3 Child mental health and development
3.3 Developmental achievements during the middle childhood
The middle childhood, ages from six to twelve years, has sometimes been described as the ‘forgotten years’ of childhood, as the great majority of research has focused either on the early childhood or the adolescence (Mah & Ford-Jones, 2012). Yet, middle childhood is rich in potential for physical, cognitive, social, and emotional achievements (Cole, Cole, & Lightfood, 2005). Physically, children at this point get stronger and more coordinated, making it for them possible to succeed in a variety of athletic hobbies. Cognitively, they become more able to abstract thought processes that can concern for instance the future and their place in it. Socially, they begin to show more independence from their parents and family, whereas friends and their acceptance becomes more important. Emotionally, they become increasingly aware of their own as well as others’ experiences, feelings and thoughts, and develop more empathy, altruism and moral. All these rapidly developing skills make the middle childhood an important developmental phase that can build a strong foundation for adulthood (Boyd, 2012).
At the same time, children in middle childhood can experience these developmental expectations as stressful: they may feel insecure about having to grasp more autonomy from their parents, become distressed by complicated frienships and social networks, or face difficulties in coping with academic challenges. In line with this, mental health problems in middle childhood, involving both internalizing and externalizing symptoms, have shown to affect as much as 22% of Finnish children, with boys displaying more problems than girls (Almqvist et al., 1999). Nine percent of the children were in urgent need of treatment and a fourth in need of clinical assessment. Concerning social developmental risks, nearly a fifth of children appear to be involved in bulling at school (Yang & Salmivalli, 2013), and approximately 10-15% of children feel rejected, chronically lonely and have no friends (Asher &
Paquette, 2003). Finally, cognitive developmental problems and learning disabilities,
including difficulties in language, math, memory and executive functions, have been estimated to affect about 10% of children (Johnson, 2017).
Importantly, optimal developmental achievements during the middle childhood are induced by development and maturation of the central nervous system. First, myelination occurs within the corpus callosum and subcortical areas, enabling faster synaptic transmission between the hemispheres and thus more advanced motoric, cognitive and emotional abilities (Rappley & Kallman, 2009).
Second, significant adaptation happens in cortical gray matter, which also endorses cognitive development (Mah & Ford-Jones, 2012). Third, brain development in middle childhood relates mostly to the pruning of synapses (Rappley & Kallman, 2009). Thus, the increasing motoric, cognitive and psychosocial capacity across the middle childhood is likely to reflect a gradual loss of synapses, rather than formation of new ones. Selectivity in the pruning leads to a strengthening of the remaining synaptic connections and a suppression of competing irrelevant connections and behaviors. Therefore, with age, fewer and more select regions of the brain become activated in response to a specific stimulus, thus enabling faster and more efficient overall functioning (Chechik, Meilijson, & Ruppin, 1998).
Children’s physiological stress regulation develops and matures in middle childhood, becoming relatively adult-like (Gunnar & Donzella, 2002). Importantly, HPA-axis regulation in middle childhood can be indicated by the level of cortisol in saliva or circulation, or by the daily diurnal cortisol pattern. Dysregulated cortisol levels can indicate either hypersecretion or hyposecretion. Hypersecretion is suggested to reflect a currently stressed, hyperactive HPA (McEwen & Wingfield, 2003), whereas hyposecretion relates to reduced cortisol production, possibly due to more chronic stress that has caused ‘exhaustment’ of the mechanisms underlying HPA (Doom, Cicchetti, & Rogosch, 2014; Fries, Hesse, Hellhammer, &
Hellhammer, 2005). However, as cortisol secretion fluctuates significantly across day and night, measurements of cortisol level are considered less sensitive markers of dysregulation than the measures of diurnal patterning (Sharpley, Kauter &
McFarlane, 2010).
Diurnal pattern, the fluctuation in the amount of secreted cortisol throughout the day, reflects the ongoing change in the need of a person to be alert versus relaxed.
Similarly to adults, typical cortisol pattern among school-aged children involve lowest secretion around midnight or wee hours, and an intense trend upward towards morning. The secretion reaches its peak approximately 30 min after awakening but remains elevated for at least another half an hour. This change in cortisol across the first hour after waking from sleep is called the cortisol awakening
response (CAR) (Fries, Dettenborn &Kirschbaum, 2009). Thereafter, towards midday, afternoon and especially evening, the secretion decreases, which has been called the diurnal cortisol decline (DCD) (Edwards, Clow, Evans & Hucklebridge, 2001).
Importantly, children’s HPA-axis dysregulation – measured through less than optimal cortisol levels or diurnal patterns - is known to exert harmful effects on the functioning and development of vital brain regions such as the hippocampus, the amygdala and the frontal cortex (Carrion, Weems & Reiss, 2007; Frodl & O’Keane, 2013). Presumably mediated by these detrimental neural effects, cortisol dysregulation increases vulnerability to cognitive problems in learning and memory (Heffelfinger & Newcomer, 2001). Furthermore, it jeopardizes children’s ability to regulate their behavior and emotions through non-optimal changes in the frontal cortex functioning (Lam, Dickerson, Zoccola & Zaldivar, 2009; Luebbe, Elledge, Kiel & Stoppelbein, 2012). Importantly, however, HPA-axis dysregulation is not considered pathological per se, but can rather index a psychobiological vulnerability that increases risk for mental health and developmental problems (Davis, Glynn, Waffarn, & Sandman, 2011).
This study analyzes children’s internalizing and externalizing mental health symptoms as well as their social and cognitive developmental problems, as assessed by their parents at the age of 7-8 years. It also analyzes children’s saliva cortisol levels and diurnal patterns as an index of HPA-axis functioning at the age of 10-11 years.
We aim to provide understanding of the ways how early experiences influence later child development, by analyzing the long-term impact of pre- and postnatal parental mental health on children.