Table 2 Clinical characteristics. N = 578

Age when ADHD diagnose was attained

 0–12

16.3%

 13–19

12.1%

  ≥ 20

69.2%

 Unknown

2.4%

 ≥ 1 biological parent with SUD

 Yes

44.8%

 No

44.6%

 Unknown

10.5%

Moderate to severe SUD:

 Alcohol

54.2%

 Cannabis

33.2%

 Hallucinogens

2.4%

 Inhalants

3.1%

 Opioids

14.5%

 Stimulants

43.6%

 Sedatives/hypnotics/anxiolytics

9.4%

 Tobacco

63.5%

Multiple SUDs (tobacco not included)

  ≥ 2 co-current SUDs (moderate to severe)

46.9%

  ≥ 3 co-current SUDs (moderate to severe)

14.0%

Psychiatric co-morbidity (other than ADHD/SUD)

 Yes

61.4%

 No

36.0%

 Unknown

2.6%

 Antisocial personality disorder

2.2%

 Anxiety disorders

5.5%

 Autism spectrum disorder

6.1%

 Bipolar and related disorders

4.3%

 Borderline personality disorder

10.2%

 Depressive disorders

31.5%

 Disruptive, impulse-control, and conduct disorders

2.4%

 Dissociative disorders

0.5%

 Feeding and eating disorders

1.7%

 Intellectual disability

2.2%

 Motor disorder (e.g., Tourette's)

0.7%

 Obsessive–compulsive and related disorders

2.1%

 Schizophrenia spectrum and other psychotic disorders

1.7%

 Somatic symptom and related disorders

1.2%

 Trauma- and stressor-related disorders (e.g., PTSD)

12.1%