W4. THE ROLE OF GENETIC SUSCEPTIBILITY IN RISKS OF PSYCHIATRIC DISORDERS AFTER A CANCER DIAGNOSIS.

The diagnosis of cancer is a life-changing and stressful experience among most patients. Indeed, previous studies have consistently shown an association between a cancer diagnosis and subsequent risk of common psychiatric disorders, including major depressive disorder, anxiety, stress-related disorders, and substance use. Yet, evidence is limited regarding the role of genetic susceptibility to psychiatric disorders on the association between cancer diagnosis and common psychiatric disorders. Thus, we aimed to assess the role of polygenic risk score (PRS) for psychiatric disorders on the association between cancer diagnosis and subsequent risk of common incident psychiatric disorders adjusting for multiple confounders. We conducted a matched cohort study of UK Biobank including 78,465 cancer patients diagnosed from January 1, 1997 to January 31, 2020 and 392,325 cancer-free individuals individually matched to the cancer patients by birth year, sex and availability of primary care records. The exposure was a first diagnosis of cancer, and the outcome was a first diagnosis of common psychiatric disorders (i.e., major depressive disorder, anxiety and stress-related disorders, or substance use) or prescription of psychotropic medications. We used flexible parametric model and Cox model to estimate the subsequent risk of common psychiatric disorders following a cancer diagnosis and performed further stratified analysis by individual genetic susceptibility (i.e., PRS for major depressive disorder or anxiety and stress-related disorders). The mean age at cancer diagnosis was 62.7. During up to 24 years of follow-up, we observed an increased risk of psychiatric disorders or prescription of psychotropic medications with a peak during the first 6 months after cancer diagnosis (hazard ratio [HR]=4.25; 95% confidence interval [CI] 3.94-4.70), which then decreased rapidly but remained statistically significant throughout the follow-up period (≥13 months: 1.22 [95%CI 1.19-1.26]). The increased risk of psychiatric disorders among cancer patients was largely similar across groups with varying PRSs for major depressive disorder, and anxiety and stress-related disorders. The distinct rise in the risk of common psychiatric disorders after cancer diagnosis seems largely independent of known genetic risk factors for these disorders. These results highlight the need for clinical surveillance of common psychiatric disorders among newly diagnosed cancer patients. [ABSTRACT FROM AUTHOR]