Childhood cognitive ability and its relationship with anxiety and depression in adolescence

Abstract

Background

Childhood cognitive ability may have protective effects against internalizing symptoms in adolescence, although this may depend on the time of symptom assessment and child gender. Also, the effects of childhood stressors on adolescent internalizing symptoms may be moderated by childhood cognitive ability.

Methods

The sample included 4405 individuals from the Canadian National Longitudinal Study of Children and Youth (NLSCY). Between ages 4–5 and 10–11, children completed a test of verbal ability and scholastic aptitude and a series of mathematics computation tests. Internalizing symptoms were assessed via self-reports at ages 12–13 and 14–15.

Results

Greater cognitive ability was generally associated with decreased odds of internalizing symptoms at age 12–13. However, greater cognitive ability generally increased, or had no effect on, the odds of internalizing symptoms at age 14–15. Some of the effects of childhood cognitive ability varied with child gender. Also, childhood cognitive ability attenuated the effects of family dysfunction and chronic illness throughout childhood on subsequent internalizing symptoms.

Limitations

These data are largely subject to some degree of reporting bias, the tests of cognitive ability are limited and may not represent overall cognitive ability, and there may be intermediary variables that account for the relationship between childhood cognitive ability and adolescent internalizing symptoms.

Conclusion

Results suggest that programs attempting to increase early cognitive skills may be particularly beneficial for girls. Also, an increased focus on cognitive skills may attenuate the negative effects of some stressors on subsequent anxious and depressive symptoms, regardless of child gender.

Introduction

Feelings of anxiety and depression, or internalizing symptoms, are among the most common psychiatric problems experienced by adolescents (Costello et al., 2005). Although most individuals will not meet diagnostic criteria for clinical anxiety and mood disorders, the presence of internalizing symptoms have nevertheless been shown to increase the risk for subsequent psychiatric disorders (Pine et al., 1999, Ashford et al., 2008). Moreover, anxious and depressive disorders have been shown to represent a significant economic burden to society (Greenberg et al., 1999, Greenberg et al., 2003). The identification of risk and protective factors for internalizing symptoms is therefore an important first step in the prevention of psychiatric disorders in young people.

One possible protective factor against the development of internalizing symptoms is childhood cognitive ability, a concept synonymous with general intelligence (Ek et al., 2013, Woodward et al., 2012, Bruni et al., 2012, Trippas et al., 2013) and involving skills such as problem solving, memory, and verbal ability (Vernon, 1971, Ashton et al., 1979, Defries et al., 1979, Sass et al., 1995). Evidence suggests that child and youth internalizing symptoms are associated with a deficit in cognitive functioning. For example, children with social phobia have been shown to have certain types of memory deficit (Vasa et al., 2007), and may also have a greater amount of neurodevelopmental delay (Kristensen and Torgersen, 2008) as compared to other children. Children with greater internalizing symptoms also tend to have more difficulty with various cognitive tasks such as those involving problem solving (Emerson et al., 2005). Moreover, lower IQ has been associated with greater depression, especially in young adult men (Zammit et al., 2004, Rabbitt et al., 1995), and children with anxiety disorders tend to have lower IQ scores than non-anxious children (Hodges and Plow, 1990, Davis et al., 2008, Kristensen and Torgersen, 2008).

These findings suggest that children experiencing higher levels of anxiety and depression should have more difficulty in academic settings. There is some evidence of an educational gradient in depression, possibly resulting from differences in cognitive ability (Lee, 2011). Indeed, academic performance has been negatively associated with symptoms of anxiety and depression in children (Cole, 1991, Lin et al., 2011, Rapport et al., 2001). In addition, both academic competence in adolescence and high school completion are negatively associated with symptoms of anxiety and depression in young adulthood (Masten et al., 2005, Topitzes et al., 2009), and early academic achievement lowers the odds of persistently high levels of depression throughout adolescence and young adulthood (Stoolmiller et al., 2005). In contrast, other research suggests that educational attainment in early adulthood is associated with greater internalizing symptoms at age 53 (Hatch et al., 2007).

Most of the research examining the associations between markers of cognitive ability and internalizing symptoms to date has been cross-sectional, and thus the direction of effect in these associations, as well as the role of early cognitive ability on later internalizing symptoms, remains largely unexamined. Nevertheless, a small number of longitudinal studies suggest that cognitive ability early in life can have a significant effect on the later development of internalizing symptoms. For example, higher academic achievement in grade 1 has been shown to predict lower internalizing symptoms 2 years later (Burt and Roisman, 2010). Also, there is evidence that low IQ in adolescence increases the risk of depression in middle age (Der et al., 2009, Franz et al., 2011) and low IQ in childhood increases the risk of internalizing symptoms in adulthood (Koenen et al., 2009).

However, the role of intelligence in the development of subsequent internalizing symptoms may depend on a number of factors, including the age at which these symptoms are assessed and participant gender. For instance, one study found that IQ at age 8 was inversely related to depressive symptoms at age 11, but positively related to these symptoms at ages 13 and 14 (Glaser et al., 2011), while another study found that childhood cognitive ability was only related to fewer adult internalizing symptoms for women (Hatch et al., 2007).

Although childhood cognitive ability may be a protective factor against subsequent internalizing symptoms, it is not clear why this would be the case. One possibility is that children with greater cognitive ability are better equipped to cope with various sources of stress that may be important in the development and maintenance of internalizing symptoms. That is, cognitive ability may buffer children and youth against the effects of stress on anxiety and depression. However, support for this idea is mixed. One study found that stressful life events and depression in adulthood were positively associated only among those participants with lower cognitive ability at age 15 (Van Os and Jones, 1999). Another study of high-risk adolescents also failed to find evidence that greater intelligence gives adolescents an advantage in coping with stress (Luthar, 1991).

The first objective of the current study was to examine the relationship between cognitive ability in childhood and internalizing symptoms in adolescence. We hypothesized that cognitive ability in childhood would generally be inversely associated with internalizing symptoms in adolescence. However, we acknowledged the possibility that the effect of cognitive ability depends on the time of assessment of internalizing symptoms, with more protective effects in younger adolescents than older adolescents. The second objective was to examine gender differences in the effect of childhood cognitive ability on adolescent internalizing symptoms. We hypothesized that girls may benefit more from greater cognitive ability than boys. The third objective was to examine the potentially moderating role of childhood cognitive ability on the relationships between childhood stressors and internalizing symptoms in adolescence. Cognitive ability was expected to attenuate the influence of childhood stressors on adolescent internalizing symptoms.