Hair fiber shape and curvature are not significantly linked when ancestry is considered.
12 citations
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July 2016 in “British journal of dermatology/British journal of dermatology, Supplement” Different hair fiber development might explain why hair loss severity varies in patients with a specific genetic mutation, and treatments that thicken hair could help.
28 citations
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November 2018 in “Journal of structural biology” Different populations have distinct hair structures related to their ancestry.
Afro-textured hair is more fragile and prone to certain scalp conditions, requiring careful treatment and more research for effective management.
