Prozac linked to increased cancer growth: New research suggests that serotonin is a natural growth suppressant for some types of tumors, and that SSRI antidepressants may block that effect. Eli Lilly, the manufacturer of Prozac, of course disputes the relevance of the finding. I agree with the researchers’ caveat that this should not make anyone stop their antidepressant, which probably presents a greater risk than the theoretical research finding, which was established in the test tube and is not supported by any epidemiological findings. New Scientist

[If you know a little pharmacology, this finding may at first seem counterintuitive. SSRIs increase the amount of serotonin around by blocking its reuptake, so if serotonin is good for stopping tumor growth, why wouldn’t SSRIs enhance the effect? The answer is that it is intracellular serotonin that inhibits tumors, and the SSRIs increase extracellular serotonin by blocking its transport into cells (“reuptake”). –FmH]