. Author manuscript; available in PMC: 2011 Nov 1.

Published in final edited form as: Dev Psychopathol. 2010 Nov;22(4):831–848. doi: 10.1017/S0954579410000490

Table 2.

Phenotypic Correlations among Major Depressive Disorder (MDD) symptoms and Nicotine Dependence (NicD) Symptoms for Combined Sample and Male and Female Samples

Combined sample		NicD			MDD

		15 years	18 years	21 years	15 years	18 years	21 years
NicD	15 years
	18 years	.40^***
	21 years	.28^***	.56^***
MDD	15 years	.17^***	.08^*	.07^*
	18 years	.07	.11^**	.08^*	.24^***
	21 years	.09^**	.08^*	.11^**	.14^***	.26^***

Male/Female samples		NicD			MDD

		15 years	18 years	21 years	15 years	18 years	21 years
NicD	15 years		.37^***	.26^***	.13^*	.10	.04
	18 years	.49^***		.54^***	.03	.06	.03
	21 years	.32^***	.67^***		.04	.06	.10^**
MDD	15 years	.20^**	.15^**	.13^**		.18^*	.07
	18 years	.06	.18^***	.12^*	.27^***		.28^***
	21 years	.12^*	.12^**	.12^*	.18^***	.25^***

Notes. Male twins are above diagonal, and female twins are below diagonal. MDD=major depressive disorder. NicD=nicotine dependence.

< .05,

^**

<.01,

^***

<.001.