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. Author manuscript; available in PMC: 2014 Jul 15.
Published in final edited form as: Depress Anxiety. 2013 Jan 24;30(3):259–266. doi: 10.1002/da.22038

Figure 1.

Figure 1

Diagram illustrating additive genetic effects for twin 1 and twin 2. This model also applies to common, shared (C) and unique (E) environmental factors. Path “a21” reflects the additive genetic contribution of the pre-CO2 VASA score on the post-CO2 VASA score whereas path “a22” represents new/unique genetic effects associated with the post-CO2 VASA score.