Depression is a serious medical disorder characterized by a pervasive and persistent low mood that is accompanied by low self-esteem and by a loss of interest or pleasure in normally enjoyable activities. Now a new study published in the European Journal of Preventive Cardiology links depression as a risk for coronary heart disease (CHD).
Coronary heart disease refers to the narrowing of the small blood vessels that supply blood and oxygen to the heart. The medical condition is the leading cause of death for men and women in the United States. Chest pain or discomfort are the most common symptoms of CHD.
In the present study, researchers led Dr. Eric Brunner of the Department of Epidemiology and Public Health at University College London in the United Kingdom investigated the associations of depressive disorder with coronary heart disease and stroke. Previous studies have produced mixed results.
One possible reason for the mixed results is reverse causation, which refers to hypothetical phenomena or processes that reverse causality, allowing an effect to occur before its cause. Write the researchers, “With repeated exposure measurements over a long period of adult life, causal inference would be strengthened if (a) reverse causation was excluded as an explanation for the link between depressive disorder and vascular events, and (b) a dose–response effect was evident.”
To further explore the associations between depression and CHD, the researchers analyzed data from 10,308 civil servants in the UK who took part in the Whitehall II study. The participants completed a 30-item General Health Questionnaire at the beginning of the study. Follow-ups were conducted every two to three years over a period of up to 20 years.
According to the study, there is no causal relationship between depression and stroke. A link between depressive symptoms and stroke appeared only after a short follow-up period, indicating a reverse causation effect. Explains Dr. Brunner, “In other words, depressive symptoms may be a sign of imminent stroke, but are not causally related.”
The researchers also discovered no increased risk for coronary heart disease during one or two of the questionnaire assessments.
However, the risk for CHD increased by 100 percent in the participants who reported depressive symptoms at three or four of the assessments. Thus, the researchers conclude that there evidence of a dose–response effect of depressive symptoms on the risk of coronary heart disease.
Comments Dr. Brunner on the findings:
“European prevention guidelines refer to depression as a coronary risk factor, and in our study repeated episodes of depressive symptoms accounted for 10% of all CHD events in the study population.
“However, this figure relies on the strong assumption of a direct causal mechanism. Whether or not the association is causal, supporting individuals to recover from chronic or repeated episodes of depression has merit, particularly if the individual is then better able to reduce any vascular risk, for example by quitting smoking.”
One explanation for the different effects of depression on CHD and stroke is blood pressure. Depressive symptoms have been linked with low blood pressure. Blood pressure is particularly important for stroke risk but only one of several risk factors for coronary heart disease.
Another recent study concluded that depression is a risk factor for diabetes.
References
Depression is ‘a causal risk of coronary heart disease’: http://www.medicalnewstoday.com/articles/272149.php
Depressive disorder, coronary heart disease, and stroke: dose–response and reverse causation effects in the Whitehall II cohort study: http://www.ncbi.nlm.nih.gov/pubmed/24491401
Symptoms of depression causally linked to risk of coronary heart disease in UK Whitehall study: http://www.escardio.org/about/press/press-releases/pr-14/Pages/depression-causally-linked-heart-disease.aspx?hit=dontmiss
Image Credits
Depressed Man: http://www.freeimages.com/photo/1313532
