Laboratory studies suggest that antidepressants affect the risk of some cancers, including colorectal cancer. To investigate whether selective serotonin reuptake inhibitors (SSRIs) and tricyclic antidepressants (TCAs) are associated with colorectal cancer risk, we conducted a case-control study among enrollees of an integrated healthcare delivery system in Washington State. Cases were first diagnosed with invasive colorectal cancer between 2000 and 2003; controls were randomly selected from Group Health enrollees and matched to cases on age, sex and length of enrollment before diagnosis/reference date. We used logistic regression to estimate odds ratios (OR) and 95% confidence intervals (CI) for colorectal cancer in relation to use of any antidepressant, SSRIs only or TCAs only, among 649 cases and 656 controls. Use of any antidepressant was associated with a reduced risk of colorectal cancer (OR = 0.7, 95% CI = 0.5-0.9). Associations were similar for persons who used SSRIs exclusively (OR = 0.7, 95% CI = 0.4-1.1) and TCAs exclusively (OR = 0.7, 95% CI = 0.5-1.2); however, this reduction in risk appeared limited to persons without a prior cancer at another site. Our data support findings from previous epidemiologic and animal studies that suggest antidepressants may reduce the risk of colorectal cancer. Future studies with larger sample sizes should further examine individual drugs as well as dose, duration and recency of use.
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