An extended Swedish study on the adoption of anxiety disorder and its intergenerational family relationship with major depression

Objective:

To clarify, using an extended adoption design, the sources of parent-child transmission of anxiety disorder (AD) and its major subforms and their intergenerational familial relationship with major depression (MD).

Methods :

The descendants (born between 1960 and 1992) and their parents, from six types of families (intact, not living with the biological father or mother, living with the stepfather or stepmother and adoptive), were determined from Swedish national samples. Diagnoses were obtained from national medical registries. We assessed three sources of parent-offspring resemblance: genes plus breeding, genes only, and breeding only. To test the effects of comorbidity, unique diagnoses were assigned to comorbid cases based on frequency and recency.

Results:

For parent-child transmission from Alzheimer’s disease to Alzheimer’s disease, the best estimate of the tetrachoric correlations for the three types of parent-offspring relationships, genes plus breeding, genes only, and breeding only, equals +0, 16 (95% CI = 0.16, 0.16), +0.12 (95% CI = 0.10, 0.13) and +0.06 (95% CI = 0.04, 0 .07), respectively, with broadly similar results for DM-to-DM transmission. Correlations between disorders and generations were slightly weaker, with genetic and breeding correlations for AD and DM estimated at +0.83 (95% CI = 0.76, 0.90) and +0 .83 (95% CI = 0.69, 0.96), respectively. Analyzes of panic disorder and generalized anxiety disorder (GAD) produced comparable results, with the genetic correlation with DM being slightly higher for generalized anxiety disorder than for panic disorder. Applying a diagnostic hierarchy to comorbid cases resulted in a decrease in intergenerational transmission of crossover disorders with an estimated genetic correlation equal to +0.46 (95% CI = 0.30, 0.62).

Conclusions and relevance:

For AD and its major subforms, intergenerational transmission includes both genetic and herding effects. In traditional analyses, AD and MD demonstrate highly correlated genetic and breeding effects. The genetic correlation weakened when applying a diagnostic hierarchy.

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