Department of Psychiatry, Taipei Medical College-Affiliated Wan Fang Hospital, No. 111, Hsing-Lung Road Sec. 3, Taipei 116, Taiwan
Graduate Institute of Nutrition and Health Science, Taipei Medical College, Taipei, Taiwan
We read with interest the excellent large-scale prospective study reported by Partonen et al (1999). They found that low serum total cholesterol appears to be associated with low mood and suicide. However, others have reported conflicting results (McCallum et al, 1994). Weidner et al (1992) found that patients on a cholesterol-lowering diet were associated with reductions in depression if they were instructed to increase fish consumption. This implied that differences in the composition of polyunsaturated fatty acids (PUFAs) might explain the conflicting finding. The PUFAs are classified into two main groups: omega-3 (or n-3) of which the parent essential fatty acid is alpha-linolenic acid (C18:3n-3), and n-6, of which the parent essential acid is linoleic acid (C18: 2n-6). Maes et al (1999) found that major depression is associated with: significantly decreased total n-3 fatty acids; increased monounsaturated fatty acids and C22: 5n3 proportions and increased C20:4n6/C20:5n3 and C22:5n6/C22:6n3 ratios; lower C22:4n6, C20:5n3 and C22:5n3 fractions in phospholipids; lower C18:3n3, C20:5n3 and total n3 fatty acids, and higher C20:4n6/C20:5n3 and n6/n3 ratios in cholesteryl esters; and lower serum concentrations of phospholipids and cholesteryl esters. These findings are consistent and have shown well-established positive correlation between depression and coronary artery disease. Many studies have documented evidence of hypothalamic-pituitary-adrenocortical axis hyperactivity within medication-free patients with major depression, including hypercortisolaemia (Raadsheer et al, 1994). Hypercortisolaemia can induce hypercholesterolaemia, hypertriglyceridaemia and hypertension. These are well known to be predisposing factors of cardiovascular disease. If low serum cholesterol concentrations were linked to increased depression, it would be difficult to interpret the correlation between depression and coronary artery disease. The relationship between cholesterol and depression may not be specific enough.
REFERENCES
Maes, M., Christophe, A., Delanghe, J., et al (1999) Lowered omega-3 polyunsaturated fatty acids in serum phospholipids and cholesteryl esters of depressed patients. Psychiatry Research, 85, 275-291.[CrossRef][Medline]
McCallum, J., Simons, L., Simons, J., et al (1994) Low serum cholesterol is not associated with depression in the elderly: data from an Australian community study. Australian and New Zealand Journal of Medicine, 24, 561-564.[Medline]
Partonen, T., Haukka, J., Virtamo, J., et al (1999) Association of low serum total cholesterol with major depression and suicide. British Journal of Psychiatry, 175, 259-262.[Abstract]
Raadsheer, F. C., Hoogendijk, W. J. G., Stam, F. C., et al (1994) Increased numbers of corticotropin-releasing hormone expressing neurons in the hypothalamic paraventricular nucleus of depressed patients. Neuroendocrinology, 60, 436-444.[Medline]
Weidner, G., Connor, S. L., Hollis, J. F., et al (1992) Improvements in hostility and depression in relation to dietary change and cholesterol lowering. Annals of Internal Medicine, 117, 820-823.[Medline]
National Public Health Institute, Department of Mental Health and National Research, Mannerheimintie 166, FIN-00300, Helsinki, Finland
National Public Health Institute, Department of Nutrition, Helsinki, Finland
National Public Health Institute, Department of Mental Health and Alcohol Research, Helsinki, Finland
We analysed data from the ATBC Cancer Prevention Study, which was a primary prevention trial to test whether alpha-tocopherol and beta-carotene supplements would reduce the incidence of lung and other cancers (ATBC Cancer Prevention Study Group, 1994). Smokers were recruited from the total population of elderly men and assessed for eligibility. A previous diagnosis of cancer, current severe angina with exertion, chronic renal insufficiency, cirrhosis of the liver, alcohol dependence, or a disorder limiting participation in the long-term trial were grounds for exclusion.
We concluded that low serum total cholesterol appeared to be associated with low mood. We also found that low serum total cholesterol predicted, after adjusting for risk factors, the occurrence of conditions indicative of poor outcome, such as hospitalisation owing to major depressive disorder and death from suicide. Findings were similar for violent deaths exclusive of suicide. Trial supplementation had no effect on the main outcome measures, as we reported in the original paper, nor did the antioxidant supplementation modify the effect of serum total cholesterol on suicide.
Tanskanen et al (above) report in their letter that the risk of suicide was increased with higher serum total cholesterol levels in random samples of Finnish smokers. We do not have any obvious explanation for these conflicting findings, but study populations were rather dissimilar. Their subjects (aged 25-64 years) were mainly from eastern Finland, whereas our subjects (aged 50-69 years) were from south-western Finland. The results of other cohort studies investigating the association of serum total cholesterol levels with death from suicide have been inconsistent, since there has been no association or the association has been inverse in previous studies. Tanskanen et al, as well as Su et al (above), raise the possibility of dietary fatty acids affecting the occurrence of depressive disorder, which in turn is one of the strongest risk factors for suicide. Our aim is to analyse, in subsequent studies, the relationships between various dietary factors (fats, carbohydrates, and amino acids), depressed mood and suicide risk.
REFERENCES
ATBC Cancer Prevention Study Group (1994) The alpha-tocopherol, beta-carotene lung cancer prevention study: design, methods, participant characteristics, and compliance. Annals of Epidemiology, 4, 1-10.[Medline]