Understanding the neurobiology of suicidal behavior

Psychological, autonomic, and serotonergic correlates of parasuicide among adolescent girls

Although parasuicidal behavior in adolescence is poorly understood, evidence suggests that it may be a developmental precursor of borderline personality disorder (BPD). Current theories of both parasuicide and BPD suggest that emotion dysregulation is the primary precipitant of self-injury, which serves to dampen overwhelmingly negative affect. To date, however, no studies have assessed endophenotypic markers of emotional responding among parasuicidal adolescents. In the present study, we compare parasuicidal adolescent girls (n=23) with age-matched controls (n=23) on both psychological and physiological measures of emotion regulation and psychopathology. Adolescents, parents, and teachers completed questionnaires assessing internalizing and externalizing psychopathology, substance use, trait affectivity, and histories of parasuicide. Psychophysiological measures including electrodermal responding (EDR), respiratory sinus arrhythmia, and cardiac pre-ejection period (PEP) were collected at baseline, during negative mood induction, and during recovery. Compared with controls, parasuicidal adolescents exhibited reduced respiratory sinus arrhythmia (RSA) at baseline, greater RSA reactivity during negative mood induction, and attenuated peripheral serotonin levels. No between-group differences on measures of PEP or EDR were found. These results lend further support to theories of emotion dysregulation and impulsivity in parasuicidal teenage girls.

Midlife suicide risk, partner's psychiatric illness, spouse and child bereavement by suicide or other modes of death: a gender specific study

STUDY OBJECTIVE

To describe gender specific suicide rates associated with partner's psychiatric disorder, loss of a spouse, or child by suicide or other causes, being a parent, and marital status.

DESIGN

Nested case-control study. Information on causes of death, psychiatric admission, marital status, children, and socioeconomic factors was obtained from routine registers.

SETTING

Denmark.

PARTICIPANTS

9011 people aged 25-60 years who committed suicide; 180 220 age-gender matched controls; 111 172 marital partners; 174 672 children.

MAIN RESULTS

The suicide risk in women whose partner had been first admitted with a psychiatric disorder after 31 December two years earlier was 6.9 (95% CI 3.6 to 13.0), whereas their male counterpart experienced a risk of 3.9 (2.7 to 5.6); p value gender difference = 0.39. Men who had lost their partner by suicide or other causes of death experienced a suicide risk of 46.2 (18.3 to 116.4) and 10.1 (6.5 to 15.8), respectively; the analogous risk among women were about one third: 15.8 (6.6 to 37.4) and 3.3 (1.5 to 7.2), respectively. Child bereavement by suicide or other causes imposed an approximate twofold risk increase in their parents, whereas being a parent was protective in women. Except for widows (1.6, 1.2 to 2.0) and widowers (3.0, 2.3 to 3.9) the suicide risk associated with being separated (2.0, 1.8 to 2.3), divorced (1.8, 1.7 to 2.0), never married (1.4, 1.3 to 1.6), cohabitant (1.2, 1.1 to 1.3) was virtually the same in the two sexes.

CONCLUSIONS

The suicide risk is associated with partner psychiatric illness. Conjugal bereavement is particularly indicative of suicide in men, and spousal suicide is particularly indicative of suicide. Child bereavement is associated with parental suicide, while being a parent is protective against suicide in women.

Neurotrophin levels in postmortem brains of suicide victims and the effects of antemortem diagnosis and psychotropic drugs

Suicide is a major public health problem but the neurobiological factors of risk are poorly understood. Recent studies have mentioned changes in the serotoninergic system and in neuronal plasticity, as well. The present investigation was undertaken to examine whether there is an abnormality in brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) proteins in suicide victims. The effect of diagnosis and drug treatments on the neurotrophins was also assessed. Thirty suicide victims (11 F/19 M) and twenty-four (10 F/14 M) drug-free non-suicide subjects, devoid of psychiatric or neurological disease, were examined. Antemortem diagnoses and toxicological analyses had been performed. The ventral prefrontal cortex (PFC), the hippocampus, and the entorhinal cortex were selected. BDNF and NT-3 levels were assayed either with the Western blot or with the ELISA method. Results indicated a significant decrease in BDNF and NT-3 levels in the hippocampus and PFC (only BDNF) but not in the entorhinal cortex, of suicide victims who were drug-free compared with non-suicide controls. The decrease was observed in all suicide victims, regardless of diagnosis. In drug-treated suicide victims, neurotrophin levels were not significantly different from non-suicide controls. This study supports a role of BDNF and NT-3 neurotrophin, in the pathophysiology of suicidal behavior. Anatomically, this role may implicate the hippocampus and the PFC but not the entorhinal cortex. The absence of change in BDNF and NT-3 levels of drug-treated suicide victims suggests that both neurotrophins are mediators of psychotropic drugs. A better understanding of the neurobiology of suicide could help detect populations at risk.

Suicidal behavior in the family and adolescent risk behavior

PURPOSE

The purpose of this study was to examine the prevalence and sociodemographic characteristics of adolescents exposed to suicide attempts and suicide deaths by a family member and to evaluate the separate associations between exposure to a family member's suicide attempts or suicide death and risk behaviors, social-emotional functioning, and family connectedness.

METHOD

We performed a cross-sectional analysis of data collected in 1995 for wave I of the National Longitudinal Survey of Adolescent Health (n = 5,918). The independent variable was the exposure to suicidal behavior by a family member during the past 12 months (death by suicide, suicide attempt, and no suicidal behavior). The dependent variables were substance use, suicidal behavior, violent behavior, perceived shortened life expectancy, emotional distress, and parental and adolescent reports of family connectedness.

RESULTS

In the year before the survey, 3.9% of adolescents experienced a family member's suicide attempt whereas 1.2% experienced a family member's death by suicide. In regression analyses adjusting for sociodemographic variables, adolescents who had experienced the suicide attempt of a family member were more likely than those with no exposure to report the following: cigarette and marijuana use, alcohol misuse, suicidal ideation and attempts, fighting and inflicting injuries, decreased life-expectancy, emotional distress, and decreased adolescent reports of parent-child and family connectedness. Adolescents who had experienced a family member's death by suicide were more likely to report marijuana use and alcohol misuse, suicidal ideation and attempts, inflicting severe injuries, and emotional distress.

CONCLUSIONS

Adolescents who have experienced suicide attempts or suicide deaths in the family show high levels of at-risk behaviors, most notably their own suicidal ideation and attempts.

Suicide attempts in an African schizophrenia population: an assessment of demographic risk factors

This study investigated demographic variables, including affected sibling pair status, as risk factors for suicidal behavior in schizophrenia patients of African (Xhosa) descent. Xhosa subjects with schizophrenia were interviewed with the Diagnostic Interview for Genetic Studies (DIGS) and then stratified into two groups: those with ( n = 90) and those without ( n = 364) a history of previous suicide attempts. Demographic parameters (including gender, age, and social circumstances, sib ship) were then compared across these groups. Demographic predictors of suicide included sib ship status ( p = 0.038; OR = 1.7) and age of onset of illness ( p = 0.008; OR = 2.5). On further analysis of suicide in siblings, only a minority of sib pairs was found to be concordant for a lifetime history of suicide attempts (3%). These findings raise the possibility that affected sib pair status may be protective in nature. Given the counter-intuitive nature of this finding, further work is needed to replicate it, and to explore possible underlying mechanisms.

Regional mRNA expression of a second tryptophan hydroxylase isoform in postmortem tissue samples of two human brains

Tryptophan hydroxylase (TPH) as rate limiting enzyme in the biosynthesis of serotonin plays a major role as candidate gene in several psychiatric disorders. Recently a second TPH isoform (TPH2) was identified in mice, which was exclusively expressed in the brain. We investigated whether the mRNA of the human homologue of this new TPH2 isoform is expressed in the human brain but not in peripheral tissues. The study was performed with postmortem specimen obtained from two subjects who died on cardiovascular failure. TPH2 mRNA levels were determined by quantitative real time RT-PCR. TPH2 mRNA was exclusively present in the human brains but not in the investigated peripheral tissues. Our finding may open up new research strategies for the analysis of the repeatedly observed disturbances in the serotonergic system in patients suffering from several psychiatric disorders.

Genetic variations in tryptophan hydroxylase in suicidal behavior: analysis and meta-analysis

BACKGROUND

Neurobiological studies implicate serotonergic dysfunction in suicidal behavior. Tryptophan hydroxylase (TPH), the rate-limiting enzyme in the biosynthesis of serotonin, plays a vital role in serotonin metabolism. Thus, variations in the TPH gene have been regarded as prime candidates in the susceptibility to suicidal behavior. The most widely studied genetic variations in the TPH gene, which are located in intron 7, yielded conflicting results in individual studies on suicide-related behavior.

METHODS

We performed a meta-analysis on a total of 898 patients and 1179 control subjects, in addition to our local association study in consecutively recruited suicide attempters (n=147) and healthy control subjects of German descent (n=326).

RESULTS

We observed a nonsignificant higher frequency of the TPH intron 7 A218 allele in our local group. The meta-analysis showed a weak yet highly significant increase in the frequency of the A218 allele (odds ratio [OR]: 1.33; 95% confidence interval [CI]: 1.17-1.50; p=.00002) and an over-representation of A-carriers (OR: 1.48; 95% CI: 1.22-1.79; p=.00005) in Caucasian suicide attempters/victims.

CONCLUSIONS

Our meta-analysis provides strong evidence for an association of suicide-related behavior with an A218 single-nucleotide polymorphism in the TPH gene in Caucasians. Because this variation do not seem to alter functional properties of the TPH gene or protein, functional variations remain to be identified and subsequently tested for association with suicide-related behavior.

Pet-1 ETS gene plays a critical role in 5-HT neuron development and is required for normal anxiety-like and aggressive behavior

The central serotonin (5-HT) neurotransmitter system is an important modulator of diverse physiological processes and behaviors; however, the transcriptional mechanisms controlling its development are largely unknown. The Pet-1 ETS factor is a precise marker of developing and adult 5-HT neurons and is expressed shortly before 5-HT appears in the hindbrain. Here we show that in mice lacking Pet-1, the majority of 5-HT neurons fail to differentiate. Remaining ones show deficient expression of genes required for 5-HT synthesis, uptake, and storage. Significantly, defective development of the 5-HT system is followed by heightened anxiety-like and aggressive behavior in adults. These findings indicate that Pet-1 is a critical determinant of 5-HT neuron identity and implicate a Pet-1-dependent program in serotonergic modulation of behavior.