2005 2005 2005 2004 2002 1982 2005 2002 2003 2000 1999 2000 2001 1999 2003 2005 1991 1997 1999 1991 2005 2001 2005 2005 1997 1998 2002 2003 1995 2001 2003 2002 2000 2003 1 1999 2005 1999 1998 Fig. 1 Note: i p  Method Sample 2002 in press 1975 1966 2001 2000 1996 2004 SD SD  n n t P  Measures Conduct problems 1997 1999 1994 2003 2004 either r P  1997 Marijuana use 1997 Statistical analysis 1997 1 2005 2006 1 2 2 2 1997 2006 \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym} 
\usepackage{amsfonts} 
\usepackage{amssymb} 
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}
$$ t_{i} {\text{ }} = {\text{ }}t{\text{ }} + {\text{ age}}_{i} t_{a} $$\end{document} t t a i i 2006 1997 Results SD  2 P  F P  SD  SD  t P  F P  2004 SE  SE  t P  SE  SE  t P  SE  SE  t P  SE  SE  t P  2005 P  R 2    r =  r =  1996 r r r r r r The relationship between the liability to initiation and progression of conduct problems and marijuana use 1 Table 1 CCC model tests for conduct problems and marijuana use  Initiation   Progression  2 2 2 β 2 2 2 Time 1 Conduct problems 0.69 (0.41, 0.86) 0.08 (0.02, 0.32) 0.22 (0.14, 0.32) 0.74 (0.22, 0.95) 0.00 (0.00, 0.00) 0.27 (0.00, 0.37) 0.73 (0.05, 0.76) (0.41, 0.86) (0.02, 0.32) (0.14, 0.32) (0.22, 0.95) (0.00, 0.00) (0.00, 0.37) (0.05, 0.76) Time 2 Marijuana use 0.35 (0.05, 0.63) 0.47 (0.24, 0.71) 0.18 (0.10, 0.36) 0.88 (0.38, 0.99) 0.64 (0.00, 0.65) 0.00 (0.00, 0.00) 0.36 (0.00, 0.48) (0.05, 0.63) (0.24, 0.71) (0.10, 0.36) (0.38, 0.99) (0.00, 0.65) (0.00, 0.00) (0.00, 0.48) Conduct problems 2  df P  2  df P  Marijuana use 2  df P  Multivariate analyses 2 Fig. 2 Note: i p  2 2  df P  2  df P  Table 2 Multivariate model fitting for relations between conduct problems and marijuana use Estimated model Beta coefficient set at zero -2LL df 2 Model 1-Full theoretical model – 5433.945 5124 – Model 2 β 2 1 5438.720 5125 4.78* Model 3 β 3 1 5436.969 5125 3.02 Model 4 β 4 1 5433.847 5125 0.10 Model 5 β 3 2 5433.771 5125 0.17 Model 6 β 4 2 5433.825 5125 0.12 Model 7 β 4 3 5442.258 5125 8.31** Note P P Discussion This study is among the first to investigate the relationship between the initiation and progression dimensions of substance use with an adolescent twin sample and highlights that the initiation and progression of marijuana use, although strongly related, cannot be assumed to have a single liability of risk. The findings of this study also provide insight into the relationship between conduct problems and adolescent substance use. Specifically, the results indicate that in a UK sample, the longitudinal association between the liability to conduct problems during childhood and early adolescence and the liability to initiate and progress marijuana use in adolescence and early adulthood are not strongly related. Thus, other risk factors and the mechanisms through which they exert effects on the initiation and progression of marijuana use in adolescence should also be investigated. 2005 1997 1998 1999 1999 2005 2005 1 2001 2003 2003 P  2006 2006 2005 2003 2001 2002 2003