Depression in late life often follows a chronic course with residual depressive and anxiety symptoms. Levels of omega-3 polyunsaturated fatty acids (PUFAs) have been found to be depleted in people with major depression in the acute stage. Additionally, lower omega-3 PUFA levels have been suggested to be associated with anxiety. The aim of this study was to investigate whether PUFAs levels (omega-3 or omega-6) are correlated with residual depressive or anxiety symptoms in older people with previous depression.

Participants aged 60years or over with previous major depression in remission were enrolled from outpatient psychiatric services of four hospitals. Participants with residual depressive symptoms were defined as the Hamilton Depression Rating Scale (HDRS) scores >5, and those with anxiety were defined as sum of scores for the two anxiety subscale of HDRS≧2. The levels of fatty acids in erythrocyte membranes and in plasma were measured separately by gas chromatography.

One hundred and thirty two older people with previous major depression (mean age of 68years, range 60-86years) were analyzed. Erythrocyte membrane linoleic acid levels had a curvilinear association with depressive symptoms and anxiety symptoms. Plasma linoleic acid levels were found to have a negative linear relationship with depressive symptoms. No significant associations were found between any omega-3 fatty acid level and depressive or anxiety symptoms.

Linoleic acid levels may be a possible biomarker for residual depression and anxiety in older people with previous depression. Possible clinical applications need further investigation.