Is depression a causative factor in metabolic syndrome

depression and Metabolic Syndrome

Is Depression a Causative Factor in Metabolic Syndrome

Metabolic syndrome refers to a condition that includes a number of symptoms that fall under two major categories. Metabolic Syndrome (MS) can be diagnosed by a number of methods, one of which involves obesity and waist circumference. Currently, the working definition proposed by the U.S. National Cholesterol Education Program (NCEP) Adult Treatment Panel III (ATP III) is, with some modifications, widely recommended and used (AHA, 2010). The NCEP definition stipulates that MS is diagnosable by the co-presence of at least three of five definitive factors: 1) abdominal obesity, or excess fat tissue in and around the abdomen; 2) elevated triglycerides; 3) hypertension, or elevated blood pressure; 4) low levels of high-density lipoprotein (HDL) or "good" cholesterol; and 5) insulin resistance, or elevated glucose levels (AHA, 2010; Toker et al., 2008, 661). Diagnosis of metabolic syndrome is associated with elevated risks for developing cardiovascular disease, other diseases associated with plaque buildups in the arterial walls (including peripheral vascular disease and stroke), and type-2 diabetes: all of which can be a primary cause of patient mortality (AHA, 2010; Toker et al., 2008, 661). Statistics indicate that metabolic syndrome is already disturbingly prevalent within the United States. Projections suggest that the disorder currently affects more than 50 million Americans (AHA, 2010), and perhaps as much as 24% of the entire population (Toker et al., 2008, 661).

Metabolic syndrome represents one of the most serious health risks in American society. Two of the most serious and most common co-morbidities in metabolic syndrome are heart disease and diabetes. The directions of causality between these factors are key points of dispute among researchers in this field. Major depression and its association with metabolic syndrome is one of these factors. Current literature agrees that an association exists between metabolic syndrome and depression, but the direction of causality is obscure. Depression is a common mental disorder that presents with depressed mood, loss of interest or pleasure, feelings of guilt or low self-worth, disturbed sleep or appetite, low energy, and poor concentration. These problems can become chronic or recurrent and lead to substantial impairments in an individual's ability to take care of his or her everyday responsibilities. At its worst, depression can lead to suicide, a tragic, fatal consequence associated with the loss of about 850-000 lives every year.

Depression is the leading cause of disability as measured by Years Living with Disability (YLDs) and the 4th leading contributor to the global burden of disease Disability Adjusted Life Years (DALYs) in 2000. By the year 2020, depression is projected to reach 2nd place of the ranking of DALYs calcuated for all ages and both sexes. Today, depression is already the 2nd cause of DALYs in the age category 15-44 years for both sexes combined.

Metabolic syndrome has become one of the most widely researched health problems in the United States. Treatment and other costs associated with metabolic syndrome and its co-morbid problems are easily in the billions. Depression is now one of the key mental illnesses in the U.S. As well. A multitude of information about metabolic syndrome is disseminated through television. The news and public service announcements has made metabolic syndrome and it co-morbidities common knowledge. Unfortunately, despite this barrage of information, the general population of Americans continue to suffer from diseases that are preventable with a few basic lifestyle changes.

The connection between diabetes and metabolic syndrome is well established. However, much of the literature considers depression to be a result of metabolic syndrome, and not the other way around. There is no main cause attributed to metabolic syndrome because it seems to be related to a number of causes. Some causes such as organic dysfunctions, damage to organs or disease cannot be avoided. However, many causes of metabolic syndrome are related to behaviors of the individual.

The topics of both depression and metabolic syndrome are well researched, with almost too much information to search through to make a proper assessment for the purpose of conducting a literature review. There is much information available from both credible academic resources and from sources that take a more speculative approach to the problem. For the purposes of this literature review, sources were selected that were representative of the key trends in research and conclusions in the area. Government authorities and organizations such as the NHLBI and AHA are also considered to the representative of research in this area.

A majority of the research found indicates that a connection does exist between primary depression and metabolic syndrome. These studies were conducted on a number of different age groups and categories of patients as well on the general public. Patient groups that have been studied include middle-aged adults of both sexes (Akbaraly, Kivimaki, & Brunner, et al. (2009), white African-Americans women (Goldbach, Bromberg, Matthews (2008), and the general population (Dunbar, Reddy, & Davis-Lameloise et al., 2008). Many more cohort groups can be found, but these were the key groups that were studied in the recent literature examined. Research into many of the other cohorts was from older literature and was not included in this literature review due to age.

The Whitehall II prospective cohort study by Akbaraly, Kivimaki, and Brunner, set out to examine whether metabolic syndrome was associated with the onset of depressive symptoms. The study included 5, 232 participants ranging in ages from 41 to 61. Assessment of metabolic syndrome was clearly defined according to criteria of the National Cholesterol Education Program (NCEP). The assessment of depressive symptoms utilized a 4-item depression subscale of the 30-item General Health Questionnaire (GHQ). Logistic regression was used to model the association between metabolic syndrome and each of its components at phase 3 and the onset of depressive symptoms between phases 3 and 5. After adjusting for potential cofounders, metabolic syndrome was associated with an increased risk of future depressive symptoms. Central obesity, high triglyceride levels and low HDL cholesterol levels predicted depressive symptoms. Findings concluded that depressive symptoms were more a consequence of the metabolic syndrome rather than a cause. The study's strength was its large sample size. Weakness of the study was that it measured depressive symptoms using a short scale, which is not a valid measure of a clinically recognized psychiatric disorder. Another weakness of the study was that participants were mainly white, which limited the external validity of the findings.

The aim of a stratified random sample cross-sectional survey by Dunbar, Reddy, Davis, Philpot…Janus, was to examine whether depression, anxiety, and psychological distress were associated with metabolic syndrome and its components. The hospital Anxiety and Depression Scale assessed depression and anxiety in 1,690 men and women between the ages of 25 -- 84. Psychological distress was assessed by the Kessler 10 measures. Statistical analysis was undertaken using SPSS version 14.0. Internal consistency was determined using Cranach's alpha. Pearson correlation coefficients were used to assess the intercorrelations between depression, anxiety and psychological distress. Multivariate analysis of covariance was used to test differences between individuals with the metabolic syndrome and indiviuals without the metabolic syndrome for psychological distress, anxiety, and depression. ANCOVA used to examine the association between depression and the five components of metabolic syndrome simultaneously. The studiy findings were that major depression is a significant predictor of the onset of metabolic syndrome.

In this study, women who were free of metabolic syndrome at the time of baseline measurement, and who had a lifetime major depression history or current major depressive episode at baseline were found to be significantly associated with the onset and presence of metabolic syndrome during the follow-up. Survival analysis showed that, in women who were free of metabolic syndrome at baseline, a lifetime major depression history or current major depressive episode at baseline were predictive of increased risk of developing the metabolic syndrome during follow-up. The key strengths of the study were its heterogeneity and its sample size. A key limitation of the study was its cross-sectional design, which does not allow for the demonstration of the existence of HPA axis activation and an inflammatory state in participants with central obesity. Establishment of this link requires both longitudinal investigations and further analysis of blood samples that would allow direct examination of the link between depression and metabolic syndrome.

A prospective cohort study by Goldbacher, Bromberger and Matthews examined the association of major depression and metabolic syndrome in white and African-American women. The study consisted of 281 white women and 148 African-American women. Structured clinical interview for the Diagnostic and Statistical Manual of Mental Disorders at baseline and seven annual follow-up evaluations were performed. Metabolic syndrome was measured at baseline and each follow-up evaluation based on National Cholesterol Education Program criteria. The study findings were that major depression is a significant predictor of the onset of the metabolic syndrome. Women who were free of metabolic syndrome at baseline, had a lifetime major depression history or current major depressive episode at baseline was significantly associated with the onset and presence of metabolic syndrome during the follow-up. Survival analysis showed that, in women who were free of metabolic syndrome at baseline, a lifetime major depression history or current major depressive episode at baseline predicted an increased risk of developing metabolic syndrome during follow-up. A key strength of the study was that it was the first to show that major depression predicts increased risk for developing metabolic syndrome in middle-aged women. One of the key limitations of the study was that it only evaluated the role of depression in middle-aged women and not in men. This limits the external validity of the study. In addition, the use of cross-sectional data, self-reports, or the measurement of depressive symptoms as opposed to clinical depression only provided indirect support for the link between depression and the risk of developing metabolic syndrome.

Although a majority of the research agrees that a clear connection exists between depression and metabolic syndrome, several sources disagree. Hildrum, Mykletun, Midthjell and associates (2008) are a key example of research that does not support the connection between depression and anxiety with metabolic syndrome. This study used a cross sectional study of participants aged 20-89. The sample consisted of 9,571 participants, representing an exceptionally large sample population. The study used HADS self-report questionnaires to measure depression and anxiety, and metabolic syndrome assessed according to the 2005 International Diabetes Federation criteria. All tests were administered to patients in a hospital setting. The results of the study demonstrated only a weak association between depression and metabolic syndrome. The study adjusted for the presence of cardiovascular disease and antidepressants. This study, reviewed by Hildrum and associates, represents one of the largest studies on the connection between depression and metabolic syndrome. The study appears to conflict an overwhelming number of studies that suggest that a connection does exist between depression and metabolic syndrome. However, it does not say that no connection exists, only that the connection is weak. In light of the current research, it is important to remember that every individual patient is indivudal and results may vary. Even if the study proves true for a small number of patients, it will be helpful for those patients that fall within that category.