Molecular Biomarkers for Pediatric Depressive Disorders: A Narrative Review

The Relationship between Neurobiological Function and Inflammation in Depressed Children and Adolescents: A Scoping Review

INTRODUCTION

Neurobiological dysfunction is associated with depression in children and adolescents. While research in adult depression suggests that inflammation may underlie the association between depression and brain alterations, it is unclear if altered levels of inflammatory markers provoke neurobiological dysfunction in early-onset depression. The aim of this scoping review was to provide an overview of existing literature investigating the potential interaction between neurobiological function and inflammation in depressed children and adolescents.

METHODS

Systematic searches were conducted in six databases. Primary research studies that included measures of both neurobiological functioning and inflammation among children (≤18 years) with a diagnosis of depression were included.

RESULTS

Four studies (240 participants; mean age 16.0 ± 0.6 years, 62% female) meeting inclusion criteria were identified. Studies primarily examined the inflammatory markers interleukin 6, tumor necrosis factor alpha, C-reactive protein, and interleukin 1 beta. Exploratory whole brain imaging and analysis as well as region of interest approaches focused on the anterior cingulate cortex, basal ganglia, and white matter tracts were conducted. Most studies found correlations between neurobiological function and inflammatory markers; however, depressive symptoms were not observed to moderate these effects.

CONCLUSIONS

A small number of highly heterogeneous studies indicate that depression may not modulate the association between altered inflammation and neurobiological dysfunction in children and adolescents. Replication in larger samples using consistent methodological approaches (focus on specific inflammatory markers, examine certain brain areas) is needed to advance the knowledge of potential neuro-immune interactions early in the course of depression.

Impacts of inflammatory cytokines on depression: a cohort study

BACKGROUND

Inflammatory factors are associated with depression. We seek to investigate the correlation between inflammatory cytokines and prognosis of depression or suicidal ideation and behavior at 3 months in depression patients.

METHODS

Eighty-two depressed outpatients were recruited and treated as usual. Plasma cytokines were measured at baseline. Patients were followed up with Patient Health Questionnaire-9 and suicidal ideation and behavior according to the item 3 of Hamilton depression scale for 3 months.

RESULTS

Compared to the depression patients with low level of interleukin-1β, the high one had severe depressive symptoms at month 2 and 3 (B 0.92, P < 0.01; B 0.86, P = 0.02; respectively). The incidence of suicidal ideation or behavior was 18.3% at 3 months. Depression patients with high levels of tumor necrosis factor-α showed high risk of suicidal ideation and behavior than the low one (OR 2.16, 95% CI 1.00-4.65, P = 0.04).

CONCLUSIONS

High levels of interleukin-1β and tumor necrosis factor-α were predictive of middle-term severe depressive symptoms and suicidal ideation and behavior respectively.

Associations of n-3 polyunsaturated fatty acid status and intake with paediatric major depressive disorder in Swiss adolescents: A case-control study

BACKGROUND

Observational studies suggest a link between n-3 polyunsaturated fatty acid (PUFA) intake, n-3 PUFA status, and depression in adults, but studies in adolescents are scarce. This study aimed to determine associations of n-3 PUFA status and intake with paediatric major depressive disorder (pMDD) in Swiss adolescents.

METHODS

We conducted a matched case-control study in 95 adolescents diagnosed with pMDD and 95 healthy controls aged 13 to <18 years. We analysed red blood cell (RBC) fatty acid (FA) composition (% of total FA). n-3 PUFA intake was assessed using a focused food frequency questionnaire and depression severity was assessed by the Children's Depression Rating Scale-Revised (CDRS-R).

RESULTS

Mean RBC eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were lower in cases than controls (EPA: 0.41 ± 0.11 vs 0.46 ± 0.12, p < 0.001; DHA: 4.07 ± 1.04 vs 4.73 ± 1.04, p < 0.001). Subsequently, the mean RBC n-3 index was lower (4.51 ± 1.10 vs 5.20 ± 1.11, p < 0.001) and the n-6/n-3 PUFA ratio higher (5.51 ± 1.25 vs 4.96 ± 1.08, p < 0.001) in cases than controls. Adolescents with a higher n-3 index had lower odds for depression (OR = 0.49 [95% CI: 0.32-0.71]). In contrast, the n-6/n-3 PUFA ratio was associated with higher odds for depression (OR = 1.58 [95% CI: 1.14-2.25]). Intake of alpha-linolenic acid, EPA and DHA did not differ between cases and controls.

CONCLUSION

Our results suggest that a higher RBC n-3 PUFA status during adolescence is associated with a lower risk for pMDD, whereas a higher n-6/n-3 PUFA ratio is associated with a higher risk for pMDD. Differences in n-3 PUFA intake did not explain the observed differences in n-3 PUFA status.

Depression in Adolescence and Brain-Derived Neurotrophic Factor

The incidence of depression among adolescents has been rapidly increasing in recent years. Environmental and genetic factors have been identified as important risk factors for adolescent depression. However, the mechanisms underlying the development of adolescent depression that are triggered by these risk factors are not well understood. Clinical and preclinical studies have focused more on adult depression, and differences in depressive symptoms between adolescents and adults make it difficult to adequately diagnose and treat adolescent depression. Brain-derived neurotrophic factor (BDNF) is known to play a critical role in the pathophysiology of many psychiatric disorders, including depression. However, there are still few studies on adolescent depression. Therefore, in this review paper, the causes and treatment of adolescent depression and the function of BDNF are investigated.