How much does family history increase your mental health risk?

Mental health conditions ‘run in families’, a common phrase that we often hear, but how much of this is true? How much is due to genetics and how much is due to the shared environments, or broader psychosocial factors?

Research shows that having a family history of a mental disorder increases the risk of developing that specific disorder. Mental health condition heritability is often assessed using relative risk measures (Kendler, 2013). For example, depression risk can be two to three times higher for individuals if they have an affected first-degree relative (Sullivan et al., 2012). This “doubling or tripling of risk” is alarming, but it is also a bit misleading.

What if a person’s baseline risk is…