Table 4.

Age in years of first use of primary problem substance by sex, sexual orientation, and each specific primary problem substance, and results of multiple regression analyses using sexual orientation to predict age of first use of primary problem substance (separate analyses by sex, adjusted for age, race, ethnicity, and initial treatment episode)

	Male Participants					Female Participants
	Heterosexual M (SD)	Gay M (SD)		Bisexual M (SD)		Heterosexual M (SD)	Lesbian M (SD)		Bisexual M (SD)
	reference	B	p	B	p	reference	B	p	B	p
Age of first primary problem use for all primary problem substances	18.55 (9.03)	23.16 (9.99)		19.90 (9.40)		17.97 (9.87)	18.56 (8.73)		17.73 (8.72)
		4.52*	<.001	1.03	.081		0.48	.452	0.36	.497
Age of first alcohol use when alcohol is the primary problem substance	14.83 (5.07)	15.57 (5.70)		14.38 (7.28)		15.69 (6.57)	13.16 (5.36)		14.10 (7.70)
		1.07	.005	−.04	.956		−1.67	.089	−1.36	.118
Age of first cocaine use when cocaine is the primary problem substance	22.78 (9.09)	26.91 (10.01)		24.17 (10.09)		23.31 (8.61)	22.89 (7.93)		21.48 (7.56)
		3.63*	<.001	0.72	.561		−0.15	.899	−0.51	.607
Age of first heroin use when heroin is the primary problem substance	21.16 (7.92)	23.34 (7.88)		20.80 (7.21)		21.95 (7.67)	20.62 (6.38)		20.44 (7.04)
		2.54	.007	−.115	.916		−1.90	.096	−0.49	.620
Age of first marijuana use when marijuana is primary problem substance	14.10 (5.02)	17.43 (5.05)		12.64 (6.44)		13.39 (4.88)	15.44 (5.64)		13.00 (2.20)
		1.98	.018	−2.18	.136		1.55	.295	−0.39	.674
Age of first methamphetamine use when methamphetamine is primary problem substance	22.02 (8.60)	27.35 (8.72)		23.65 (8.76)		20.09 (7.42)	22.41 (5.15)		20.42 (7.74)
		4.67*	<.001	1.13	.347		0.80	.593	0.18	.870

^*B met the p<.001 criterion