Beyond the heritability of life satisfaction – The roles of personality and twin-specific influences

• We examined life satisfaction and personality in an extended twin design.
• Focus on shared environmental influences and twin specific effects.
• Importance of social comparison processes for life satisfaction evaluations.
• Results showed different sources of environmental effects for twins and non-twins.
• Heritability of life satisfaction was completely shared with personality.

In a behavior genetic design, we investigated individual differences in life satisfaction and its relation to personality with respect to both internal and external influences. We questioned the absence of shared environment and examined the specific contribution of additive and non-additive genetic influences. We also tested for twin-specific environmental influences in a total sample of 1308 dyads including identical and fraternal twins, siblings, mother–child and grandparent–child pairs. The results showed substantial shared environmental influences on life satisfaction that varied between twins and non-twins, supporting twin-specific environmental influences. Additive and non-additive genetic influences on life satisfaction were completely shared with personality. The remaining variance could be explained by unique non-shared environmental influences for life satisfaction independent of personality.