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. Author manuscript; available in PMC: 2011 Oct 1.
Published in final edited form as: Addiction. 2010 Oct;105(10):1844–1853. doi: 10.1111/j.1360-0443.2010.02993.x

Figure 1.

Figure 1

The correlated influences (Panel A), moderating influences (Panel B) and joint correlation-moderating influence (Panel C) twin models used to test the relationship between peer substance involvement (PSI) and regular substance involvement (RSI). For Panel C, while moderation of only additive genetic (A) influences is shown, C (shared environment) and E (non-shared environment) were similarly overlapping and moderated by PSI. For instance, total shared environmental influences on RSI were represented by (C21+Y1*PSI)2 + (C22+Y2*PSI)2.