"Whether SSRIs affect "normals" is a question I avoided answering in the book. There is still no large-scale, definitive research on that topic, although leading scientists have proposed the critical studies that would settle the matter. The small studies that do come to my attention all point in one direction: these medications do have the power to affect "normals" -- people without any psychiatric diagnosis.

The study that is most on point has just come across my desk and is not yet published. Scientists at the Langley Porter Institute of the University of California (Brian Knutson {now at the National Institutes of Health}, Owen Wolkowitz, and others) looked at the social functioning of normal people -- that is, people judged to be free of mood or personality disorders -- before and after a month on an SSRI. The subjects were asked to perform a negotiating task in which they and a stranger had to approach a stressful problem. On medication, the normal subjects were less negative and more collaborative, and they tended from this posture to succeed in their negotiations; this result, the researchers suggested, resembles an effect SSRIs have in male vervet monkeys, increasing "prosocial" behaviors that can raise status in the troop hierarchy. On antidepressants, these normal subjects displayed altered personality traits, and the degree of alteration correlated with blood levels of the medication. If I were writing Listening to Prozac today, I would say that there is suggestive evidence that medications like Prozac can affect normal people, even that it can alter their social behavior -- and it may be that these effects are the rule, not the exception."

(source: Kramer, P. (1997). Listening to Prozac. Penguin: New York, pp. 320-321.)