PT  - JOURNAL ARTICLE
AU  - T Kendrick
AU  - N Dunn
AU  - S Robinson
AU  - A Oestmann
AU  - K Godfrey
AU  - C Cooper
AU  - H Inskip
AU  - the Southampton Women’s Survey Study Group
TI  - A longitudinal study of blood folate levels and depressive symptoms among young women in the Southampton Women’s Survey
AID  - 10.1136/jech.2007.069765
DP  - 2008 Nov 01
TA  - Journal of Epidemiology and Community Health
PG  - 966--972
VI  - 62
IP  - 11
4099  - http://jech.bmj.com/content/62/11/966.short
4100  - http://jech.bmj.com/content/62/11/966.full
SO  - J Epidemiol Community Health2008 Nov 01; 62
AB  - Background: Lower blood folate levels have been associated with depression in cross-sectional surveys, but no studies have examined the relationship prospectively to determine whether the relationship is causal. A follow-up study was designed to examine whether lower blood folate levels predict incident depressive symptoms.Method: Women aged 20–34 years registered in general practices in Southampton, UK, were asked to participate. Baseline assessment included the general health questionnaire (GHQ-12) measure of anxiety and depression, and socioeconomic factors, diet, smoking and alcohol intake. Two years later, participants’ general practice (GP) records were examined for evidence of incident symptoms of depression.Results: At baseline, 5051 women completed the GHQ-12 and had red cell folate levels measured, of whom 1588 (31.4%) scored above the threshold for case level symptoms of anxiety and depression on the GHQ-12. Two years later, GP records for 3996 (79.1%) were examined, but 1264 with baseline evidence of depression were excluded from follow-up analysis. Incident depressive symptoms were recorded for 307 (11.2%) of the remaining 2732. Lower red cell folate levels were associated with caseness on the GHQ-12 (adjusted prevalence ratio 0.99 per 100 nmol/l red cell folate, 95% CI 0.98 to 1.00). No relationship was found between red cell folate levels and incident depressive symptoms over 2 years (adjusted hazard ratio 1.00, 95% CI 0.97 to 1.03).Conclusions: Low folate levels were not associated with subsequent depressive symptoms. This suggests that lower blood folate levels may be a consequence rather than a cause of depressive symptoms.