Importance: Psychiatric comorbidities are common among patients with cancer. However, whether or not there is increased risk of mental disorders during the diagnostic workup leading to a cancer diagnosis was unknown.
Objective: To examine the relative risks of depression, anxiety, substance abuse, somatoform/conversion disorder, and stress reaction/adjustment disorder during the periods before and after cancer diagnosis compared with individuals without cancer.
Design, setting, and participants: Nationwide matched cohort study from January 1, 2001, to December 31, 2010, in a Swedish population and health registers.
Main outcomes and measures: We estimated the time-varying hazard ratios (HRs) of the first clinical diagnosis of the studied mental disorders from 2 years before cancer diagnosis, through the time of diagnosis, and until 10 years after diagnosis, adjusting for age, sex, calendar period, and educational level. To assess milder mental conditions and symptoms, we further assessed the use of related psychiatric medications for patients with cancer diagnosed during 2008-2009.
Results: The study included 304 118 patients with cancer and 3 041 174 cancer-free individuals who were randomly selected from the Swedish population and individually matched to the patients with cancer on year of birth and sex. The median age at diagnosis for the patients with cancer was 69 years, and 46.9% of the patients were female. The relative rate for all studied mental disorders started to increase from 10 months before cancer diagnosis (HR, 1.1; 95% CI, 1.1-1.2), peaked during the first week after diagnosis (HR, 6.7; 95% CI, 6.1-7.4), and decreased rapidly thereafter but remained elevated 10 years after diagnosis (HR, 1.1; 95% CI, 1.1-1.2). The rate elevation was clear for all main cancers except nonmelanoma skin cancer and was stronger for cancers of poorer prognosis. Compared with cancer-free individuals, increased use of psychiatric medications was noted from 1 month before cancer diagnosis and peaked around 3 months after diagnosis among patients with cancer.
Conclusions and relevance: Patients diagnosed as having cancer had increased risks of several common mental disorders from the year before diagnosis. These findings support the existing guidelines of integrating psychological management into cancer care and further call for extended vigilance for multiple mental disorders starting from the time of the cancer diagnostic workup.