By Ellen Feldman, MD

Altru Health System, Grand Forks, ND

Dr. Feldman reports no financial relationships relevant to this field of study.

SUMMARY POINTS

  • Norwegian researchers followed more than 700 participants between 6 to 10 years of age to investigate the reciprocal relationship between physical activity, sedentary periods, and subsequent onset of symptoms of depression.
  • Electronic monitors tracked physical exertion; structured interviews measuring depression assessed number of depressive symptoms.
  • Higher levels of moderate to vigorous physical activity (MVPA) at 6 years of age correlated with less depressive symptoms at 8 years of age. Likewise, higher levels of MVPA at 8 years of age correlated with less depressive symptoms at 10 years of age.
  • Sedentary periods did not correlate with higher levels of depressive symptoms, and depressive symptoms did not correlate with changes in physical activity in subsequent years.

SYNOPSIS: This prospective study found moderate to vigorous physical activity in early childhood correlated with a decreased number of depressive symptoms in later years.

SOURCE: Zahl T, Steinsbekk S, Wichstrom L. Physical activity, sedentary behavior, and symptoms of major depression in middle childhood. Pediatrics 2017;139(2). pii: e20161711. doi: 10.1542/peds.2016-1711. Epub 2017 Jan 9.

“Lack of activity destroys the good condition of every human being, while movement and methodical physical exercise save it and preserve it.”
— Plato

Today, with more automation and less need for physical action or intervention, Plato’s words take on greater significance. The essential role exercise plays in maintaining and improving health is unquestionable and validated by numerous well-designed and constructed studies.1 However, few researchers have studied the role of exercise and movement in the physical and emotional well-being of young children. Recognizing this as a gap in the field, Zahl et al set out to study a community sample of children to answer several relevant questions regarding this age group and mental health.

Specifically, this group was interested in a prospective study looking at a community-based sample of young children and exploring a relationship between physical activity and symptoms of depression. Specifically, the intention was to characterize the relationship in a bidirectional manner to see if there was a correlation between depressive symptoms and time spent engaging in physical activity and/or if there was a correlation between physical activity and onset of depressive symptoms. Recognizing psychomotor retardation as a symptom of depression, an additional goal was to isolate any effect from sedentary activity on depression.

Older children and adolescents have been the subjects in similar studies regarding physical activity and depressive symptoms. A large investigation in 2012, and another more recent study in 2017, found evidence of a reciprocal link between these two factors (depressive symptoms and physical activity) in this older age group.2,3 There have been conflicting results regarding the intensity of effort or degree of physical activity that is correlated with decreased depressive symptoms.

The Trondheim Early Secure Study is a prospective, longitudinal investigation beginning with a cohort group of children born in 2003 and 2004.4 The subgroup of children for this study received invitation letters prior to routine 4-year old well-child visits. Permission to participate was obtained at the visits followed by data collection at age 6 years, age 8 years, and age 10 years (2009-2015.) In total, 799 children submitted usable data.

To identify degree of physical activity, children wore waistband accelerometers that recorded activity for seven consecutive days. Standardized measures permitted identification of sedentary activity level and moderate-vigorous activity level, both represented as hours per day for study purposes. Sleep hours were not included in the study.

Structured, age-appropriate interviews of the children and a corresponding parent interview noted the presence of any symptoms of major depressive disorder. Reported for data analysis were the number of symptoms of depression present, rather than a firm diagnosis. Comorbidity from other psychiatric disorders and body mass index (BMI) were considered as potential confounders. To control for comorbidity, assessments for symptoms of several other psychiatric disorders were collected. BMI was calculated for each participant and controlled for in final statistical analysis.

Hours per day of sedentary activity at each age level and of moderate-vigorous physical activity (MVPA) as well as number of depressive symptoms were the main variables studied. Both states of physical activity — MVPA and sedentary — were defined numerically on the accelerometers; these standardized measures were used for the investigation. To convey this level of activity in words, Zahl et al subjectively described MVPA as “… being active, getting sweaty, and even breathless ….”

Out of nine possible symptoms of depression, the mean number of symptoms noted ranged from 0.46 to 0.52. (See Table 1.)

Table 1: Accelerometer and Interview Results for Each Age Group

Age in years

Mean number symptoms of depression (SD)

MVPA
(hours/day)

Sedentary (hours/day)

Age 6

0.52 (0.73)

1.19

8.58

Age 8

0.46 (0.79)

1.18

9.22

Age 10

0.52 (0.90)

1.09

9.94

MVPA = moderate-vigorous physical activity

A flexible statistical modeling program (M plus)5 enabled analysis of multiple variables and examination of bidirectional relationships between these variables. For example, using this program, a correlation between MVPA and symptoms of depression was examined, looking at time spent in MVPA and mean number of depressive symptoms between the ages of 6 years to 8 years, and then looking backward between the ages of 8 years to 6 years. In this same manner, bidirectional analysis of sedentary behavior and depressive symptoms proceeded.

Positive findings: At 6 and 8 years of age, higher levels of MVPA predicted lower levels of depressive symptoms two years later. The effect was statistically significant but not large; a 0.20 decrease in number of symptoms of depression correlated with one hour more spent in MVPA. However, with a mean number of depressive symptoms for all age groups close to 0.50, a decrease by even this small amount could prove meaningful in prevention of progression to full-blown depressive disorders. Table 2 shows the statistical results.

Table 2: MVPA and Number of Depression Symptoms

 

Beta coefficient*

95% confidence interval

P value

Ages 6-8

-0.58

-0.95 to -0.21

0.001

Ages 8-10

-0.58

-1.03 to -0.03

0.002

Results from bidirectional analysis

MVPA = moderate-vigorous physical activity

* negative value indicates reciprocal relationship

Negative findings: There was no identified correlation between sedentary activity and symptoms of depression. Symptoms of depression at any age did not correlate with changes in levels of MVPA in later years. In other words, although higher levels of MVPA were associated with a decrease in depressive symptoms in subsequent years, higher levels of depressive symptoms did not correlate with any specific change in MVPA in future years.

COMMENTARY

Can young children develop depression? The existence of depression in the first decade of life and the validity of diagnosis at such a young age was once a question in the field. Backed by empirical studies documenting confirmed diagnosis of depression in children as young as 3 years of age, it is a question no longer.6

However, treatment is another matter. Unfortunately, there are only a few small, randomized, clinical trials looking at treatment interventions. Current best practice recommendations for intervention involve specific, age-adjusted psychotherapy and parental/guardian intervention. Although studies are limited in scope and numbers, the implications of untreated depression are significant; specific findings about the effect of depression on growth and development in young children has propelled the standard away from “watchful waiting” and toward active treatment and prevention.7

Until recently, preventive efforts in the field primarily have revolved around psychosocial interventions. Future studies looking at active intervention, such as inducing higher levels of activity in children to prevent development of future depressive symptoms (and potentially of depressive disorders), will be useful in further understanding if this study is looking at strictly correlation or if causation is significant.

The study results looking at natural higher levels of MVPA in young children and the effect on later development of depressive symptoms are not particularly robust at first glance, but they hold significant potential. Zahl et al identified only a limited number of depressive symptoms in young children, consistent with a known rate of depression among this age group — 1% of preschoolers and 2% of school-aged children.7 Given that the baseline numbers are tiny, a decline in this area (representing number of depressive symptoms) could be difficult to detect. That there exists a reciprocal correlation between MVPA and symptoms of depression at a young age may be the most significant finding, as opposed to the quantification of this relationship.

Zahl et al speculated that the relationship between MVPA and depression may be explained on several levels, including that a significant portion of the MVPA in children stemmed from engagement in sports. They wondered if increased self-esteem and socialization from sports activities is a potential guard against later development of depression. Other explanations considered include the possibility of a genetic link between an innate temperament geared toward movement and mood stability (an explanation proposed in a comment connected to the original study).8

Interestingly, Zahl et al did not find a correlation between longer periods of sedentary activity and depressive symptoms. However, there is no information regarding low levels of physical activity and depressive symptoms; thus, it is difficult to form any conclusions regarding intensity of physical activity. It is also important to note that limiting the physical activity measurements to just one week every two years may have limited the power of the study. There is no evidence that an accurate reflection of a child’s level of activity can be extrapolated from measures taken over this relatively brief period. Expanded activity measurements may help develop a more nuanced understanding of the relationship between all levels of activity and development of depressive symptoms.

Limits of this study include a lack of geographical diversity among subjects — certainly larger, multiethnic/geographic studies are necessary to formulate conclusions. Additionally, it is important to note that having symptoms of depression (measured by clinical interview in this study) is different from a firm diagnosis of depression. Future studies looking at these and other factors — including an extended time of investigation to determine the effect of early MVPA during adolescent years, for example — will be useful in developing a better understanding of the relationship between MVPA and development of depression.

We know from previous studies that depressive symptoms are a risk factor for a later diagnosis of major depressive disorder. We know that untreated depression tends to run a waxing and waning course throughout a lifetime and is associated with considerable disability and functional impairment. We also know that current treatment of depression in childhood has limited efficacy, and that there is little evidence for use of conventional antidepressants in this age group.6,7

The integrative provider aligns with patients to develop a comprehensive health and wellness plan. Informing parents of young children that early engagement in MVPA may help delay or prevent the development of depressive symptoms in offspring may add a new dimension to such a plan.

While being clear that this is preliminary information, recommending that parents look toward a more active lifestyle for their children has potential benefits, not only for the prevention of depression, but also for wellness and health in general. A side benefit: Some parents will engage in MVPA along with children, leading to a more active and potentially healthy lifestyle for the entire family.

REFERENCES

  1. Schuch FB, Vancampfort D, Richards J, et al. Exercise as a treatment for depression: A meta-analysis adjusting for publication bias. J Psychiatr Res 2016;77:42-51.
  2. Wiles NJ, Hasse AM, Lawlor DA, et al. Physical activity and depression in adolescents: Cross-sectional findings from the ALSPAC cohort. Soc Psychiatry Psychiatr Epidemiol 2012;47:1023-1033.
  3. Baldursdottir B, Valdimarsdottir HB, Krettek A, et al. Age-related differences in physical activity and depressive symptoms among 10-19-year-old adolescents: A population based study. Psychol Sport Exerc 2017;28:91e99.
  4. Steinsbekk S, Wichstrom L, Viddal KR, et al. The Trondheim Early Secure Study (TESS). Available at: https://www.researchgate.net/project/The-Trondheim-Early-Secure-Study-TESS. Accessed July 10, 2017.
  5. Mplus. Available at: https://www.statmodel.com/features.shtml. Accessed Aug. 10, 2017.
  6. Luby JL. Preschool depression: The importance of identification of depression early in development. Curr Dir Psychol Sci 2010;19:91-95.
  7. Luby JL. Treatment of anxiety and depression in the preschool period. J Am Acad Child Adolesc Psychiatry 2013;52:346-358.
  8. Zahl T, Steinsbekk S, Wichstrom L. Physical activity, sedentary behavior, and symptoms of major depression in middle childhood. Pediatrics Available at: http://pediatrics.aappublications.org/content/early/2017/01/05/peds.2016-1711.comments. Accessed July 15, 2017.