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. Author manuscript; available in PMC: 2008 Jul 1.
Published in final edited form as: Prev Med. 2007 May 10;45(1):31–34. doi: 10.1016/j.ypmed.2007.04.012

Table 1.

Description of covariates included in analysis of adolescent/young adult women from the baseline interviews (I) and questionnaires (Q) of 1,065 participants of the Missouri Adolescent Female Twin Study

Covariate Description Response Source
Zygosity Member of an identical or fraternal twin pair 1=MZ* I
Age Under 24 years of age at follow-up 1= under 24* I
African-American Racial Affiliation 1=African-American* I
Perceived Peer Influences Domain
Perceived Peer Alcohol Use Close friends use alcohol 1=Yes* I/Q
Perceived Peer Cigarette Use Close friends smoke cigarettes 1=Yes* I/Q
Perceived Peer Cannabis Use Close friends use cannabis 1=Yes* I/Q
Perceived Peer Other Illicit Drug Use Close friends use cocaine, stimulants, sedatives, opiates, hallucinogens, inhalants? 1=Yes* Q
Perceived Peer Attitude - Alcohol Sum of 3 items on how the participant thought their close friends felt (or would feel) about experimentation with, weekly and daily alcohol use. 2=Don't Disapprove,
1=Disapprove,
0=StronglyDisapprove		 Q
Perceived Peer Attitude - Cigarettes Sum of 2 items on how the participant thought their close friends felt (or would feel) about experimentation or heavy cigarette smoking. 2=Don't Disapprove,
1=Disapprove,
0=StronglyDisapprove		 Q
Perceived Peer Attitude - Cannabis Sum of 3 items on how the participant thought their close friends felt (or would feel) about experimentation with, occasional and regular use of cannabis. 2=Don't Disapprove,
1=Disapprove,
0=StronglyDisapprove		 Q
Perceived Peer Attitude - Cocaine Sum of 2 items on how the participant thought their close friends felt (or would feel) about experimentation with and occasional use of cocaine 2=Don't Disapprove,
1=Disapprove,
0=StronglyDisapprove		 Q
Peer Closeness Would depend on their friends most (relative to their parents) when making a serious decision about their life 1=Friends* Q
Perceived Parental Influences Domain
Perceived Parental Attitude towards cannabis Single item on how the participant thought their parents would feel/felt about cannabis use 0=Disapprove
1= Don't Disapprove* 		Q
Perceived Strictness Was mother/father more strict than most others at ages 6-13 years Yes/No* I
Perceived parental pressure regarding schoolwork Did mother/father put too much pressure on you to do well in school at ages 6-13 years Yes/No* I
Perceived consistency of rules Were mother/father pretty consistent about rules at ages 6-13 years Yes/No* I
Parental Closeness Closeness to mother/father 1=very/somewhat*
0=not very/not at all		 I
Individual Influences Domain
Academic Achievement A's and B's (with some C's) in the past school year 1=Yes* I
Perceived Health Effects of Cannabis Use How much of an effect can daily use of cannabis have on the health of people your age 0= Serious Effect
1=Mild/No effect* 		Q
Alcohol Use at baseline Had a full drink of alcohol 1=Yes* I
Cigarette use at baseline Smoked a cigarette, even a puff 1=Yes* I
Conduct Disorder DSM-IV conduct disorder without clustering (American Psychiatric Association, 1994) 1=diagnosis* I
Deviance Summary score of 9 items on how wrong the participant felt it was to do certain things, such as shoplift, lie, skip class, hit someone etc. 0=Very Wrong to
3=Not Wrong		 Q
Novelty-Seeking Summary score from 17 items from the Tridimensional Personality Questionnaire (Cloninger, 1987) 1=True, 0=False Q
Major Depressive Disorder DSM-IV major depressive disorder (American Psychiatric Association, 1994) 1=diagnosis* I

Data presented here were collected from 1994-2005 (with collection continuing for subsequent waves).

I=baseline interview, Q=questionnaire

*

Binary response categories; all others are continuous measures standardized to mean of 0 and standard deviation of 1.0