Date Published: February 15, 2018
Publisher: Public Library of Science
Author(s): Piyoosh Kumar Singh, V. R. Rao, Gurudutt Pendyala.
Suicide is a spectrum of behavior including suicide ideation and suicidal attempt and is undoubtedly the outcome of the interaction of several factors. The role of two main constructs of human nature, aggression and impulsivity, has been discussed broadly in relation to suicide, as endophenotypes or traits of personality, in research and in clinical practice across diagnoses. The objective of our study was to assess impulsive and aggressive behaviors among primitive people of the Idu Mishmi tribe, who are known for high suicide completer and attempter rates.
The study group was comprised of 177 unrelated Idu Mishmi participants divided into two sets: 39 suicide attempters and 138 non-attempters. Data on demographic factors and details of suicide attempts were collected. Participants completed a set of instruments for assessment of aggression and impulsivity traits.
In the Idu Mishimi population we screened (n = 177), 22.03% of the individuals had attempted suicide, a high percentage. The suicide attempters also showed a significant sex difference: 35.9% were male and 64.10% were female (p = .002*). The suicide attempters (A) scored significantly higher than non-attempters (NA) on aggression (A = 23.93,NA = 18.46) and impulsivity (A = 75.53,NA = 71.59, with p value = 0.05). The trait impulsiveness showed a significantly higher difference (F (1, 117) = 7.274) in comparison to aggression (F (1, 117) = 2.647), suggesting a profound role of impulsiveness in suicide attempts in the Idu Mishmi population. Analysis of sub-traits of aggression and impulsivity revealed significant correlations between them. Using different models, multivariate logistic regression implied roles of gender (OR = 1.079 (0.05)) and impulsiveness (OR = 3.355 (0.013)) in suicide attempts.
Results demonstrate that gender and impulsivity are strong risk factors for suicide attempts in the Idu Mishmi population.
Many attempts have been made to define the complex behavior of suicide. A number of predictors have been implicated in suicidal behavior from different social, psychological, and biological dimensions. Across cultures, the most robust findings in suicide research are the differences between genders and age groups . The most dramatic increase overtime in suicide mortality rate has been observed in the third world countries India and China, due to their unique socioeconomic and behavioral patterns . Current research indicates that the presence of psychopathology is probably the single most important predictor of suicide and approximately 90% of suicide cases meet criteria for at least one psychiatric abnormality . The high prevalence of psychiatric disorders among suicide deaths and attempts has been observed and implicated as one of the best indicators of complex suicide behavior . JJ Mann et al. (2003) proposed the stress-diathesis model to investigate the role of other factors over and above psychopathology . Two main constructs of human nature, aggression and impulsivity, have been discussed broadly as endophenotypes or traits of personality, in relation to suicide, in research and in clinical practice across diagnoses [7, 8, 9]. Previous studies have established them as risk factors for suicide but it remains uncertain whether their effect on suicide is cumulative or independent. Current research indicates that the overlap between these constructs is robust, and they should be considered together, as a single “Impulsive-Aggression” phenotype . However, other viewpoints emphasize their distinct latent dimensions .
The study design of the present study is cross-sectional and the data set is comprised of 177 Idu Mishmi participants, of both sexes, aged 15–70 years (data in S1 Text), from families known to be suicide affected and un-affected, from Anini town, in the Dibang Valley district (altitude 1,968 m or 6,457 ft), Arunachal Pradesh state, India. Data were recorded using closed questionnaires and well-validated psychological tools in 30-minute-long, face to face, structured, in-depth interviews, after obtaining written consent. Participation was voluntary and no compensation was given to study participants. Demographic details including age, sex, marital status, education, and employment were collected by structured questionnaire. A psychiatric diagnosis of suicide attempts was based on the Columbia Suicide Severity Rating Scale (C-SSRS). Assessment of personality traits, aggression and impulsivity, was performed using the Modified Overt Aggression Scale (MOAS) and Barratt Impulsiveness Scale, 11th version (BIS-11) respectively. All the employed tools were used after pilot testing them in the Idu population and no modification was made to the schedules. Each participant’s responses were recorded in their preferred language (Hindi or English) by a trained anthropologist (PKS), as the population is multilingual.
In the Idu Mishmi population we identified suicide attempters who had made one attempt (n = 31, 17.51%), two attempts (n = 5, 2.82%), and three attempts (n = 3, 1.69%) in their lifetime. Among attempters Hanging (n = 20, 64.52%) and consumption of pesticide (n = 7, 22.58%) were the most preferred modes of both sexes.
This study reports a high rate of suicide attempts (22.03%) in the Idu Mishmi tribe of the Dibang Valley district of Arunachal Pradesh, India. The issue of suicide in the Idu Mishmi came to light with media reporting of suicide deaths in the Dibang Valley and Lower Dibang Valley, and was later validated by a scientific study in which 218 cases of suicide were reported, over four decades, in this tiny tribe numbering 15,000 . Further, our group has published the presence of high suicide attempt rates and psychiatric traits like depression, anxiety, and eating disorders among Idu Mishmi school children and family members in the lower Dibang district of Arunachal Pradesh . Ethnographic, anthropological, and sociological accounts of indigenous people from India and around the globe have posited the frequent presence of suicide behavior among primitive people [30, 3145, 46, 47]. Several attempts have been made to unmask the causative and risk factors like psychiatric abnormality, positive family history, alcoholism, depression, having a friend who has attempted suicide, history of physical abuse and sexual abuse, female sex, etc. [48,49]. The stress-diathesis model, which includes the role of childhood trauma and personality traits like impulsivity and aggression, is another attempt to illuminate the complex behavior of suicide . The population aggression score mean recorded in the Idu Mishmi population was 21.20. In a sex wise comparison, the male sex recorded a high mean value. In females, auto-aggression was found to be high. Research indicates that females were less likely to opt for direct physical violence and they can express their aggression though non-physical behaviour. Males, are quicker to show physical aggression and aggression against property. The outcome of this study, the significant differences shown between suicide attempters and non-attempters in the total aggression category, is validated by the shared neurobiology that has been proposed for suicide and aggressive behavior . Aggression has been observed to be concomitant with lowered serotonin-mediated brain activity, and a pattern of emotional dysregulation in the context of interpersonal difficulties and other stressful life events, all of which can result in suicide [10, 50].
The present study among the Idu Mishmi, an isolated endogamous tribal group, focuses on the presence of a high suicide attempt rate and sex variability. High scores on measures of aggression and impulsivity traits were recorded, with significant differences among suicide attempters and non-attempters. Male attempters were more at risk of impulsivity, whereas females showed greater risk for aggression, but in the total studied population, the suicide risk was almost three times higher with higher aggression, and almost twice as high with higher impulsivity. The subcategories of impulsivity were deeply correlated among themselves and with subcategories of aggression. Most of the previous studies emphasized considering suicide attempts to be the best diagnostic trait of suicidal behavior  and that it should possess the qualities of being self-initiated, potentially injurious behavior with the presence of intent to die and nonfatal outcome . This study validates a suspicion raised by earlier scholars, as the high intensity of aggression and impulsivity in indigenous populations and their association with suicide behavior was re-witnessed in the present population-specific study.
The limitation of small sample size is due to the small population size, low density, and difficult terrain of their habitation. We could not observe the interplay of psychiatric abnormalities and the traits of aggression or impulsivity due to the absence of a psychiatric clinic in the study area. Further, deaths due to suicide could not be quantified in the absence of postmortem based data.