Characteristics of the study population*
| Characteristic | Methylphenidate (n=8905) | No methylphenidate (n=88 293) | Proportion ratio (95% CI) |
| Sex | |||
| Men | 4839 (54.3%) | 47 907 (54.3%) | 1.0 (reference) |
| Women | 4066 (45.7%) | 40 386 (45.7%) | 1.0 (0.9 to 1.1) |
| Age | 36.5 years | 36.3 years | |
| 18–40 years | 5737 (64.4%) | 56 888 (64.4%) | 1.0 (reference) |
| 41–60 years | 2584 (29.0%) | 25 847 (29.2%) | 1.0 (0.9 to 1.1) |
| 61–80 years | 476 (5.3%) | 4718 (5.3%) | 1.0 (0.9 to 1.1) |
| >80 years | 108 (1.3%) | 840 (0.01%) | 1.3 (1.1 to 1.6) |
| Follow-up (days) | 1943 days | 1944 days | |
| BMI* | |||
| <25 | 864 (9.7%) | 5617 (6.4%) | 1.0 (reference) |
| 25–30 | 717 (8.1%) | 5746 (6.5%) | 0.8 (0.7 to 0.9) |
| >30 | 629 (7.1%) | 4702 (5.3%) | 0.9 (0.8 to 1.0) |
| Smoking* | |||
| Never | 2111 (23.7%) | 21 629 (24.5%) | 1.0 (reference) |
| Past | 723 (8.1%) | 4634 (5.2%) | 1.6 (1.5 to 1.8) |
| Current | 2292 (25.7%) | 13 111 (14.8%) | 1.8 (1.7 to 1.9) |
| Alcohol abuse | 352 (3.9%) | 878 (1.0%) | 4.1 (3.6 to 4.7) |
| Acute alcohol intoxication | 105 (1.2%) | 398 (0.5%) | 2.6 (2.1 to 3.3) |
| Tobacco abuse | 810 (9.1%) | 3930 (4.5%) | 2.2 (2.0 to 2.3) |
| Medicines abuse | 87 (0.9%) | 230 (0.3%) | 3.8 (3.0 to 4.8) |
| Drug abuse | 525 (5.9%) | 859 (1.0%) | 6.4 (5.7 to 7.1) |
| History of: | |||
| Organic psychosis (delier) | 37 (0.4%) | 157 (0.2%) | 2.3 (1.6 to 3.3) |
| Schizophrenia | 36 (0.4%) | 282 (0.3%) | 1.3 (0.9 to 1.8) |
| Affective psychosis | 82 (0.9%) | 245 (0.3%) | 3.3 (2.6 to 4.3) |
| Anxiety | 922 (10.4%) | 3602 (4.1%) | 2.8 (2.6 to 3.0) |
| Hypochondria/hysteria | 55 (0.6%) | 392 (0.4%) | 1.4 (1.1 to 1.9) |
| Depression | 1772 (19.9%) | 5252 (5.9%) | 4.3 (4.0 to 4.6) |
| Suicide (attempt) | 161 (1.8%) | 410 (0.5%) | 4.0 (3.3 to 4.8) |
| Burnout/overstrain | 886 (9.9%) | 3962 (4.5%) | 2.6 (2.4 to 2.8) |
| Other neuroses | 169 (1.9%) | 674 (0.7%) | 2.5 (2.1 to 3.0) |
| Personality disorder | 479 (5.4%) | 822 (0.9%) | 6.3 (5.6 to 7.0) |
| Other non-specified psychotic disorder | 80 (0.9%) | 372 (0.4%) | 2.2 (1.7 to 2.8) |
| Other psychiatric disorder | 541 (6.1%) | 1100 (1.2%) | 5.3 (4.7 to 5.9) |
| Total psychiatric | 3729 (41.9%) | 13 549 (115.3%) | 4.5 (4.3 to 4.7) |
| Previous or current use of: | |||
| Antipsychotics | 835 (9.4%) | 1884 (2.1%) | 4.8 (4.4 to 5.2) |
| Antidepressants | 3037 (34.1%) | 10 213 (11.6%) | 4.0 (3.8 to 4.2) |
| Anxiolytics | 3338 (37.5%) | 16 390 (18.6%) | 2.6 (2.5 to 2.8) |
| Sedatives | 2498 (28.1%) | 10 201 (11.6%) | 3.0 (2.8 to 3.1) |
*Values were missing for BMI (n=78 923), smoking (n=52 698).
BMI, body mass index.