|Year : 2014 | Volume
| Issue : 1 | Page : 38-44
Study of suicidal ideations, hopelessness and impulsivity in elderly
Surbhi C Trivedi, Neha K Shetty, Nitin B Raut, Alka A Subramanyam, Henal R Shah, Charles Pinto
Department of Psychiatry, Topiwala National Medical College and B.Y.L. Nair Ch. Hospital , Mumbai, India
|Date of Web Publication||29-Sep-2014|
Surbhi C Trivedi
Block No 5, Krishna Bhuvan, 67 Nehru Road, Vile Parle (East), Mumbai - 400057
Source of Support: None, Conflict of Interest: None
Aims and Objectives: This study aimed to assess the suicidal ideations, hopelessness and impulsivity in depressed and non-depressed elderly and to study the relationship of suicidal ideations with hopelessness and impulsivity in them.
Materials and Methods: This cross sectional study was done on 60 elderly patients (30 cases and 30 controls) above the age of 60 years. The scales used were Geriatric Suicide Ideation Scale, Beck Hopelessness Scale, Barrat's Impulsiveness Scale, Geriatric Depression Scale.
Results: Mean Geriatric Suicide Ideations Scale scores, mean Beck Hopelessness Scale scores and mean Barrat's Impulsiveness Scale and scores of depressed elderly were higher than that of elderly who were not depressed and these differences were statistically significant. Hopelessness was a significant predictor of suicidal ideation in the entire sample as well as in the depressed and non-depressed elderly when the two groups were considered separately. Impulsivity when considered alone was a significant predictor of suicidal ideations in the entire sample.
Conclusion: Hopelessness and impulsivity both by themselves are significant predictors for suicidal ideations in the elderly and when both are considered together hopelessness is a better predictor of suicidal ideations than impulsivity.
Keywords: Depression, elderly, hopelessness, impulsivity, suicidal ideation
|How to cite this article:|
Trivedi SC, Shetty NK, Raut NB, Subramanyam AA, Shah HR, Pinto C. Study of suicidal ideations, hopelessness and impulsivity in elderly
. J Geriatr Ment Health 2014;1:38-44
|How to cite this URL:|
Trivedi SC, Shetty NK, Raut NB, Subramanyam AA, Shah HR, Pinto C. Study of suicidal ideations, hopelessness and impulsivity in elderly
. J Geriatr Ment Health [serial online] 2014 [cited 2019 Aug 25];1:38-44. Available from: http://www.jgmh.org/text.asp?2014/1/1/38/141925
| Introduction|| |
Later life is a period that is associated with multiple losses along with changes in health status, autonomy, roles and relations. It is this change and sense of loss that may lead to a person to develop late life depression and eventually commit suicide. Traditionally the rates of completed suicides have been found to be highest in elderly males  with suicide rates in the age group of 15-24, 35-44, 55-64, 65-74, 75 and above in males being 22, 37.5, 42.1, 41, 50 respectively and in females being 4.9, 7.7, 10.6, 12.1, 15.8 respectively worldwide. Since the number of persons who attain old age is expanding, the absolute number of suicides is expected to rise and suicide is predicted to become the tenth most common cause of death in the world by the year 2020. 
Expression of suicidal ideations is a risk factor for death by suicide  and is an important clinical risk indicator of suicide in both the elderly as well as young. However, the elderly seem to be less prone to communicate their suicidal intentions.  Identifying predictors of suicidal ideation in older adults hence leads to an improved understanding of suicide risk in this age group. Some of the risk factors for suicidal ideation include being male, Caucasian, single, socially isolated, poor physical health,  loss of independence, cognitive decline, loss of self-esteem and diminished purpose or meaning in life. 
Many believe that suicide in late life is a rational response to painful old age. This reflects an incorrect belief that aging inevitably brings with it a host of physical, psychological and social insults and that there is a deep-seated dread of growing old and of dying more than the presence of reasoned thinking. Depression when it occurs in late life often occurs in the context of medical illness, physical and cognitive impairment,  social isolation, institutionalization, bereavement, impaired activities of daily living, and deteriorating physical health,  Having mental illness (particularly depression) is an important risk factor for suicide in the elderly. Depression is associated with a feeling of hopelessness  which is a term used to refer to complex affective, motivationaland cognitive tendencies resulting in a negative assessment of the future by the patient.  Mood disorders constitute an independent risk factor for suicide in elderly people and though physical illness and disability increase suicide risk their effect is also found to be mediated by depression.  Findings show that during initial assessment of elderly patients with major depression, severity of depression and previous serious attempts could predict the course of suicidal ideations.  Better recognition and treatment of both major and minor depression constitutes an important target for the prevention of suicide in the old elderly.  Suicidal elderly persons with depression require special attention during depression treatment because they have a lower overall response rate and need a longer duration for the response.  Though efficacious pharmacologic and psychosocial treatments are available, late-life depression still largely remains improperly diagnosed and insufficiently treated. 
Thoughts of insufficiency, hopelessness, guilt and despair are some of the reasons that lead a person with depression to consider suicide as a viable option. Hopelessness has been identified as a significant predictor of suicide-related ideation and behaviour. Beck's cognitive theory of suicide identifies hopelessness, a cognitive distortion involving negative future expectancies, as a key psychological variable driving suicidal processes. In the elderly it has been found that hopelessness is strongly related to suicidal ideation.  Elderly patients who have a suicide attempt in the past have significantly higher hopelessness scores than non-attempters and are also more likely to drop out of treatment. A high degree of hopelessness persisting after remission of depression in elderly patients appears to be associated with a history of suicidal behaviour. It also increases the likelihood of premature discontinuation of treatment and leads to future suicide attempts or suicide.  Therefore, hope and hopelessness play an active role in the dying process. Hope at the end of life can come in various forms: For cure, for survival, for comfort, for dignity, for intimacy, or for salvation. Hopelessness at the end of life is therefore not simply the absence of hope, but it is also attachment to a form of hope that is lost.  Hopelessness is expected to moderate the relationship between depression and suicidal ideation, as hopeless cognitions are often present in depressive states. Even though some suicide attempters and completers might not be depressed, but most are expected to be influenced by hopelessness.
Impulsive behaviour is also said to play an important role in suicidal ideation. The link between impulsivity and suicidal behaviour occurs because impulsive people tend to have a greater capability for suicidal behaviour, which they have acquired through experiencing painful and provocative events.  Though impulsivity in elderly suicide has not been studied much findings suggest that the impulse to self-harm may be even more pronounced among older adults and they are less likely to present as typically depressed. It is further suggested that impulsivity is more broadly associated with suicide-related ideations than hopelessness, and hence screening for impulsivity as well as hopelessness may help to increase clinicians' ability to identify older adults at greatest risk of self-harm. 
This study was undertaken with the aim of studying suicidal ideations in elderly depressed as compared to normal elderly population and two important predictors of suicidal ideations - hopelessness and impulsivity.
| Materials and methods|| |
This was a cross sectional study carried out in the Geriatric clinic of Psychiatry outpatient services (OPD) of a tertiary care teaching municipal institute in Mumbai after obtaining requisite approval by the Institutional Ethics committee. Subjects included 30 patients diagnosed as having depression as per DSM IV TR criteria with age of 60 years or more and having Geriatric Depression Scale (GDS) scores equal to or more than 5. Controls included 30 elderly with age of 60 years or more, with no known history of any psychiatric illness and having GDS scores equal to or above 5. The elder having any other present or past psychiatric illness, having uncontrolled medical or surgical disease and not willing to give consent for the study were excluded from both the groups. A written informed consent was taken from the subjects before commencing the study. The scales used were the Geriatric Depression Scale [GDS:SF], Geriatric Suicide Ideation Scale [GSIS], Beck Hopelessness Scale [BHS] and Barrat Impulsiveness Scale [BIS]. A semistructured proforma was used to collect the sociodemographic details of the subjects.
The Geriatric Depression Scale short form [GDS:SF] was developed in 1986 to screen for depression in older adults. It has been used in community, acute and long-term care settings. The GDS:SF consists of 15 questions requiring "yes" or "no" answers and can be completed quickly. Although the tool itself states that a score above 5 is suggestive of depression and a score equal to or greater than 10 is almost always indicative of depression, a more detailed scoring is often more helpful in rating depression. It was modified from the original 30-item form to focus on items with the highest correlation to depressive symptoms in validation studies.  The GDS:SF has demonstrated moderate reliability. A study  in 2005 in community-dwelling older primary care patients found moderate internal consistency reliability (with a Cronbach alpha of 0.749); good construct validity, with significant associations between the GDS:SF and measures of depressed mood and life satisfaction.
The Geriatric Suicide Ideation Scale [GSIS] is a multidimensional measure of suicidal ideation for seniors. It is composed of 31 questions with scores ranging from 31 to 155. Responses are rated on a 5 point Likert scale ranging from strongly disagree (1) to strongly agree (5). It has four factors reflecting the themes of Suicide Ideation, Death Ideation, Loss of Personal and Social Worth and Perceived Meaning in Life (reverse keyed). Cronbach's alpha (α) for GSIS total scores was α = 0.93 (r = 0.54) in a sample of 107 adults aged 65 years or older suggesting a good internal consistency. Test-retest reliability is strong for GSIS total score (r = 0.86, P < 0.001). Convergent validity was indicated by significant positive associations among GSIS scores and depression (GDS), social hopelessness (SHQ), and poor perceived physical health, and by negative associations with psychological well-being (PWB) and life satisfaction (SWLS). 
The Beck Hopelessness Scale [BHS]  was designed to measure negative attitudes about one's future and perceived inability to avert negative life occurrences. Twenty true or false questions measure 3 aspects of hopelessness: Negative feelings about the future, loss of motivation, and pessimistic expectations. BHS totals range from 0 to 20, with higher scores indicating greater hopelessness. The statements are designed to assess the extent of positive and negative beliefs about the future during the past week. Each of the 20 statements is scored 0 or 1. Across 7 clinical samples, reported internal consistency of BHS responses range from α = 0.82 to α = 0.93. When comparing clinical ratings and BHS scores, reported correlation coefficients between BHS responses and ratings of hopelessness have been reported as r = 0.74 in a general practice sample and r = 0.62 in a suicide-attempt sample. Test-retest reliability coefficients are modest (α = 0.69 and α = 0.66, 1 and 6 weeks thereafter, respectively).
The Barrat Impulsiveness Scale [BIS] version 11 is a self-report questionnaire administered to assess the frequency of impulsive and impulse-related thoughts and behaviours. Participants respond to 30 statements with response alternatives ranging from (1) rarely or never to (4) almost always or always. The 30 self-report items are scored between 0 to 4. The BIS-11 is worded to indicate non-impulsiveness to avoid a response set. Cumulative scores range from 30 (low in trait-impulsivity) to 120 (high in trait-impulsivity). Internal consistency of responses to the BIS have been reported to range from α = 0.79 to α = 0.83.  BIS-11 has a three factor subscale model of impulsivity determined by factor analysis that includes:
- Motor, or acting without thinking/on the spur of the moment, task persistence and perseverance,
- Attentional, the inability to focus on tasks at hand and cognitive instability, and
- Nonplanning, not thinking carefully, self-control, or cognitive complexity.
The structure of the instrument allows for the assessment of six first-order factors (attention, motor, self-control, cognitive complexity, perseverance, cognitive instability) and three second-order factors attentional impulsiveness [attention and cognitive instability], motor impulsiveness [motor and perseverance], non-planning impulsiveness [self-control and cognitive complexity].
Statistical analysis was done using Statistical Package for Social Sciences 19 th version (SPSS 19) software. Independent sample t tests were done to compute the statistical difference between the continuous variables among those who were depressed and not depressed. Multiple Regression analysis using the forward enter method was used to determine the power of hopelessness and impulsivity in predicting suicidal ideation in the sample. Multiple Regression analysis using the forward enter method was used to determine the power of depression, hopelessness and impulsivity in predicting suicidal ideation in the depressed elderly. Simple Regression was computed to determine the power of impulsivity alone as a factor in predicting suicidal ideation in this sample.
| Results|| |
The demographic details of the sample studied are shown in [Table 1].
|Table 1: Distribution of demographic variables in between the depressed and non-depressed group|
Click here to view
3 main aspects of depression were assessed viz. Suicidal ideation, Hopelessness and Impulsivity.
Results showed that the mean GSIS scores of depressed patients (mean −90.03) was higher than the mean GSIS scores of patients who were not depressed (mean −52.93), and this difference was tested to be statistically significant (t = 7.87, P < 0.001).
The mean BHS scores of depressed patients (mean −9.70) was higher than the mean BHS scores of patients who were not depressed (mean −1.13), and this difference was also tested to be statistically significant (t = 6.74, P < 0.001).
Similarly the mean BIS scores of depressed patients (mean −61.23) was higher than the mean BIS scores of patients who were not depressed (mean −51.94), and this difference was found to be statistically significant (t = 4.44; P < 0.001). Further assessment of relationship of various second order factors of BIS with depression was done. Results show that the mean scores of depressed were higher than mean scores of non-depressed on the dimension of attention and this difference was tested to be statistically significant (t = 4.34, P < 0.001). Also the mean scores of depressed were higher than mean scores of non-depressed on the non-planning dimension and this difference was tested to be statistically significant (t = 4.50, P < 0.001). But the difference in motor dimension was found to be statistically insignificant (t = 6.17, P = 0.539).
Multiple regression using the forward enter method was computed to determine the power of hopelessness and impulsivity in predicting suicidal ideations in the entire sample [Table 2]. Hopelessness (Beta = 0.847, P < 0.001) was found to be a significant predictor of suicidal ideation. The overall model fit was F = 96.66, P < 0.001, and 77% of the variance in suicidal ideations was predicted by hopelessness (R Square = 77%). It was observed that when entered with hopelessness in the above model, impulsivity was not a significant predictor of suicidal ideation.
|Table 2: Shows the relationship of suicidal ideations with hopelessness and impulsivity in the entire sample|
Click here to view
However, it was observed that when impulsivity was entered alone (Simple regression) it was a significant predictor of suicidal ideations (Beta = 0.395, P = 0.002) in the entire sample [Table 2]. It was observed that in this model (F =10.69, P = 0.002) only 15% of the variance in suicidal ideations was predicted by impulsivity (R square = 15%).
Further when the sample was divided into two groups of depressed and non-depressed, hopelessness (Beta = 0.800, P < 0.001) was a significant predictor of suicidal ideations in patients who were depressed. The overall model fit was F = 24.11, P < 0.001, and 61% of the variance in suicidal ideations was predicted by hopelessness (R Square = 61%).
Also hopelessness (Beta = 0.657, P < 0.001) was a significant predictor of suicidal ideations in patients who were not depressed. The overall model fit was F = 11.58, P < 0.001, and \46% of the variance in suicidal ideations was predicted by hopelessness (R Square = 46%).
Multiple Regression using the forward enter method was computed to determine the power of severity of depression, hopelessness and impulsivity in predicting suicidal ideations in the depressed elderly [Table 3]. Results indicated that among those patients who were depressed only hopelessness (Beta = 0.685, P = 0.001) was a significant predictor of suicidal ideations. This model showed that severity of depression (Beta = 0.146, P = 0.453) and impulsivity (Beta = 0.132, P = 0.271) were not significant predictors of suicidal ideations when considered with hopelessness. The overall model fit was F = 16.02, P < 0.001, and it showed that 60% of the variance in suicidal ideations was predicted by hopelessness (R Square = 60%).
|Table 3: Shows the relationship of suicidal ideations with severity of depression, hopelessness and impulsivity in the depressed elderly group|
Click here to view
| Discussion|| |
Suicidal ideations refers to recurrent thoughts of suicide, intent of committing it and/or planning of how to commit suicide. Results of this study showed that suicidal ideations are significantly more in elderly who are depressed. This is consistent with findings of a study by Turvey et al.  who showed that amongst the various risk factors for late life suicide, depressive symptoms showed the strongest association with late-life suicide. A study by Neufeld et al.  showed that suicide related ideations among older adults is strongly associated with depressive symptoms.
Hopelessness, one of the components of Beck's cognitive triad, is the despair that a person faces when he abandons the hope of comfort or success and is a cognitive characteristic that is believed to influence the formation of suicidal thoughts. Hopelessness was found to be significantly more in depressed elderly compared to non-depressed in this study. A study by Zunghas  similarly showed that feeling of hopelessness is more in elderly depressed people. Trenteseau et al.  also showed that hopelessness is related to depression, especially the psychological components of depression and behaviour.  In our study it was also found that in the entire sample as a whole, increase in hopelessness will bring about a significant increase in suicidal ideations. When further divided into depressed and non-depressed groups we found that increase in hopelessness will bring about a significant increase in suicidal ideations in both the groups independently. Also in those who are depressed when hopelessness, severity of depression and impulsivity were considered, amongst the three factors, hopelessness was again the single most important factor in predicting suicidal ideations. In contrast a study by Frierson  has shown that hopelessness is not related to suicidal ideations or behaviour in elderly. Similar to our study, a study by Uncapher
et al.  showed that the participants with more negative expectancies toward the future were more likely to be having suicidal thoughts. However they found that hopelessness did not predict suicidal ideations better than depression whereas in our study hopelessness was a more significant predictor of suicidal ideation than depression. The study by Neufeld et al.  similarly found that the single strongest predictor among the independent variables of depressive symptomatology, hopelessness and impulsivity, is hopelessness. However of note is the near complete absence of hopelessness in patients who were not overtly depressed and impulsivity being more pronounced in this group and the fact that impulsivity appeared to predict suicide-related ideations more broadly than hopelessness alone, with and without a broad presentation of depressive symptomatology in the study by Neufeld et al. 
Impulsivity is defined as the tendency to act without adequate thought and without regard to the negative consequences of these actions. Impulsivity was also found to be significantly higher in elderly depressed compared to non-depressed. Similarly impulsivity has been shown to be a distinct personality factor that may contribute to the onset of depressive illness in adults in a study by Grano et al.  Also Takahashi et al.  showed that depressive patients were more impulsive and time-inconsistent in inter-temporal choice action for gain and loss, in comparison to healthy controls.  On further studying the relationship between impulsivity and depression we found that on second order factor scores attentional impulsivity defined as lack of cognitive persistence with inability to tolerate cognitive complexity and non-planning impulsivity defined as a tendency to choose a small, more immediate reward over a larger, more delayed reward, and centred on the present orientation, associated with a lack of planning for the future and foresight had a significant relation with depression whereas motor impulsivity defined as acting without thinking, on the spur of the moment, with lack of thoughtfulness, was not significantly related to depression. Though certain studies  suggest that higher levels of impulsive traits play a greater role in suicide occurring among younger individuals and that these traits have decreasing importance with increasing age, however our study shows that an increase in impulsivity will also play a significant role in increasing suicidal ideations in the elderly.
To summarise, we found that suicidal ideations, hopelessness and impulsivity are seen more in depressed elderly compared to non-depressed elderly. Hopelessness is a significant predictor of suicidal ideations while impulsivity when considered on the same regression analysis was not a significant predictor of suicidal ideation in the sample. However, as an independent variable impulsivity did predict suicidal ideation significantly in the entire sample. Hopelessness also predicted suicidal ideations better than did the severity of depression in the depressed elderly.
Hence, we conclude that hopelessness is an important factor determining suicidal ideations in elderly population in depressed as well as non-depressed. So screening for hopelessness is necessary to find out the suicidal ideations in elderly population. Being a stronger predictor than depression it is necessary that after treating the patient for depression, mental health professionals still need to look out for hopelessness in the patients because even after depression remits if levels of hopelessness do not significantly change, suicidal ideation may still be persistent in the elderly population. Also, although impulsivity is generally overlooked in cases of elderly suicide we need to pay attention to impulsivity also as a risk factor while determining the risk of self-harm in elderly population as paying attention to impulsivity will help us target a critical factor for averting elderly suicide.
| Acknowledgements|| |
Dr. Ravindra Kamath, Professor and Head of Department, Department of Psychiatry, TN Medical College and BYL Nair Ch. Hospital, Mumbai, for his continuous support and guidance.
Dr. Sunitha Shankar (PhD) for her help in statistical analysis.
| References|| |
|1.||World Health Organization. Available from: http://www.who.int/mental_health/prevention/suicide/suicideprevent/en/. [Last accessed on 2011 Jun 5]. |
|2.||From what will we die in 2020? Lancet 1997;349:1263. |
|3.||Brown GK, Beck AT, Steer RA, Grisham JR. Risk factors for suicide in psychiatric outpatients: A 20-year prospective study. J Consult Clin Psychol 2000;68:371-7. |
|4.||De Leo D, Ormskerk SC. Suicide in the elderly: General characteristics. Crisis 1991;12:3-17. |
|5.||Conwell Y. Suicide among elderly persons. Psychiatr Serv 1995;46:563-4. |
|6.||Rosowsky E. Suicidal behaviour in the nursing home and a postsuicide intervention. Am J Psychother 1993;47:127-42. |
|7.||NIH consensus conference. Diagnosis and treatment of depression in late life. JAMA 1992;268:1018-24. |
|8.||Palsson S, Skoog I. The epidemiology of affective disorders in the elderly: A review. Int Clin Psychopharmacol 1997;12(Suppl 7): S3-13. |
|9.||Haaga DA, Dyck MJ, Ernst D. Empirical status of cognitive theory of depression. Psychol Bull 1991;110:215-36. |
|10.||Beck AT. Thinking and depression. I. Idiosyncratic content and cognitive distortions. Arch Gen Psychiatry 1963;9:324-33. |
|11.||Conwell Y, Duberstein PR, Caine ED. Risk factors for suicide in later life. Biol Psychiatry 2002;52:193-204. |
|12.||Alexopoulos GS, Bruce ML, Hull J, Sirey JA, Kakuma T. Clinical determinants of suicidal ideation and behavior in geriatric depression. Arch Gen Psychiatry 1999;56:1048-53. |
|13.||Waern M, Rubenowitz E, Wilhelmson K. Predictors of suicide in the old elderly. Gerontology 2003;49:328-34. |
|14.||Szanto K, Mulsant BH, Houck P, Dew MA, Reynolds CF 3 rd . Occurrence and course of suicidality during short-term treatment of late-life depression. Arch Gen Psychiatry 2003;60:610-7. |
|15.||Bruce ML, Ten Have TR, Reynolds CF 3 rd , Katz II, Schulberg HC, Mulsant BH, et al. Reducing suicidal ideation and depressive symptoms in depressed older primary care patients: A randomized controlled trial. JAMA 2004;291:1081-91. |
|16.||Uncapher H, Gallagher-Thompson D, Osgood NJ, Bongar B. Hopelessness and suicidal ideation in older adults. Gerontologist 1998;38:62-70. |
|17.||Rifai AH, George CJ, Stack JA, Mann JJ, Reynolds CF 3 rd . Hopelessness in suicide attempters after acute treatment of major depression in late life. Am J Psychiatry 1994;151:1687-90. |
|18.||Sullivan MD. Hope and hopelessness at the end of life. Am J Geriatr Psychiatry 2003;11:393-405. |
|19.||Bender TW, Gordon KH, Bresin K, Joiner TE Jr. Impulsivity and suicidality: The mediating role of painful and provocative experiences. J Affect Disord 2011;129:301-7. |
|20.||Neufeld E, O'Rourke N. Impulsivity and hopelessness as predictors of suicide-related ideation among older adults. Can J Psychiatry 2009;54:684-92. |
|21.||Sheikh JI, Yesavage JA. Geriatric Depression Scale (GDS): Recent evidence and development of a shorter version. Clin Gerontol 1986;5:165-73. |
|22.||Friedman B, Heisel MJ, Delavan RL. Psychometric properties of the 15-item geriatric depression scale in functionally impaired, cognitively intact, community-dwelling elderly primary care patients. J Am Geriatr Soc 2005;53:1570-6. |
|23.||Heisel MJ, Flett GL. The development and initial validation of the geriatric suicide ideation scale. Am J Geriatr Psychiatry 2006;14:742-51. |
|24.||Beck AT, Steer RA. Manual for the Beck Hopelessness Scale. San Antonio, TX: Psychological Corporation; 1988. |
|25.||Patton JM, Stanford MS, Barratt ES. Factor structure of the Barratt impulsiveness scale. J Clin Psychol 1995;51:768-74. |
|26.||Turvey CL, Conwell Y, Jones MP, Phillips C, Simonsick E, Pearson JL, et al. Risk factors for late-life suicide: A prospective, community-based study. Am J Geriatr Psychiatry 2002;10:398-406. |
|27.||Zung WW. Depression in the normal aged. Psychosomatics 1967;8:287-92. |
|28.||Trenteseau JA, Hyer L, Verenes D, Warsaw J. Hopelessness among later-life patients. J Appl Gerontol 1989;8:355-64. |
|29.||Frierson RL. Suicide attempts by the old and the very old. Arch Intern Med 1991;151:141-4. |
|30.||Granö N, Keltikangas-Järvinen L, Kouvonen A, Virtanen M, Elovainio M, Vahtera J, et al. Impulsivity as a predictor of newly diagnosed depression. Scand J Psychol 2007;48:173-9. |
|31.||Takahashi T, Oono H, Inoue T, Boku S, Kako Y, Kitaichi Y, et al. Depressive patients are more impulsive and inconsistent in intertemporal choice behavior for monetary gain and loss than healthy subjects--an analysis based on Tsallis' statistics. Neuro Endocrinol Lett 2008;29:351-8. |
|32.||McGirr A, Renaud J, Bureau A, Seguin M, Lesage A, Turecki G. Impulsive-aggressive behaviours and completed suicide across the life cycle: A predisposition for younger age of suicide. Psychol Med 2008;38:407-17. |
[Table 1], [Table 2], [Table 3]