Table 2.

Descriptive statistics for categorical variables of the ABCD cohort at baseline.

Variable	Full ABCD sample ($n=\mathrm{10,783}$)	Female-only ABCD sample ($n=\mathrm{5,122}$)	Male-only ABCD sample ($n=\mathrm{5,661}$)
	$n$ (%)	$n$ (%)	$n$ (%)
Sex
Female	5,122 (48%)	5,122 (100%)	0 (0%)
Male	5,661 (52%)	0 (0%)	5,661 (100%)
Race/ethnicity
Hispanic	2,171 (20%)	1,039 (20%)	1,132 (20%)
Black	1,536 (14%)	765 (15%)	771 (14%)
White	5,712 (53%)	2,654 (52%)	3,058 (54%)
Asian	236 (2%)	124 (2%)	112 (2%)
Multiracial	1,126 (10%)	539 (11%)	587 (10%)
Missing	2 ($<1\%$)	1 ($<1\%$)	1 ($<1\%$)
Parent marital status
Not married	3,348 (31%)	1,635 (32%)	1,713 (30%)
Married	7,353 (68%)	3,453 (67%)	3,900 (69%)
Missing	82 (1%)	34 (1%)	48 (1%)
Parent max. education
Did not complete high school/GED	509 (5%)	264 (5%)	245 (4%)
Completed high school/GED	986 (9%)	464 (9%)	522 (9%)
Some college	1,350 (12%)	622 (12%)	728 (13%)
Completed Associate’s degree	1,417 (13%)	667 (13%)	750 (13%)
Completed Bachelor’s degree	2,771 (26%)	1,302 (25%)	1,469 (26%)
Completed graduate degree	3,727 (35%)	1,795 (35%)	1,932 (34%)
Missing	23 ($<1\%$)	8 ($<1\%$)	15 ($<1\%$)
Parental income (USD)
$<\$\mathrm{25,000}$	1,435 (13%)	668 (13%)	767 (14%)
$\$\mathrm{25,000}–\$\mathrm{49,999}$	1,413 (13%)	704 (14%)	709 (13%)
$\$\mathrm{50,000}–\$\mathrm{74,999}$	1,371 (13%)	642 (13%)	729 (13%)
$\$\mathrm{75,000}–\$\mathrm{99,999}$	1,443 (13%)	696 (14%)	747 (13%)
$\$\mathrm{100,000}–\$\mathrm{199,999}$	3,077 (29%)	1,443 (28%)	1,634 (29%)
$\$\mathrm{200,000}$ or greater	1,144 (11%)	549 (11%)	595 (11%)
Missing	900 (8%)	420 (8%)	480 (8%)

Note: ABCD, Adolescent Brain and Cognitive Development Study; CBCL, Child Behavior Checklist; GED, general education diploma; Max, maximum value; Mdn, median value; Min, minimum value; $n$ (%), number of participants and percentage of sample with nonmissing data; PM, particulate matter; ${\mathrm{PM}}_{2.5}$, fine particulate matter with aerodynamic diameter $\le 2.5\mathrm{\mu }\mathrm{m}$; ${\mathrm{PM}}_{2.5}$ avg., annual average of ${\mathrm{PM}}_{2.5}$ air pollution at participants’ home address in 2016 (${\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$); ${\mathrm{PM}}_{2.5}$ Days US EPA, number of days in 2016 with ${\mathrm{PM}}_{2.5}$ levels at participants’ home address above US Environmental Protection Agency standards for ambient ${\mathrm{PM}}_{2.5}$ ($>35{\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$); ${\mathrm{PM}}_{2.5}$ max, maximum daily level of ${\mathrm{PM}}_{2.5}$ at participants’ home address during 2016 (${\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$); SD, standard deviation; USD, United States dollars.