Antidepressant Switching as a Proxy Phenotype for Drug Nonresponse: Investigating Clinical, Demographic, and Genetic Characteristics

Summary

This study examined why some people don’t respond well to common antidepressant medications called SSRIs. Researchers used prescription records from over 38,000 people to identify those who switched to different antidepressants as a sign of poor response. They found that people with higher education and income were less likely to switch medications, and that genetic factors influenced who responded poorly to treatment. The research demonstrates that switching medications can serve as a reliable marker for identifying nonresponders, potentially helping doctors personalize antidepressant prescribing in the future.

Background

Selective serotonin reuptake inhibitors (SSRIs) are first-line therapy for major depressive disorder (MDD), but treatment response rates are low. Clinical trials lack sufficient power to study genetic contributions to SSRI response. Electronic health records (EHRs) provide larger sample sizes needed for genetic studies but require novel response phenotypes.

Objective

To define SSRI switching as a proxy phenotype for antidepressant nonresponse and investigate its clinical, demographic, and genetic characteristics in population-based biobanks with EHR data.

Results

5,133 SSRI switchers (13.2%) and 33,680 nonswitchers were identified with median time to switch of 28 days. Higher income and education were associated with lower switching rates. Polygenic score for nonremission predicted increased switching risk. SNP-based heritability was approximately 4% on the observed scale, independent of MDD genetics.

Conclusion

SSRI switching serves as a scalable proxy phenotype for antidepressant nonresponse in EHRs, capturing demographic and genetic dimensions of treatment response that are distinct from MDD susceptibility genetics, enabling larger-scale pharmacogenetic research.
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