Modification by two genes of associations between general somatic health and incident depressive syndrome in older people.
OBJECTIVE
To investigate the modifying effects of two candidate genes (serotonin transporter gene linked promoter region (5-HTTLPR) and methylenetetrahydrofolate reductase (MTHFR) C677T polymorphisms) on the associations between general somatic morbidity and incidence of depression in an East Asian population with high frequencies of potential risk alleles.


METHODS
With a 2-year prospective study of a community sample (N = 521) of older people (aged 65+), information on baseline number of health complaints, diagnosis of moderate/severe depressive syndrome (Geriatric Mental State), and genotypes for 5-HTTLPR and MTHFR C677T polymorphisms were ascertained. Interactions between somatic morbidity and the two genotypes were investigated for incident depression.


RESULTS
Incident depression was present in 63 (12%) and was associated with worse somatic health. Significant interactions between number of somatic complaints and both genotypes were observed. For the 5-HTTLPR genotypes, the association between the number of somatic disorders and depression was significant in s/s homozygotes (chi2 = 8.80 (1 df), p = .003) but not in heterozygotes (chi2 = 0.23, p = .634) or l/l homozygotes (chi2 = 0.04, p = .840). For the MTHFR genotypes, the association between the number of somatic disorders and depression was significant in T/T homozygotes (chi2 = 4.97, p = .026) but not in C/T heterozygotes (chi2 = 1.24, p = .265) or C/C homozygotes (chi2 = 1.04, p = .307).


CONCLUSIONS
These findings suggest that associations between general somatic morbidity and late-life depression are modified by at least two genes, and that elders with particular genotypes are at greater risk for onset of depression in the presence of somatic ill health.
Kim
Jae-Min
JM
Department of Psychiatry and Depression Clinical Research Center, Chonnam National University Medical School, Kwangju, Republic of Korea.
Stewart
Robert
R
Kim
Sung-Wan
SW
Yang
Su-Jin
SJ
Shin
Il-Seon
IS
Yoon
Jin-Sang
JS
D000368:Aged; D002908:Chronic Disease; D017931:DNA Primers / Q000235:genetics; D003866:Depressive Disorder / Q000453:epidemiology* / Q000235:genetics*; D005260:Female; D005492:Folic Acid / Q000031:analogs & derivatives* / Q000235:genetics; D005838:Genotype; D006304:Health Status; D006801:Humans; D008297:Male; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic / Q000235:genetics*; D011446:Prospective Studies; D050486:Serotonin Plasma Membrane Transport Proteins / Q000235:genetics*; D012720:Severity of Illness Index; D013001:Somatoform Disorders / Q000175:diagnosis / Q000453:epidemiology* / Q000235:genetics*; D013577:Syndrome
D017931:DNA Primers; C493230:SLC6A4 protein, human; D050486:Serotonin Plasma Membrane Transport Proteins; C032418:5,11-methenyltetrahydrohomofolate; D005492:Folic Acid