Table 1.

Baseline characteristics of Add Health study participants according to early drug use, 1994–2008.

Characteristics	na	%b
Race
Black	2988	20.5
White	5426	61.2
Hispanic	2768	18.3
Sex
Male	4074	38.5
Female	7120	61.5
Age (years)
11–15	7716	73.7
16–19	3455	26.3
Cigarette smoking
None	4185	75.5
1–9	677	12.7
10–19	275	5.4
≥ 20	258	6.6
Alcohol use
None	2346	23.9
2 days or once a month	805	8.2
1–5 days in past 12 months	6740	67.8
Marijuana
None	1809	76.0
1–9 times used in past month	610	24.0
Age of onset (years) of cocaine use
None	10,546	99.4
11–15	14	0.1
16–18	74	0.6
Age of onset (years) of other illicit drugsc
None	10,094	98.3
11–15	26	0.3
16–18	160	1.4
Used mental health servicesd
No	9661	85.3
Yes	1516	14.7

^aUnweighted sample distribution.

^bWeighted percentage distribution.

^cThis variable refers to the use of LSD, amphetamines or heroin and their derivatives and any other illicit more active psychoactive substance.

^dUsed of mental health services (No = nonuse of mental health services; Yes = reported using mental health services).