Does addiction skip a generation? Patterns of intergenerational transmission of substance abuse

Purpose Familial aggregation of substance abuse (SA) is well-documented in epidemiological literature, yet the specific transmission patterns across multiple generations remain unclear. This study aimed to elucidate the trajectories of SA continuity across three generations, focusing on whether it persists directly through SA or manifests as other forms of psychopathology in the intermediate generation. Methods This prospective multigenerational cohort study (n = 29,115) included individuals born in Stockholm in 1953, their parents, and their children, followed through register linkages until 2016. Linear probability modeling assessed whether parental SA and psychopathology mediate and/or moderate the relationship between grandparental and grandchild SA. Results In the absence of grandparental SA, the probability of grandchildren having SA followed a gradient based on parental profiles: 7.1% with no parental SA or psychopathology, 12.8% with parental psychopathology, 17.5% with parental SA, and 22.1% with both. However, in the presence of grandparental SA, grandchild SA rates remained consistent across all problematic parental profiles (25.0%, 24.2%, and 25.9%, respectively). Notably, the most substantial increase in SA occurred in the third generation when parents had only psychiatric disorders (25.0% versus 12.8% without grandparental SA). Conclusion The study suggests that grandparental SA significantly elevates the risk of SA in grandchildren and is partially mediated and moderated by both parental SA and psychopathology. These findings underscore the importance of considering alternative pathways of SA transmission for understanding and preventing its continuity across generations.