The shape of the forehead, formed by the frontal bone of the skull, varies widely among people. A “flat” forehead refers to a profile that is less rounded or prominent than average. This contour is a normal variation in human anatomy and is not usually a cause for concern. The reasons for this shape involve genetics, external forces during infancy, and changes that occur as the face matures.
Inherited Traits and Skull Architecture
The primary determinant of forehead shape is the genetic information inherited from one’s parents. Genes contain the instructions for the size, shape, and angle of the frontal bone, establishing the fundamental architecture of the upper face. A significant portion of your forehead’s contour is predetermined by this genetic blueprint.
The appearance of a flatter forehead often relates to the structure of the supraorbital region, specifically the prominence of the brow ridges (superciliary arches). These bony ridges are located just above the eye sockets. A less pronounced or less forward-projecting brow ridge can make the forehead above it appear more vertical or flat in profile.
This variation in brow ridge prominence is influenced by biological sex, with males generally exhibiting more pronounced ridges than females due to hormonal influences on bone structure. The overall contour of the frontal bone is ultimately dictated by these inherited skeletal features. Specific genes, like RUNX2, play a role in coordinating skull development and can have localized effects on the central forehead.
Positional Factors in Infancy
While genetics establish the blueprint, external forces can significantly mold the skull during infancy when the bones are still soft and rapidly growing. This acquired flatness is often referred to as “flat head syndrome,” which encompasses positional plagiocephaly and brachycephaly. The skull is particularly malleable during the first few months of life.
The recommendation for infants to sleep on their backs to prevent SIDS means they spend prolonged periods with pressure on the back or side of the head. Positional plagiocephaly results in asymmetrical flattening on one side of the back of the head, sometimes causing the forehead and cheek on that side to shift slightly forward. Brachycephaly involves central flattening across the entire back of the head, making the head appear wider and shorter.
Although these conditions primarily affect the back of the skull, the resulting shift in cranial shape can influence the forehead’s appearance. Positional deformities typically cease to progress once a child begins to sit up and spends less time lying down. The resulting contour can persist into adulthood, even though the impact of these early environmental factors stops after infancy.
Craniofacial Growth and Maturation
The skull undergoes differential growth that continues from childhood through early adulthood, rather than expanding uniformly. While much of the craniofacial growth is complete by age seven, subtle changes continue for many years. Final size maturity is typically attained between ages 13 and 15 in females and 17 and 25 in males.
During adolescence, the lower face, including the nasal bone and the jaw, experiences significant growth spurts, especially in males. This differential growth changes the perceived projection of the forehead relative to the rest of the face. The forward growth of the mid-face and jaw can make a stable forehead contour appear less prominent in profile simply due to the forward shift of the features below it.
Beyond bone structure, the distribution of soft tissue, such as subcutaneous fat, also influences the perceived contour of the forehead. Changes in fat volume and distribution, which occur with age and weight fluctuations, might alter the surface appearance of the forehead, making it seem flatter or rounder. In rare cases, a markedly unusual forehead shape can be related to craniosynostosis, where the skull sutures fuse prematurely. This condition is typically detected and treated in infancy due to its potential to affect brain development.