Leptin in bipolar disorder: A systematic review and meta-analysis

Area of Science:

• Psychiatry
• Endocrinology
• Immunology

Background:

• Bipolar disorder (BD) is linked to higher rates of obesity and inflammation.
• Leptin, an adipokine, stimulates the immune system and pro-inflammatory cytokine production.
• Alterations in peripheral leptin levels across mood states in BD require further investigation.

Purpose of the Study:

• To conduct a meta-analysis comparing leptin levels in individuals with BD across different mood states (mania, depression, euthymia) versus healthy controls.
• To investigate potential alterations in serum and plasma leptin levels in bipolar disorder.

Main Methods:

• A systematic literature search was performed for eligible peer-reviewed articles.
• A between-group meta-analysis was conducted using Hedges' adjusted g.
• Eleven studies with 1118 participants were included.

Main Results:

• No significant differences in serum and plasma leptin levels were found in individuals with BD compared to healthy controls during mania, depression, or euthymia.
• A stronger association between leptin levels and age was observed in euthymic BD patients compared to controls.
• Higher BMI in euthymic BD patients was associated with a greater difference in leptin levels compared to controls.

Conclusions:

• Leptin levels are not altered across the mood spectrum in bipolar disorder when compared to healthy individuals.
• The disproportionate increase in leptin with rising BMI in BD suggests a potential inflammatory role for white adipose tissue.
• Leptin levels show a disproportionate increase with age in individuals with bipolar disorder.