افسردگی و خشونت: یک مطالعه از جمعیت سوئد

Background Depression increases the risk of a range of adverse outcomes including suicide, premature mortality, and self-harm, but associations with violent crime remain uncertain. We aimed to determine the risks of violent crime in patients with depression and to investigate the association between depressive symptoms and violent crime in a cohort of twins. Methods We conducted two studies. The first was a total population study in Sweden of patients with outpatient diagnoses of depressive disorders (n=47 158) between 2001 and 2009 and no lifetime inpatient episodes. Patients were age and sex matched to general population controls (n=898 454) and risk of violent crime was calculated. Additionally, we compared the odds of violent crime in unaffected half-siblings (n=15 534) and full siblings (n=33 516) of patients with the general population controls. In sensitivity analyses, we examined the contribution of substance abuse, sociodemographic factors, and previous criminality. In the second study, we studied a general population sample of twins (n=23 020) with continuous measures of depressive symptoms for risk of violent crime. Findings During a mean follow-up period of 3·2 years, 641 (3·7%) of the depressed men and 152 (0·5%) of the depressed women violently offended after diagnosis. After adjustment for sociodemographic confounders, the odds ratio of violent crime was 3·0 (95% CI 2·8–3·3) compared with the general population controls. The odds of violent crime in half-siblings (adjusted odds ratio 1·2 [95% CI 1·1–1·4]) and full siblings (1·5, 95% CI 1·3–1·6) were significantly increased, showing some familial confounding of the association between depression and violence. However, the odds increase remained significant in individuals with depression after adjustment for familial confounding, and in those without substance abuse comorbidity or a previous violent conviction (all p<0·0001). In the twin study, during the mean follow-up time of 5·4 years, 88 violent crimes were recorded. Depressive symptoms were associated with increased risk of violent crime and a sensitivity analysis identified little difference in risk estimate when all crimes (violent and non-violent) was the outcome. Interpretation Risk of violent crime was increased in individuals with depression after adjustment for familial, sociodemographic and individual factors in two longitudinal studies. Clinical guidelines should consider recommending violence risk assessment in certain subgroups with depression. Funding Wellcome Trust and the Swedish Research Council.

Depression is associated with increased risk of a wide range of adverse outcomes, including reduced life expectancy,1 suicide,2 self-harm,3 acute myocardial infarction,4 and a worse prognosis for comorbidities, such as heart disease and diabetes.5 and 6 Clinical experience and expert opinion7 also suggest an association with the risk of perpetrating violence, including homicide in male perpetrators.8 Consistent with this, community surveys in the UK,9 register-based investigations in Australia,10 and cohort studies in the USA11 and New Zealand12 report a link with violent outcomes. However, this finding is not consistent and no association was identified in a recent US longitudinal study with lifetime13 or past year14 diagnoses. Moreover, in studies showing associations, they have been largely confounded by comorbid alcohol or drug use13 or sociodemographic factors,15 or primarily noted in individuals with psychotic depression.16 The probable reason for these inconsistencies could be that many influential studies have included large proportions of inpatients, where the actual reason for admission might have been risk of violence to others, suicidality, psychosis, or comorbid substance abuse. Because these are strong risk factors for violence,17 they will amplify and perhaps explain any effects. Some studies have tried to control for these confounders, but none to our knowledge have also adjusted for familial effects. Familial effects could be a further explanation for the reported association with depression and could arise from common genetic predisposition or shared early environmental adversity. Mediation of mechanisms such as impulsivity and mood instability could be important as common causes of both depression and violence.18 To clarify these uncertainties, we conducted two complementary studies that benefit from use of databases available for research in Sweden. In the first, we longitudinally followed up patients with an index diagnosis of depression to determine risks of violent crime; only outpatients were included to avoid the probable biases associated with inpatient samples. Risks of violent crime were also investigated in non-depressed siblings to determine the extent of familial confounding, and a comparison was made with risks from suicide mortality. In the second study, we investigated the association between depressive symptoms and violent crime in a cohort of twins. These studies accordingly control for the major confounds we identify in the existing literature. Because clinical guidelines are inconsistent about assessment and management of violence risk in major depression, and lack information about risk factors,19 and 20 by contrast to self-harm and suicide for which risk assessment is clearly highlighted in guidelines19, 20 and 21 and expert opinion,22 we investigated such rates in the same cohort to compare risks across outcomes where clinical guidelines provide differing recommendations.

We identified 47 158 individuals (17 249 men and 29 909 women) with outpatient diagnoses of depression between 2001 and 2009 (table 1). Men had a mean age at first diagnosis of 32 years (SD 10) and women of 31 years (10). The mean time of follow-up was 3·0 years (SD 2·3) for men and 3·2 years (2·3) for women. Table 1. Descriptive data for risk factors in individuals with outpatient diagnoses of depression and control populations Depression Full siblings Maternal half-siblings Paternal half-siblings General population controls Men (n=17 249) Women (n=29 909) Men (n=14 345) Women (n=19 171) Men (n=3519) Women (n=3281) Men (n=4517) Women (n=4217) Men (n=329 307) Women (n=569 147) Sociodemographic factors Age at 1st diagnosis, years 32 (10) 31 (10) NA NA NA NA NA NA NA NA Income in lowest tertile 4835 (28%) 8093 (27%) 2298 (16%) 3422 (18%) 873 (25%) 895 (28%) 1267 (29%) 1229 (30%) 81 122 (25%) 143 941 (25%) Born abroad 3520 (20%) 5417 (18%) 927 (7%) 1324 (7%) 47 (1%) 47 (1%) 138 (3%) 119 (3%) 60 530 (18%) 105 114 (18%) Single 11 582 (67%) 17 862 (60%) .. .. .. .. .. .. 205 549 (60%) 321 175 (54%) Individual factors before diagnosis Alcohol abuse 902 (5%) 836 (3%) 294 (2%) 198 (1%) 100 (3%) 48 (2%) 102 (2%) 55 (1%) 4818 (1%) 5563 (1%) Drug abuse 715 (4%) 620 (2%) 173 (1%) 135 (1%) 72 (2%) 36 (1%) 74 (2%) 44 (1%) 2811 (1%) 2964 (1%) Alcohol crime 565 (3%) 99 (<1%) 195 (1%) 32 (<1%) 96 (3%) 17 (<1%) 109 (2%) 10 (<1%) 2791 (<1%) 629 (<1%) Drug crime 770 (5%) 209 (1%) 235 (2%) 73 (<1%) 97 (3%) 23 (1%) 109 (2%) 25 (1%) 3506 (1%) 1457 (<1%) Alcohol or drug medication 253 (2%) 108 (<1%) 39 (<1%) 12 (<1%) 6 (<1%) 0 5 (<1%) 3 (<1%) 713 (<1%) 455 (<1%) Any crime 6213 (36%) 3549 (12%) 3485 (24%) 1330 (7%) 1226 (35%) 336 (10%) 1514 (34%) 401 (10%) 67 942 (20%) 33 352 (6%) Violent crime 2322 (14%) 572 (2%) 1080 (8%) 188 (1%) 408 (12%) 56 (2%) 501 (11%) 54 (1%) 19 068 (6%) 4071 (1%) Non-violent crime 5749 (33%) 3282 (11%) 3268 (23%) 1262 (7%) 1152 (33%) 310 (9%) 1420 (31%) 384 (9%) 62 756 (18%) 31 485 (5%) Self-harm 910 (5%) 2362 (8%) 278 (2%) 509 (3%) 94 (3%) 146 (5%) 101 (2%) 135 (3%) 5187 (2%) 11 114 (2%) Data are mean (SD) or n (%). Income data were missing for 121 men and 253 women with depression, 134 men and 214 women with full siblings, 32 men and 23 women with maternal half-siblings, 72 men and 85 women with paternal half-siblings, and 14 341 men and 25 712 women in general population controls. NA=not applicable. Table options During follow-up, 641 men (3·7%) and 152 (0·5%) women with depression committed a violent crime, compared with 4097 (1·2%) men and 1059 (0·2%) women in age-matched and sex-matched controls. Those individuals with depression were at 3-fold increased odds of violent crime compared with general population controls (table 2). The odds of violent crime were between 1·1 and 1·7 for both full and half-siblings compared with the general population controls. We noted a trend for higher odds ratios in the full siblings, as would be predicted by a genetic model. By comparing odds ratios in cases and sibling analyses, indirect comparisons can be made of cases compared with siblings (figure). These analyses showed that individuals with depression had two-fold increased odds of violent crime risk compared with their unaffected siblings (table 2). Table 2. Adjusted odds ratios (aORs) and ratio of odds ratios (RORs) of violent crime in patients with depression, and in unaffected half-siblings and full siblings Patients with depression (n=47 158)* Paternal half-siblings (n=8734) Maternal half-siblings (n=6800) Full siblings (n=33 516) aOR (95% CI) ROR (95% CI) aOR (95% CI) ROR (95% CI) aOR (95% CI) ROR (95% CI) Overall 3·0 (2·8–3·3) 1·2 (1·1–1·4) 2·5 (2·2–2·9) 1·2 (1·1–1·4) 2·5 (2·2–2·8) 1·5 (1·3–1·6) 2·1 (1·8–2·4) Sex Male 3·1 (2·9–3·4) 1·2 (1·1–1·4) 2·5 (2·2–2·9) 1·2 (1·1–1·4) 2·5 (2·2–3·0) 1·4 (1·3–1·6) 2·2 (1·9–2·5) Female 2·8 (2·3–3·3) 1·2 (0·9–1·5) 2·4 (1·7–3·3) 1·2 (0·9–1·6) 2·3 (1·6–3·2) 1·7 (1·4–2·2) 1·6 (1·2–2·1) Without previous Alcohol or drugs 3·0 (2·8–3·3) 1·2 (1·1–1·4) 2·5 (2·2–2·9) 1·2 (1·0–1·3) 2·6 (2·2–3·0) 1·4 (1·3–1·6) 2·1 (1·9–2·4) Violent crime 3·0 (2·7–3·3) 1·2 (1·0–1·3) 2·6 (2·2–3·0) 1·2 (1·1–1·4) 2·4 (2·0–2·9) 1·5 (1·3–1·6) 2·1 (1·8–2·4) Any crime 2·7 (2·4–3·1) 1·1 (0·9–1·3) 2·4 (1·9–3·0) 1·3 (1·1–1·6) 2·0 (1·6–2·5) 1·4 (1·2–1·6) 1·9 (1·5–2·3) Self-harm 3·1 (2·8–3·4) 1·2 (1·1–1·3) 2·6 (2·2–3·0) 1·2 (1·1–1·4) 2·5 (2·2–2·9) 1·4 (1·3–1·6) 2·1 (1·9–2·4) All of above 2·6 (2·3–3·0) 1·1 (0·9–1·3) 2·3 (1·9–2·9) 1·3 (1·1–1·6) 2·0 (1·6–2·5) 1·4 (1·2–1·6) 1·9 (1·5–2·3) All aORs (adjusted odds ratios) are compared with general population controls and matched by age and sex. aOR analyses are adjusted for low family income and being born abroad. ROR=ratio of odds ratios. * Data are aOR (95% CI). Table options The odds of violent crime were similar for men with depression (compared with men without depression) and women with depression (compared with women without depression), and the relative risk increase remained significant when we excluded a history of previous violent and non-violent crimes, self-harm, and substance use disorders in both cases and controls (all p<0·0001; table 2). However, the presence of these pre-existing background factors led to notable changes in absolute risks of violent crime. A previous violent offending history had the largest effect—12·5% (n=291) of men and 3·8% (n=22) of women with this history committed a violent crime after a diagnosis of depression. The rates were further increased by addition of substance misuse and or self-harm (table 3). Combinations of risk factors increased absolute risk of violent crime to more than 15% in men, although the number of individuals with these combinations of risk factors was low (table 3). Table 3. Prevalence of risk factors and rates of violent crime in individuals with depression with different background risk factors Prevalence of risk factor by subgroup Rate of violent crime by subgroup Men (n=17 249) Women (n=29 909) Men Women Overall NA NA 641 (3·7%) 152 (0·5%) (1) Substance abuse 1466 (8·5%) 1353 (4·5%) 131 (8·9%) 28 (2·1%) (2) Self-harm 910 (5·3%) 2362 (7·9%) 59 (6·5%) 34 (1·4%) (3) Violent crime 2322 (13·5%) 572 (1·9%) 291 (12·5%) 22 (3·8%) (1) and (2) 279 (1·6%) 423 (1·4%) 26 (9·3%) 9 (2·1%) (1) and (3) 524 (3·0%) 115 (0·4%) 85 (16·2%) 6 (5·2%) (2) and (3) 266 (1·5%) 127 (0·4%) 40 (15·0%) 10 (7·9%) (1), (2), and (3) 123 (0·7%) 42 (0·1%) 20 (16·3%) 4 (9·5%) Not (1), (2), or (3) 13 497 (78·2%) 26 245 (87·7%) 291 (2·2%) 89 (0·3%) Data are n (%). NA=not applicable. Table options In those individuals with inpatient diagnoses between 2001 and 2009, the adjusted odds ratio of violent crime was higher at 5·7 (95% CI 5·2–6·2) than those with outpatient diagnoses only (3·0 [2·8–3·3]). In patients with depression, 3813 (8%) had a comorbid personality disorder; excluding those had no demonstrable effect on the adjusted odds ratio (aOR) of violence (aOR 3·1 [95% CI 2·8–3·3] compared with an aOR 3·0 [95% CI 2·8–3·3] in the whole sample). No significant differences were noted when outcomes were restricted to specific interpersonal crimes (homicide and attempted homicide, and all forms of assault; aOR 2·9, 95% CI 2·6–3·1). Rates and odds by type of violent crime are reported in the appendix p 1. Compared with 3·2 years of follow-up (793 violent crimes), non-significantly higher odds ratios were noted when we specifically examined violent crime within 3 months (aOR 3·6 [95% CI 2·8–4·5]; 87 violent crimes in depression sample), 6 months (3·3 [2·8–4·0]; 135 violent crimes), and 12 months (3·6 [3·2–4·1]; 346 violent crimes) of first diagnosis. In sensitivity analyses of the sibling sample (appendix pp 2–4), we noted no significant differences after inclusion of only older siblings or only younger siblings, or exclusion of siblings with follow-up before 2001. During a mean follow-up of 3·2 years, 575 (3·3%) men and 1287 (4·3%) women self-harmed (appendix p 5). These rates are comparable with the rates of violent crime described for men, but are higher for women. Self-harm in individuals with depression was increased compared with the general population (aOR 5·7, 95% CI 5·4–6·0). In the same period, 100 (0·6%) men and 41 (0·1%) women died by suicide (appendix p 5). Death by suicide was increased in patients with depression compared with the general population (aOR 6·7, 95% CI 5·5–8·1) and full siblings (ratio of odds ratio 2·9, 95% CI 2·2–3·8). In the twin sample (9834 men and 13 186 women), the mean age at questionnaire completion was 32·7 years (SD 8·2) for men and 32·5 years (8·2) for women. The mean sCESD score was 6·9 (SD 5·1) for men and 7·6 (5·9) for women. The mean time of follow-up was 5·3 years (SD 0·5) for men and 5·4 years (0·3) for women. During follow-up, 73 men (0·7%) and 15 (0·1%) women committed a violent crime, with a mean time-to-event of 1·5 years (SD 1·0) for men and 1·6 years (1·0) for women. The risk of violent crime significantly increased in those individuals with more depressive symptoms. In analyses of the association between depression and violent crime in co-twin analyses using standard Cox regression, the hazard ratio (HR; 95% CI) for all twins was 1·09 (1·06–1·13). For monozygotic twins, for which we used stratified Cox regression, the HR was 0·98 (0·82–1·18), and for dizygotic twins it was 1·07 (0·91–1·26). Statistical power was limited for further analyses of the twins by zygosity. In a sensitivity analysis of the twin sample, any crime was also significantly associated with increased depressive symptoms (HR 1·07, 95% CI 1·01–1·09).