Smaller hippocampus volume is associated with short variant of 5-HTTLPR polymorphism in medication-free major depressive disorder patients.
OBJECTIVE
Serotonin is known for its importance in the pathophysiology of major depressive disorder. Although the hippocampus is one of the key regions in which neurogenesis occurs, and serotonin plays an important role in neurogenesis, results of studies that investigate effect of the 5-HTTLPR polymorphism on hippocampal volumes in major depressive disorder are inconclusive.


METHODS
We looked for a relationship between the 5-HTTLPR polymorphism and hippocampal volumes in 44 depressed patients (mean age ± SD 33.6 ± 9.5 years) and 43 healthy controls (30.4 ± 6.7 years). Region of interest analysis was conducted on the images acquired via MRI.


RESULTS
Although hippocampal volumes were similar in healthy and patient groups, there was a significant interaction between genotype and diagnosis on hippocampus volumes. Post-hoc ANCOVA showed that hippocampal volumes of S/S homozygous depressed patients were smaller compared to healthy controls in both hemispheres.


CONCLUSIONS
The 5-HTTLPR polymorphism has an effect on hippocampal volumes of depressed patients, which is apparent only in S/S genotype. It seems that decreased neurogenesis by effects of reduced serotoninergic transmission may be responsible for smaller hippocampal volumes observed in S/S homozygous depressed patients.
Department of Psychiatry, Affective Disorders Unit, Ege University School of Medicine, Izmir, Turkey.
M Cagdas
MC
Eker
Omer
O
Kitis
Hamza
H
Okur
Ozlem Donat
OD
Eker
Erol
E
Ozan
Serhan
S
Isikli
Nurten
N
Akarsu
Ali Saffet
AS
Gonul
D000328:Adult; D000483:Alleles; D003865:Major Depressive Disorder / Q000235:genetics* / Q000473:pathology*; D005260:Female; D005838:Genotype; D006624:Hippocampus / Q000473:pathology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D011110:Polymorphism, Genetic; D011569:Psychiatric Status Rating Scales; D050486:Serotonin Plasma Membrane Transport Proteins / Q000235:genetics*
C493230:SLC6A4 protein, human; D050486:Serotonin Plasma Membrane Transport Proteins