Review Of: Shoval G et al, Depress Anxiety 2019;36(10):921–929

Many cancer patients experience depression, especially those with poor prognoses. Compared with euthymic patients, depressed cancer patients are less adherent to their cytotoxic medications, and this poor adherence can worsen their long-term survival. Yet surprisingly, some studies have reported a higher mortality rate among cancer patients taking antidepressants—but might confounding factors account for this finding (eg, patients with worse prognoses are more likely to be depressed and therefore to be placed on antidepressants)?

This large (n = 42,075) retrospective cohort study controlled for several confounding factors to get a better understanding of the relationship between antidepressant use and mortality. Using an Israeli national health services database, the authors extracted data on patients who were diagnosed with cancer and purchased an antidepressant prescription within the 4-year study period (2008–2012). Patients were further divided into subgroups based on antidepressant adherence, ranging from non-adherent to highly adherent. Adherence was defined as the number of months with actual filled prescriptions divided by the number of months when an antidepressant was prescribed.

An initial analysis indicated an increase in mortality with antidepressant adherence, but also revealed that older and sicker patients tended to be the most adherent, leading to an over-representation of mortality in the adherent group.

A subsequent analysis, adjusting for such factors, showed the opposite: Patients who were adherent to their antidepressant lived significantly longer than patients who were minimally adherent (< 20% adherent) or non-adherent. The mortality rate among patients with the highest antidepressant adherence (> 80% adherent) was 20% lower, over the study period, compared to the non-adherent or minimally adherent group. Subgroup analyses showed this adherence benefit remained regardless of cancer type, including lung, prostate, breast, and colon cancer.

CHPR’s Take
This large retrospective study found that antidepressant adherence was associated with improved survival in people with cancer. Whether this is due to greater adherence to cancer treatment or some other reason remains unclear. The study should further our resolve to treat depression and anxiety in cancer patients, and to encourage patients to not miss doses of their antidepressants.