Psychopathology, Genetic Transmission of

Complexity of Studying the Intergenerational Transmission of Psychopathology

Although it appears intuitive that parental depression may be associated with offspring psychopathology due to the environmental context, there are other equally plausible alternative explanations for the association. One such explanation is selection factors, or third (confounding) variables, that influence both the parent and offspring generations and account for the association between the two. Historically, two main approaches have been used to investigate selection factors. First, studies have “matched” cases (samples of parents with and without psychological problems) on a number of variables thought to be possible selection factors, such as socioeconomic status, race, age, and other measured variables. Second, researchers have included as many measured selection factors as possible in their analyses of the effects of parental psychopathology to statistically “control for” selection factors. Regardless of the approach, it is difficult to know whether a study has included every salient selection factor.

Additionally, it is crucial to account for genetic factors in studies of intergenerational associations because biological parents provide the environmental context and transmit their genes to their offspring. Thus, parent-offspring associations may be due to environmental factors associated with parental psychopathology and/or genetic factors that contribute to the disorder—in both generations. Thus, it is difficult to tease apart environmental factors from genetic factors that contribute to intergenerational associations. This is supported by many genetically informed studies that have documented that environmental and genetic factors are correlated. One type of genetic confound that can be problematic when studying the inter-generational transmission of psychopathology is passive gene-environmental correlation (rGE), which occurs when the same genetic factors underlying parental traits or behaviors (e.g., environmental risk factors) also influence child outcomes (e.g., depression). Although the presence of rGE renders most traditional family research uninter-pretable, researchers have historically ignored the possible role of genetic factors when studying the effects of parental psychopathology.

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