Table 1:

Demographic, mental health and clinical covariates of emergency department visits for self-harm*

VariableUnmatched cohortMatched cohort
No. (%) of adolescents with no self-harm visits
n = 397 973
No. (%) of adolescents with ≥ 1 self-harm visits
n = 5832
Total
n = 403 805
DNo. (%) of adolescents with no self-harm visits
n = 10 731
No. (%) of adolescents with ≥ 1 self-harm visits
n = 5661
Total
n = 16 392
D
Demographic covariates
Age, yr, mean ± SD14.95 ± 1.4615.47 ± 1.2614.96 ± 1.460.3815.47 ± 1.2715.48 ± 1.2615.48 ± 1.270.00
Sex, female188 947 (47.5)4602 (78.9)193 549 (47.9)0.698345 (77.8)4444 (78.5)12 789 (78.0)0.02
Neighbourhood income quintile
 171 924 (18.1)1265 (21.7)73 189 (18.1)0.092385 (22.2)1225 (21.6)3610 (22.0)0.01
 273 747 (18.5)1091 (18.7)74 838 (18.5)0.002028 (18.9)1061 (18.7)3089 (18.8)0.00
 380 365 (20.2)1183 (20.3)81 548 (20.2)0.002169 (20.2)1149 (20.3)3318 (20.2)0.00
 487 268 (21.9)1197 (20.5)88 465 (21.9)0.032175 (20.3)1163 (20.5)3338 (20.4)0.01
 584 669 (21.3)1096 (18.8)85 765 (21.2)0.061974 (18.4)1063 (18.8)3037 (18.5)0.01
Rural69 467 (17.5)906 (15.5)70 373 (17.4)0.051556 (14.5)887 (15.7)2443 (14.9)0.03
Mental health and substance abuse covariates
Alcohol abuse2564 (0.6)463 (7.9)3027 (0.7)0.37661 (6.2)413 (7.3)1074 (6.6)0.05
Anxiety–neurotic disorders55 540 (14.0)3625 (62.2)59 165 (14.7)1.146434 (60.0)3454 (61.0)9888 (60.3)0.02
Behavioural and emotional disorders51 188 (12.9)2073 (35.5)53 261 (13.2)0.553715 (34.6)1941 (34.3)5656 (34.5)0.01
Behavioural syndromes associated with physiologic disturbances884 (0.2)52 (0.9)936 (0.2)0.0980 (0.7)49 (0.9)129 (0.8)0.01
Bipolar disorder or manic episode2953 (0.7)754 (12.9)3707 (0.9)0.501005 (9.4)664 (11.7)1669 (10.2)0.08
Disorders of personality and behaviour2170 (0.5)523 (9.0)2693 (0.7)0.40583 (5.4)446 (7.9)1029 (6.3)0.10
Disorders of psychological development8678 (2.2)388 (6.7)9066 (2.2)0.22593 (5.5)355 (6.3)948 (5.8)0.03
Eating disorders410 (0.1)216 (3.7)626 (0.2)0.27198 (1.8)166 (2.9)364 (2.2)0.07
Intellectual disability978 (0.2)46 (0.8)1024 (0.3)0.0863 (0.6)37 (0.7)100 (0.6)0.01
Mood disorders other than bipolar or mania12 101 (3.0)2353 (40.3)14 454 (3.6)1.023968 (37.0)2183 (38.6)6151 (37.5)0.03
Organic mental disorders639 (0.2)48 (0.8)687 (0.2)0.0979 (0.7)42 (0.7)121 (0.7)0.00
Other mental health disorders149 (0.0)57 (1.0)206 (0.1)0.1351 (0.5)48 (0.8)99 (0.6)0.05
Reaction to severe stress, and adjustment disorders8500 (2.1)1537 (26.4)10 037 (2.5)0.742402 (22.4)1383 (24.4)3785 (23.1)0.05
Schizophrenia1636 (0.4)282 (4.8)1918 (0.5)0.28415 (3.9)239 (4.2)654 (4.0)0.02
Substance abuse (non-alcohol)3906 (1.0)615 (10.5)4521 (1.1)0.42860 (8.0)550 (9.7)1410 (8.6)0.06
Suicidal ideation1807 (0.5)1134 (19.4)2941 (0.7)0.671195 (11.1)969 (17.1)2164 (13.2)0.17
Clinical covariates
Acne45 793 (11.5)805 (13.8)46 598 (11.5)0.071447 (13.5)785 (13.9)2232 (13.6)0.01
Asthma50 800 (12.8)837 (14.4)51 637 (12.8)0.051484 (13.8)797 (14.1)2281 (13.9)0.01
Cancers2054 (0.5)34 (0.6)2088 (0.5)0.0148 (0.4)33 (0.6)81 (0.5)0.02
Concussion or traumatic brain injury60 069 (15.1)1302 (22.3)61 371 (15.2)0.192243 (20.9)1234 (21.8)3477 (21.2)0.02
Congenital heart disease2906 (0.7)34 (0.6)2940 (0.7)0.0270 (0.7)34 (0.6)104 (0.6)0.01
Cystic fibrosis117 (0.0)≤ 5120 (0.0)0.01≤ 5≤ 56 (0.0)0.01
Diabetes mellitus4121 (1.0)87 (1.5)4208 (1.0)0.04134 (1.2)84 (1.5)218 (1.3)0.02
Down syndrome1268 (0.3)14 (0.2)1282 (0.3)0.0129 (0.3)14 (0.2)43 (0.3)0.00
Eczema80 290 (20.2)1345 (23.1)81 635 (20.2)0.072318 (21.6)1286 (22.7)3604 (22.0)0.03
Epilepsy4649 (1.2)117 (2.0)4766 (1.2)0.07189 (1.8)107 (1.9)296 (1.8)0.01
Inflammatory polyarthropathies2156 (0.5)36 (0.6)2192 (0.5)0.0162 (0.6)33 (0.6)95 (0.6)0.00
Migraine15 306 (3.8)419 (7.2)15 725 (3.9)0.15732 (6.8)400 (7.1)1132 (6.9)0.01
Neuromuscular conditions1477 (0.4)14 (0.2)1491 (0.4)0.0236 (0.3)14 (0.2)50 (0.3)0.02
Obesity10 340 (2.6)209 (3.6)10 549 (2.6)0.06352 (3.3)202 (3.6)554 (3.4)0.02
Psoriasis2361 (0.6)36 (0.6)2397 (0.6)0.0062 (0.6)35 (0.6)97 (0.6)0.01
Sickle cell anemia607 (0.2)6 (0.1)613 (0.2)0.018 (0.1)6 (0.1)14 (0.1)0.01
Spina bifida286 (0.1)≤ 5289 (0.1)0.01≤ 5≤ 58 (0.0)0.00
History of self-harm
Self-injury402 (0.1)124 (2.1)526 (0.1)0.19164 (1.5)109 (1.9)273 (1.7)0.03
Self-poisoning778 (0.2)260 (4.5)1038 (0.3)0.29338 (3.1)236 (4.2)574 (3.5)0.05
  • Note: D = standardized group difference, SD = standard deviation.

  • * In cells containing “ ≤ 5,” the actual count and percentage were suppressed to prevent reidentification of patients.

  • Unless stated otherwise.