Table 3.

Substance use outcomes at age 17.5 in twin pairs (N=150 pairs) discordant for Early-Onset Depressive Disorders and substance use at follow-up.

	No. of pairs*	OR	95%CI
Daily Smoking	32/46	1.83	.98-3.42
Smokeless Tobacco	19/32	5.63	1.27-24.8
Drug Use	11/16	1.67	.40-6 97
Frequent Alcohol Use	14/22	3.75	1.07-13.20
Regular Drunkenness	31/56	1.43	.82-2.53

Abbreviations: CI=Confidence Intervals; OR=Odds Ratios.

^*Fraction of pairs discordant both for depressive disorder at baseline and substance use at follow-up in which the co-twin depressed at baseline was the twin who met the substance use outcome. For smokeless tobacco use, this fraction was 4 of 4 sister-sister pairs and 7 of 9 brother-brother-pairs, but only 8 of 19 sister-brother twin pairs.

The odds ratios were calculated using conditional logistic regression. The odds ratios were adjusted for sex, other covariates examined were conduct disorder, attention-deficit (ADHD), oppositional-deficit (ODD), substance use and generalized anxiety disorders, but none were significant predictors. All models excluded baseline users.