Inverse relationship between leptin increase and improvement in depressive symptoms in anorexia nervosa

OBJECTIVES: Anorexia nervosa (AN) often presents with comorbid depressive symptoms and is characterized by low levels of neuroimmunomodulatory hormone - leptin. Treatment-induced weight gain tends to normalize those variables. The aim of the study was the longitudinal assessment of the relationship between leptin levels and depressive symptoms in patients with AN, since previous cross-sectional studies in different populations brought conflicting results. METHODS: Thirty AN inpatients were assessed twice - at admission and after mean body mass index (BMI) increase of 3.2 kg/m(2). Physical parameters were measured, blood samples for leptin levels drawn and depression evaluated with both clinician - (Hamilton Depression Rating Scale - HDRS) and self -(Beck Depression Inventory - BDI) rated scales at the same morning. Correlation coefficients between changes in assessed variables, and linear regression for changes in depression scores were calculated. RESULTS: BMI and leptin levels showed significant increase after treatment, respectively 14.45 +/- 0.90 vs. 17.61 +/- 0.87 and 1.87 +/- 1.14 vs. 7.47 +/- 4.65, whereas severity of depressive symptoms measured with BDI and HDRS was significantly reduced: 18.69 +/- 12.65 vs. 11.62 +/- 11.59; 12.76 +/- 6.90 vs. 5.66 +/- 4.91, respectively. In linear regression analysis decrease of the clinician-rated depression score (HDRS) was directly associated with decrease in the self-assessed depressive symptoms (BDI) (standardized Beta=0.45; t=2.60; p<0.05) and inversely related to the increase in leptin level (standardized Beta=-0.33; t=-2.08; p<0.05). CONCLUSIONS: These results may suggest, that increase in leptin levels during weight recovery in patients with AN is associated with objectively measured depressive symptoms. Longitudinal studies in other populations are warranted to establish whether this relationship is valid across the weight spectrum.