Serum cholesterol, suicidal behavior and impulsivity in cocaine-dependent patients

How do lipids influence risk of violence, self-harm and suicidality in people with psychosis? A systematic review

OBJECTIVES

Low cholesterol has been linked with violent and suicidal behaviour in people with schizophrenia. This association, if consistently present, may be a promising biological marker that could assist clinicians in decision making regarding risk and treatment. We conducted a systematic review to assess whether there is a reliable association between lipid profile (total cholesterol, high- and low-density lipoprotein cholesterol, and triglycerides) and aggression, self-harm or suicide in people with schizophrenia, and whether effects are similar in males and females.

METHOD

Relevant databases were searched to identify primary research studies (up to November 2020) that (1) involved adults (some samples also included 16- to 18-year olds) with a confirmed diagnosis of schizophrenia, schizoaffective disorder or psychosis; and (2) included a standardised assessment of verbal aggression, physical aggression against objects, physical aggression against self (including suicide) or others. The search yielded 23 studies eligible for inclusion following a quality appraisal.

RESULTS

Suicidality was the most commonly assessed subtype of aggression (20 studies). For suicidality, about half the studies, including the study with the largest sample size, found a link with total cholesterol. An association between low total cholesterol and violence towards others was found in six of nine studies that investigated this. The evidence for a link with violence was the strongest for total cholesterol, followed by low-density lipoprotein cholesterol and high-density lipoprotein cholesterol, and the weakest for triglycerides. Only a few studies investigated sex differences and yielded mixed evidence. Studies focussed on self-harm as well as involving females in forensic settings were lacking.

CONCLUSION

There is encouraging evidence of an association between low total cholesterol and aggression towards others as well as suicidality in schizophrenia. Future studies should systematically explore this association in people with schizophrenia who have a significant history of violence, suicidality and self-harm, both inpatients and community, and also investigate underlying mechanisms.

Low cholesterol, impulsivity and violence revisited

PURPOSE OF REVIEW

To summarize the recent findings on the association of cholesterol levels with impulsivity and violence.

RECENT FINDINGS

Several authors have recently highlighted the importance of confounding factors that mask the association between cholesterol and impulsivity or violent behaviour. In particular, demographic factors and presence of psychiatric disorders can play a role in the discrepancies present in literature. Men seem to be more sensitive to low cholesterol levels as the association between low cholesterol levels and aggression is found mostly in men. Cholesterol may play a role as a moderator of the serotonergic function and interact with associations between relevant gene variants and impulsivity. Lowering cholesterol levels with statins brings about several changes in the serotonergic system, nerve cell membrane microviscosity and behaviour, and needs to be done with precaution in susceptible individuals. Cholesterol levels could serve as a biological risk marker for violence and suicidal tendencies in psychiatric patients with depression and schizophrenia.

SUMMARY

Future studies should consider the potential nonlinearity in the association of cholesterol levels with impulsivity, and dependence of the association on gender, psychiatric condition, and environmental factors.

Effect of a human serotonin 5-HT2A receptor gene polymorphism on impulsivity: Dependence on cholesterol levels

BACKGROUND

Impulsivity is multidimensional: Low impulse control may result in behavioural disorders, but acting on the spur of moment may also be advantageous. Previous studies have shown negative associations between different facets of impulsivity and serotonergic function. Other investigations have found negative correlations between serum lipid levels and impulsivity.

METHODS

We have investigated whether the functional polymorphism -1438A/G in the serotonin 5-HT_2A receptor gene (HTR2A) is associated with impulsivity levels and whether there is any interaction with serum lipid levels. This analysis was based on data of the population-representative Estonian Children Personality Behaviour and Health Study at age 25. Impulsivity was self-reported with the Adaptive and Maladaptive Impulsivity Scale.

RESULTS

Subjects with the A/A genotype of the HTR2A -1438A/G polymorphism had higher scores of Maladaptive impulsivity, but not Adaptive impulsivity. In females, high LDL and total cholesterol levels increased the genotype effect. In males, in the highest quartile of total or LDL cholesterol the genotype effect was altered, with G/G homozygotes having the highest Maladaptive impulsivity levels.

LIMITATIONS

Only one cohort of the European Youth Heart Study (EYHS) was used in the current study and impulsivity measures were self-reported.

CONCLUSIONS

Our results do not support the notion that low cholesterol levels universally lead to higher impulsivity, but it was found that high total and LDL cholesterol levels moderate the effect of the HTR2A gene promoter polymorphism. This suggests that future studies on impulsivity need to consider the interaction of serotonergic measures with the whole range of cholesterol levels.

Serum lipid levels and suicidality: a meta-analysis of 65 epidemiological studies

BACKGROUND

We conducted a systematic review and meta-analysis to determine the association between serum lipid levels and suicidality, as evidence from previous studies has been inconsistent.

METHODS

We identified relevant studies by searching Medline, Web of Science, EMBASE, and the Cochrane Database of Systematic Reviews (1980 to Dec. 5, 2014). Studies assessing the association between serum total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and/or triglycerides (TG) levels and suicidality were included. We used a random-effects model to take into account heterogeneity among studies.

RESULTS

We included 65 studies with a total of 510 392 participants in our analysis. Compared with the nonsuicidal patients, suicidal patients had significantly lower serum TC (weighted mean difference [WMD] -22.35, 95% confidence interval [CI] -27.95 to -16.75), LDL-C (WMD -19.56, 95% CI -26.13 to -12.99) and TG (WMD -23.40, 95% CI -32.38 to -14.42) levels, while compared with the healthy controls, suicidal patients had significantly lower TC (WMD -24.75, 95% CI -27.71 to -21.78), HDL-C (WMD -1.75, 95% CI -3.01 to -0.48) and LDL-C (WMD -3.85, 95% CI -7.45 to -0.26) levels. Furthermore, compared with the highest serum TC level category, a lower serum TC level was associated with a 112% (95% CI 40%-220%) higher risk of suicidality, including a 123% (95% CI 24%-302%) higher risk of suicide attempt and an 85% (95 CI 7%-221%) higher risk of suicide completion. The cut-off values for low and high serum TC level were in compliance with the categories reported in the original studies.

LIMITATIONS

A major limitation of our study is the potential heterogeneity in most of the analyses. In addition, the suicidal behaviour was examined using different scales or methods across studies, which may further explain heterogeneity among the studies.

CONCLUSION

We identified an inverse association between serum lipid levels and suicidality. More mechanistic studies are needed to further explain this association.

Potential neurochemical links between cholesterol and suicidal behavior

The role of cholesterol in psychiatric diseases has aroused the interest of the medical community, particularly in association with violent and suicidal behavior. Herein, we discuss some aspects of brain cholesterol metabolism, exploring possible mechanisms underlying the findings and reviewing the available literature on the possible neurochemical link between suicide and low or reduced levels of serum cholesterol. Most of the current hypotheses suggest a decreased serotonergic activity due to a decrease in cholesterol in the lipid rafts of synaptic membranes. Some aspects and limitations of this assumption are emphasized. In addition to serotonin hypofunction, other mechanisms have been proposed to explain increased impulsivity in suicidal individuals, including steroid modulation and brain-derived neurotrophic factor decrease, which could also be related to changes in lipid rafts. Other putative markers of suicidal behavior (e.g. protein S100B) are discussed in connection with cholesterol metabolism in the brain tissue.

Differences in cholesterol and metabolic syndrome between bipolar disorder men with and without suicide attempts

Patient with mental illnesses such as schizophrenia and bipolar disorder have an increased prevalence of metabolic syndrome (MetS) and its components compared to general population. Among psychiatric disorders, bipolar disorder ranks highest in suicidality with a relative risk ratio of completed suicide of about 25 compared to the general population. Regarding the biological hypotheses of suicidality, low blood cholesterol level has been extensively explored, although results are still conflicting. The aim of this study was to investigate whether there were differences in the serum cholesterol levels in hospitalized bipolar disorder men patients with history of suicide attempts (n= 20) and without suicide attempts (n= 20). Additionally, we investigated if there were differences in the prevalence of MetS according to NCEP ATP-III criteria in these two groups of patients. Results of the study indicated significantly lower serum cholesterol levels (P = 0.013) and triglyceride levels (P = 0.047), in the bipolar disorder men with suicide attempts in comparison to bipolar disorder men without suicide attempts. The overall prevalence of MetS was 11/40 (27.5%). On this particular sample it was higher in the non-attempters 8/20 (40.0%) than in attempters 3/20 (15.0%) bipolar men group, but without statistical significance. Lower concentrations of serum cholesterol might be useful biological markers of suicidality in men with bipolar disorder.

Differences in cholesterol and metabolic syndrome between bipolar disorder men with and without suicide attempts

Patient with mental illnesses such as schizophrenia and bipolar disorder have an increased prevalence of metabolic syndrome (MetS) and its components compared to general population. Among psychiatric disorders, bipolar disorder ranks highest in suicidality with a relative risk ratio of completed suicide of about 25 compared to the general population. Regarding the biological hypotheses of suicidality, low blood cholesterol level has been extensively explored, although results are still conflicting. The aim of this study was to investigate whether there were differences in the serum cholesterol levels in hospitalized bipolar disorder men patients with history of suicide attempts (N=20) and without suicide attempts (N=20). Additionally, we investigated if there were differences in the prevalence of MetS according to NCEP ATP-III criteria in these two groups of patients. Results of the study indicated significantly lower serum cholesterol levels (p=0.013) and triglyceride levels (p=0.047), in the bipolar disorder men with suicide attempts in comparison to bipolar disorder men without suicide attempts. The overall prevalence of MetS was 11/40 (27.5%). On this particular sample it was higher in the non-attempters 8/20 (40.0%) than in attempters 3/20 (15.0%) bipolar men group, but without statistical significance. Lower concentrations of serum cholesterol might be useful biological markers of suicidality in men with bipolar disorder.

Cholesterol and suicide attempts: a prospective study of depressed inpatients

Low cholesterol levels have commonly been associated with various suicide measures. We sought to examine suicide attempts in a prospective sample of depressed patients that on prior analysis demonstrated an association between low cholesterol and subsequent suicide completions. Seventy-four inpatients with Research Diagnostic Criteria unipolar major depression, bipolar depression or schizoaffective depression entered a prospective follow-up study from 1978 to 1981. Kaplan-Meier survival analysis and Cox regression were utilized to elucidate the relationship between cholesterol levels and subsequent severe suicide attempts as well as all suicide attempts regardless of severity. Attempts preceding index hospitalization and other lifetime attempts were evaluated cross-sectionally. Low serum cholesterol levels did not predict subsequent suicide attempts. Contrary to our hypothesis, the high cholesterol group was associated with increased risk of suicide attempts on survival analysis in those less than median age. Nonetheless, in cross-sectional analysis, the low cholesterol group had more suicide attempts preceding index hospitalization and more remote lifetime attempts. The results from this prospective dataset do not support an association between low cholesterol and subsequent suicide attempts despite replicating the retrospective findings of previous case-control and cross-sectional studies.

No relationship between serum cholesterol and suicidal ideation and depression in African-American diabetics

Low serum cholesterol has been associated with suicidal behavior. Depression has been postulated to be a mediating factor between low serum cholesterol and suicidal behavior. Therefore, this possibility was examined in a large group of 459 diabetic patients that had blood drawn for serum cholesterol levels on the same day that they completed the Beck Depression Inventory. The results failed to show any significant relationship between serum cholesterol levels and either total Beck Depression Inventory (BDI) scores or BDI scores on the item measuring current suicidal ideation. The limitations of the study are discussed.

Heroin overdose among young injection drug users in San Francisco

OBJECTIVES

We sought to identify prevalence and predictors of heroin-related overdose among young injection drug users (IDU).

METHODS

A total of 795 IDU under age of 30 years were interviewed in four neighbourhoods in San Francisco, California, USA. Participants were recruited as part of a broader study of HIV, hepatitis B and C among injecting drug users in San Francisco using street outreach and snowball techniques. Independent predictors of recent heroin overdose requiring intervention were determined using regression analysis.

RESULTS

Of 795 injecting drug users under age of 30 years, 22% (174/795) of participants reported a heroin overdose in the last year. In stepwise multiple logistic regression, independent predictors of recent heroin overdose were lifetime incarceration exceeding 20 months (odds ratio (OR) = 2.99, 95% confidence interval (CI) = 1.52-5.88); heroin injection in the last 3 months (OR = 4.89, 95% CI = 2.03-11.74); cocaine injection in the last 3 months (OR = 1.67, 95% CI = 1.14-2.45); injection of heroin mixed with methamphetamine in the last 3 months (OR = 1.74, 95% CI = 1.15-2.65); ever tested for hepatitis B or C (OR = 1.66 per year, CI = 1.09-2.54) and ever having witnessed another person overdose (OR = 2.89, 95% CI = 1.76-4.73).

CONCLUSIONS

Individuals with high levels of incarceration are at great risk of overdose, and prison or jail should be considered a primary intervention site. Further research on the role of cocaine and amphetamine in heroin-related overdose is indicated.

Suicidal behaviors and drug abuse: impulsivity and its assessment

Impulsivity appears to play an important role in suicidal behaviors and drug abuse, which are two psychiatric problems that may interact with one another. Interpretation of the literature on impulsivity in these behaviors may be complicated by the variety of measurement techniques for the assessment of impulsivity. There are three general types of impulsivity assessment: self-report, biological, and laboratory behavioral. Because laboratory behavioral measures both meet an operational definition of impulsivity and are sensitive to state-dependent changes in impulsivity, this paper presents data that focuses on laboratory behavioral performance among samples emitting suicidal behaviors or substance abuse. To better account for influence of impulsivity in these psychiatric disturbances, no single source of measurement should be used without the consideration of other types of instruments.

No evidence for an association between serum cholesterol and the course of depression and suicidality

In a number of previous reports, an association of altered, in most cases lower, serum cholesterol levels with depression, suicidal ideation and current or past suicidal behavior has been suggested. In this investigation, the course of serum cholesterol concentrations was measured in depressed patients during treatment. Ninety-two inpatients with a major depressive episode were included. Serum lipid concentrations were assessed at admission, after 1 week and after 4 weeks of antidepressant treatment. Degrees of depression and suicidality were measured with the Hamilton Depression Rating Scale. Although there was a significant reduction in depression and suicidality scores, neither a significant change in serum cholesterol levels nor a correlation between cholesterol levels and clinical improvement was found. Further, there were no significant differences in lipid levels between patients with and without a history of attempted suicide. In patients who had used a violent method, there was a trend for lower total cholesterol levels compared to those who had poisoned themselves. The results of this study do not support the hypothesis of an association of serum cholesterol with the course of depression and suicidal ideation. Cholesterol levels do not appear to be an appropriate biological marker for suicidality during the first 4 weeks of treatment in patients with a major depressive episode.

Serum cholesterol and impulsivity in a large sample of healthy young men

Studies that have investigated the association between cholesterol levels and impulsivity are relatively few in number and have yielded equivocal results. In this study, we investigated the relationship between impulsivity, depression and serum lipids [total cholesterol, high-density lipoprotein (HDL) cholesterol, and triglycerides] in a large sample (N=2051) of healthy young men who were remarkably homogeneous in terms of age, educational level, and socioeconomic conditions. Depression was assessed using the depression scale of the Minnesota Multiphasic Personality Inventory-2, and impulsivity was measured using the impulse control scale of the Big Five Questionnaire (BFQ). We found that subjects with a low serum cholesterol, defined as the lowest tenth of the total cholesterol distribution (< or =3.7 mmol/l), scored significantly lower on the impulse control scale of the BFQ. There was no significant association between depression and cholesterol concentrations. In addition, in a multiple regression model, both lower levels of total cholesterol and higher levels of HDL cholesterol emerged as significant predictors of impulsivity. However, since the regression model accounted for only 0.6% of the variance in the score on the impulse control scale of the BFQ, the biological significance of these correlations was negligible. Taken together, these findings suggest that, in healthy young men, a relationship between cholesterol and impulsivity emerges only when the statistical analysis focuses on subjects with very low levels of cholesterol.