You don’t need to check their hormone levels to know that most children are stressed out when they start school.

A UK research team, led by Julie Turner-Cobb of the University of Bath, wanted to know a bit more about the characteristics of this stress. So they collected the saliva of four-year-olds several months before they entered school, again upon their entrance and then six months later. The saliva was examined to determine their cortisol levels. The more cortisol present, the more stressed out the children probably are.

Turner-Cobb and her colleagues predicted that children would become more stressed as they entered school and then calm down as they adjusted to their new environment. They also speculated whether some kids would do better than others. For instance, might children with strong social skills be less jittery about the school transition?

To help them answer such questions, 105 four-year-olds starting primary school in South West England provided their saliva samples, and their parents and teachers provided information on the new students’ temperament and behavior.

The researchers found that the children’s cortisol levels were fairly high several months before they even started school. Indeed, the children seemed about as stressed out at this point as they were on the first day, perhaps because they were already anticipating the change – or because they were reacting to their parents’ anticipation.

As predicted, the children tended to relax as the school year progressed and generally had lower cortisol levels six months after the start.

Turner-Cobb and company found that the children who appeared to handle the transition best were those described by their parents as tending to be sad, angry, frustrated, or fearful. By contrast, children described as intense or impulsive had a harder time, particularly those who lacked friendships at school. This latter group (kids who were both intense and social isolated) had high cortisol levels even after six months of school.

The researchers don’t attempt to explain why sad or angry kids might find it easier to get used to school than other children nor why intense kids find it harder. They do, however, note that helping students to be involved with their peers may help to reduce the stress, at least for some.

• Summary of “A prospective study of diurnal cortisol responses to the social experience of school transition in four-year-old children: Anticipation, exposure, and adaptation” by Julie M. Turner-Cobb, Lorna Rixon, and David S. Jessop in Developmental Psychobiology, April 2008, Volume 50, Issue 4, pp 377-389.