Table 2.
Associations between ADHD and psychiatric and neurodevelopmental disorders among the siblings of cases and matched controls
| ADHDa | Adjustedb (model I) | Adjustedc (model II) | Adjustedd (model III) | |||||
|---|---|---|---|---|---|---|---|---|
| Case n = 7369 (%) | Control n = 23 181 (%) | RR | (95% CI) | RR | (95% CI) | RR | (95% CI) | |
| ADHD | 1134 (15.4) | 598 (2.6) | 7.1 | (6.4–7.8)*** | 6.5 | (5.9–7.2)*** | 5.7 | (5.1–6.3)*** |
| Conduct and oppositional disorders | 705 (9.6) | 461 (2.0) | 5.6 | (5.0–6.3)*** | 5.0 | (4.5–5.7)*** | 4.0 | (3.5–4.5)*** |
| ASD | 322 (4.4) | 264 (1.1) | 4.6 | (3.9–5.4)*** | 4.4 | (3.7–5.2)*** | 3.9 | (3.3–4.6)*** |
| Other emotional and social interaction disorders | 533 (7.2) | 530 (2.3) | 3.7 | (3.3–4.2)*** | 3.4 | (3.0–3.9)*** | 2.7 | (2.4–3.1)*** |
| Learning and coordination disorders | 1538 (20.9) | 1928 (8.3) | 3.0 | (2.8–3.2)*** | 2.8 | (2.6–3.0)*** | 2.6 | (2.4–2.8)*** |
| Tic disorders | 93 (1.3) | 123 (0.5) | 2.7 | (2.0–3.5)*** | 2.6 | (2.0–3.5)*** | 2.5 | (1.9–3.3)*** |
| Intellectual disability | 226 (3.1) | 278 (1.2) | 2.8 | (2.4–3.4)*** | 2.5 | (2.1–3.0)*** | 2.4 | (2.0–2.8)*** |
| Bipolar disorder | 82 (1.1) | 124 (0.5) | 2.2 | (1.7–3.0)*** | 2.3 | (1.7–3.0)*** | 1.9 | (1.4–2.6)*** |
| Unipolar mood disorders | 906 (12.3) | 1445 (6.2) | 2.2 | (2.1–2.4)*** | 2.2 | (2.0–2.4)*** | 1.9 | (1.7–2.0)*** |
| Schizophrenia spectrum disorders | 147 (2.0) | 249 (1.1) | 2.1 | (1.7–2.5)*** | 2.1 | (1.7–2.6)*** | 1.8 | (1.5–2.3)*** |
| Other neurotic and personality disorders | 218 (3.0) | 391 (1.7) | 2.0 | (1.7–2.3)*** | 2.0 | (1.7–2.4)*** | 1.7 | (1.4–2.0)*** |
| Alcohol and drug addiction/abuse | 316 (4.3) | 513 (2.2) | 2.1 | (1.8–2.4)*** | 2.0 | (1.8–2.3)*** | 1.7 | (1.5–2.0)*** |
| Anxiety disorders | 503 (6.8) | 1050 (4.5) | 1.7 | (1.5–1.9)*** | 1.6 | (1.5–1.8)*** | 1.4 | (1.3–1.6)*** |
| Eating disorders | 111 (1.5) | 344 (1.5) | 1.2 | (0.9–1.4) | 1.2 | (0.97–1.5) | 1.1 | (0.9–1.4) |
| Pooled diagnostic classes | ||||||||
| Any psychiatric/neurodevelopmental disorder | 3254 (44.2) | 5154 (22.2) | 2.4 | (2.3–2.5)*** | 2.3 | (2.2–2.4)*** | 2.1 | (2.0–2.2)*** |
| Any childhood-onset disorder | 2703 (36.7) | 3557 (15.3) | 2.9 | (2.8–3.1)*** | 2.7 | (2.6–2.9)*** | 2.5 | (2.4–2.6)*** |
ADHD, attention-deficit hyperactivity disorder; ASD, autism spectrum disorders; CI, confidence interval; RR, risk ratio.
* = p < 0.05, ** = p < 0.01, *** = p < 0.001.
Cases born in 1991–2005, diagnosed with ADHD in 1995–2011, full siblings born in 1981–2007, diagnosed in 1981–2013.
Adjusted for sex, birth date, and birth place.
Adjusted for sex, birth date, birth place, birth year of siblings, maternal and paternal age, paternal immigrant status, maternal parity, and socioeconomic status.
Adjusted for sex, birth date, birth place, birth year of siblings, maternal and paternal age, maternal and paternal psychiatric disorder, paternal immigrant status, maternal parity, and socioeconomic status.