by Randy A. Sansone, MD, and Lori A. Sansone, MD

Dr. R. Sansone is a professor in the Departments of Psychiatry and Internal Medicine at Wright State University School of Medicine in Dayton, Ohio, and Director of Psychiatry Education at Kettering Medical Center in Kettering, Ohio; Dr. L. Sansone is a family medicine physician in practice (government service) and Medical Director, Primary Care Clinic at Wright-Patterson Air Force Base. The views and opinions expressed in this column are those of the authors and do not reflect the official policy or the position of the United States Air Force, Department of Defense, or US government.


Introduction

A number of investigators have found a possible relationship between low serum cholesterol levels and mood disorders. In addition, low serum cholesterol levels have been associated with suicidal ideation and suicide attempts. While the pathophysiology of this association remains unknown, some researchers have postulated that there may be a relationship between altered lipid metabolism and changes in serotonin functioning. In addition, some researchers have found that the pharmacological treatment of depression results in increased serum cholesterol levels. While controversies and inconsistencies characterize this area of study, it appears reasonable to conclude the following: (a) alterations in lipid metabolism may be one of several risk factors for the subsequent development of depression and/or suicidal ideation/suicide attempts (i.e., a non-specific contributory variable) and/or (b) low serum cholesterol levels are an inconsistent but possible biological marker for the manifestation of these phenomena in some individuals.[1]

Low Cholesterol and Depression

A number of studies in various types of populations have found an association between low serum cholesterol levels and depressive symptoms and/or mood disorders.

General population studies. In a Finnish community sample of nearly 30,000 participants, investigators found that low serum cholesterol levels were associated with depressed mood and a heightened risk of hospitalization for depression.[2]

Outpatient samples. In addition to general population studies, the relationship between low serum cholesterol levels and depression has been explored in outpatient samples. For example, in an Irish study of primary care patients, Rafter found that participants with low serum cholesterol levels scored significantly higher on depression assessments.[3]

Inpatient samples. A relationship between low serum cholesterol levels and depressed mood has also been examined among various types of psychiatric inpatient samples. For example, in an Italian study, Borgherini and colleagues found that lower serum cholesterol levels correlated with higher scores on the depression assessment that was used in this study.[4] In a US study, Ghaemi and colleagues examined consecutive admissions to an affective disorders unit and found, compared with the bipolar subsample, lower cholesterol levels among those with unipolar depression.5 Glueck and colleagues examined hospitalized patients with affective disorders and, in comparison with controls, found a relationship between low serum cholesterol levels and affective disorders.[6] These findings have been replicated in other studies, as well.[7–9]

Cholesterol and depression in special populations. In addition to the association between low serum cholesterol levels and depressive symptoms/mood disorders in community and general patient samples, investigators have examined this relationship in somewhat unique types of populations. For example, Pjrek and colleagues confirmed this relationship in a controlled study of patients with seasonal affective disorder.[10] Dimopoulos and colleagues substantiated this relationship in a sample of elderly Greek patients.[11] Their findings among elderly patients were echoed in a sample of Finnish males[12] as well as a US sample of patients over the age of 70 years.[13] A relationship between low serum cholesterol and depressive symptoms has also been found among women during the post-partum period.[14–16]

Studies with negative findings. While a substantial number of studies indicate an association between low serum cholesterol levels and depressive symptoms and diagnoses, not all studies have found support for such a relationship. For example, in a nonclinical sample of Japanese males, investigators found that higher serum cholesterol levels were associated with depression.[17] Negative findings have been reported in several other clinical studies of depressed individuals as well.[18–25] To augment the preceding findings, among a large retrospective sample of patients suffering from affective psychoses, Fritze and colleagues found no association between low serum cholesterol levels and depressive symptoms.[26] Findings have also been negative in several studies of post-partum women.[27,28]

Low Cholesterol and Suicidal Ideation/Suicide Attempts/parasuicide

Cholesterol and suicidal ideation. In addition to studies on the relationship between cholesterol and depressive symptoms/disorders, investigators have also examined the relationship between low serum cholesterol levels and suicidal ideation. For example, in a controlled study from South Korea, Kim and Myint examined depressed patients admitted to an emergency department and developed subsamples according to the presence or not of suicidal ideation.[29] Compared to those without such ideation, those with suicidal ideation evidenced lower serum cholesterol levels. These findings were replicated in a Polish study by Rabe-Jablonska and Poprawska, in which low serum cholesterol levels statistically correlated with suicidal ideation.[30]

Cholesterol and suicide attempts. In addition to suicidal ideation, low serum cholesterol levels have been associated with bonafide suicide attempts. For example, in a controlled study from the UK, Kunugi and colleagues examined patients who were admitted from the emergency department following a suicide attempt; compared with non-attempting psychiatric inpatients and normal controls, those with suicide attempts evidenced lower serum cholesterol levels.[31] Sarchiapone and colleagues examined patients who were admitted to hospital following an intentional overdose.[32] Compared with controls, the cohort of patients’ status-post overdose had significantly lower serum cholesterol levels. In an Israeli sample, Modai and colleagues found that compared with non-suicidal depressed patients, suicide attempters evidenced significantly lower serum cholesterol levels.[33]

In keeping with these data, researchers from New Zealand examined the relationship between low serum cholesterol levels and the degree of the suicidal process. Using three levels of status (i.e., no suicidal thoughts, suicidal thoughts, suicide attempt), Sullivan and colleagues found that there was a significant association between lower serum cholesterol levels and increasing degrees of suicidal experience.[34]

Finally, Garland and colleagues examined cholesterol abnormalities among a consecutive sample of patients with self-harm behavior, but not genuine suicide attempts (i.e., parasuicidal patients). In this population, investigators also found a significantly lower mean serum cholesterol level.[35]

Studies with negative findings. As expected, several studies have found no association between low serum cholesterol levels and suicidal ideation.[20,26] There are also studies that indicate no relationship between low serum cholesterol levels and bonafide suicide attempts[36–40] or parasuicidal behavior.[41] Finally, among a cohort of schizophrenic patients, there was no association between low serum cholesterol levels and completed suicide.[42]

Interpretation of Available Data

Given these conflicting data, we suggest the following tentative conclusions. Despite the noted inconsistencies in empirical findings, there are a substantial number of studies that support a relationship between low serum cholesterol levels and depressive symptoms/disorders and suicidal ideation/suicide attempts. In affected individuals, this relationship appears most often to be an inverse one (i.e., that low serum cholesterol levels correlate with these various psychiatric phenomena). That the relationship is an inconsistent one does not necessarily imply that it is an invalid one. Rather, the inconsistency suggests that the relationship is probably a variable or a partial one (i.e., low serum cholesterol levels variably or partially contribute to or manifest with these psychiatric phenomena) that may only be relevant in some individuals. Given the role of variable or partial contribution, whether this relationship is genuinely causal (i.e., that low serum cholesterol levels contribute to the generation of psychopathology) or secondary (psychopathology results in low serum cholesterol levels) remains unknown.

Pathophysiology

If low serum cholesterol levels are genuinely associated with the described psychopathologies, what might be the pathophysiology of such a relationship? The pragmatic answer is that no one knows. Papakostas and colleagues offer some in-depth and complex hypotheses that might explain the relationship between low serum cholesterol levels and the discussed psychopathologies.[43] These explanations relate to cholesterol levels in cell membranes, inhibited neuronal growth, and attenuated serotonergic function. Other authors discuss the possible roles of serotonin transporters,[44] decreased serotonin receptors,[45] inter-relationships with leptin,[46] dietary intake,[47] decreased serotonin turnover,[48] interleukin-2,[49] and genetics.[50] Given the plethora of tentative possibilities, there is likely to be a very complex and/or an elusive psychobiological interface.

Medications and Effects on Cholesterol

Given that the preceding data is inconsistent, we suggest that the relationship between low serum cholesterol and depressive symptoms/disorders and suicidal ideation/attempts is not a strictly predictable one. Rather, it appears to be only partially and moderately specific. Given this tentative conclusion, is there any evidence that medications can cause simultaneous changes in serum cholesterol levels and mood?

Cholesterol-lowering medications and psychopathology. As expected, the literature on the psychiatric effects of cholesterol-lowering medications is controversial. For example, Boston, Dursun, and Reveley indicate that there is substantial evidence that lowering cholesterol levels with medications is associated with an increase in various psychiatric disorders (e.g., depression) and violent deaths—findings that emerged in cardiovascular primary prevention studies.[51] However, other investigators indicate that no such relationship is evident in their empirical studies.[52,53]

Psychotropic medications and cholesterol effects. In samples of depressed patients, several studies indicate that effective mood-disorder treatment results in an increase in serum cholesterol levels. These findings have been reported with various antidepressants and mood stabilizers,[54] doxepin,[55] imipramine,[56] paroxetine,[57] and even following treatment with electroconvulsive therapy.[58] However, in future studies, the explicit duration of drug treatment as well as weight status throughout the study of participants would have to be meticulously clarified.
As expected, there are also studies indicating that antidepressant treatment does not affect cholesterol levels. For example, there is a six-week study of trazodone[59] and a six-month study of bupropion—both with negative findings.[60]

Conclusions

Given the inconsistencies in the data, it appears that only some individuals with low serum cholesterol levels evidence depressive symptoms, mood disorders, suicidal ideation, and/or suicide attempts. Whether this metabolic peculiarity is causal or secondary to these psychopathologies is unknown. In addition, we do not know if this particular subgroup consistently responds to antidepressant treatment with an elevation in serum cholesterol levels. However, this area of investigation appears potentially fertile. Indeed, future investigations need to examine whether some individuals have a predisposition to depressive symptoms/mood disorders and suicidal ideation/suicide attempts that is presaged by low serum cholesterol levels; whether cholesterol assessment, in conjunction with the measurement of other metabolic or neurohormonal parameters, might suffice as a biological marker in some susceptible individuals; and whether in affected individuals, cholesterol elevation with treatment signifies a consistently good response to medications. Only further investigation will clarify these intriguing cholesterol quandaries.

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