Plasma Neuropeptide Y Levels in Medication Naive Adolescents with Major Depressive Disorder

Correlates of suicidality in young people with depressive disorders: A systematic review

OBJECTIVE

Depression is one of the most prevalent and disabling mental health conditions among young people worldwide. The health and economic burdens associated with depressive illness are substantial. Suicide and depression are closely intertwined, yet a diagnosis of depression itself lacks predictive specificity for suicidal behaviour. To better inform suicide prevention and early intervention strategies for young people, improved identification of modifiable intervention targets is needed. The objective of this review was to identify clinical, psychosocial and biological correlates of suicidality in young people diagnosed with a broad range of unipolar and bipolar depressive disorders.

METHOD

Systematic searches were conducted across MEDLINE, Embase and PsycINFO to identify studies of young people aged 15-25 years diagnosed with unipolar or bipolar depressive disorders. An assessment of suicidality was required for inclusion. Reporting followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 and Synthesis Without Meta-analysis guidelines.

RESULTS

We integrated findings from 71 studies including approximately 24,670 young people with clinically diagnosed depression. We identified 26 clinical, psychosocial and biological correlates of suicidality. Depression characteristics (type and severity), psychiatric comorbidity (particularly anxiety and substance use disorders) and neurological characteristics emerged as having the most evidence for being associated with suicidal outcomes. Our ability to pool data and conduct meaningful quantitative synthesis was hampered by substantial heterogeneity across studies and incomplete reporting; thus, meta-analysis was not possible.

CONCLUSION

Findings of this review reinforce the notion that suicidality is a complex phenomenon arising from the interplay of multiple contributing factors. Our findings question the utility of considering a diagnosis of depression as a specific risk factor for suicidality in young people. Suicidality itself is transdiagnostic; adoption of a transdiagnostic approach to investigating its aetiology and treatment is perhaps warranted. Future research investigating specific symptoms, or symptom networks, might help to further our understanding of suicidality among young people experiencing mental illness.

Neuropeptide Y in PTSD, MDD, and chronic stress: A systematic review and meta-analysis

Previous studies have suggested that neuropeptide Y (NPY) levels may be altered in patients with major depressive disorder (MDD), post-traumatic stress disorder (PTSD) and chronic stress. We investigated, through systematic review and meta-analysis, whether the mean levels of NPY are significantly different in patients with MDD, PTSD or chronic stress, compared to controls. The main outcome was the pooled standardized mean difference (SMD) with 95% confidence intervals between cases and controls, using the random-effects model. Heterogeneity and publication bias were evaluated. Thirty-five studies met eligibility criteria. Meta-regression determined that medication and sex could explain 27% of the between-study variance. Females and participants currently prescribed psychotropic medications had significantly higher levels of NPY. NPY levels were significantly lower in plasma and cerebrospinal fluid (CSF) in PTSD patients versus controls. Patients with MDD had significantly lower levels of NPY in plasma compared to controls, but not in the CSF. The magnitudes of the decrease in plasma NPY levels were not significantly different between PTSD and MDD. However, chronic stress patients had significantly higher plasma NPY levels compared to controls, PTSD or MDD. Our findings may imply a shared role of NPY in trauma and depression: nevertheless, it is not clear that the association is specific to these disorders. Psychotropic medications may help restore NPY levels. Further controlled studies are needed to better delineate the contribution of confounding variables such as type of depression, body mass index, appetite or sleep architecture.