The study conducted the University of Helsinki, Finland suggested that the origin of hostility lies in the low fetal and postnatal development. The scientists analyzed the data of 939 women and 740 men born in Helsinki between 1934 and 1944, their development from birth, child well-being and school records and their body size during adulthood. The participants also had completed a test measuring the level of hostility called the Cook-Medley Hostility Scale at an average age of 63.4 years.
The results of the study showed that participants with higher levels of hostility had lower weight at birth and lower weight gain from birth to 6 months. Their weight gain increased only in adulthood.
These individuals also were shorter in the first year of life and adulthood, which was explained by slower growth during the first 6 months after birth.
It is known that high hostility levels may indicate the increased risk of cardiovascular disease and mortality. Dr. Katri Raikkonen, who led the study said that trajectories of growth of people with higher levels of hostility was similar to those when people have certain health conditions such as stroke, coronary disease, type 2 diabetes in adulthood.
Researchers say that other factors like mother's age, number of brothers or sisters, educational level or breastfeeding were unrelated to these findings, while fetal and postnatal development turned out to be crucial for high levels of hostility.