"Some studies suggest that possible MDMA-induced neurotoxicity to the serotonin system can be largely prevented by taking a double dose of fluoxetine (Prozac) or another SSRI shortly after starting to "come down". Post-E Prozac in particular mitigates the oxidative stress and consequent risk of serotonergic axon damage caused by reactive products of dopamine deamination. The long-acting SSRI Prozac/fluoxetine, and its even longer-acting metabolite norfluoxetine, apparently prevents the uptake of dopamine (and any toxic metabolite(s)?) into the serotonergic nerve terminals by binding to the serotonin reuptake transporter with higher affinity than MDMA or serotonin."
http://www.mdma.net/#ecstasyprotect
And...
The time course of damaging events in rats can be seen by administering SSRIs, such as fluoxetine and citalopram, after MDMA. Pretreatment with fluoxetine (Prozac) or citalopram (Celexa) has been shown to block the neurotoxicity of MDMA (Battaglia, 1988; Schmidt 1987; 1990; Shankaran, 1999a), probably by blocking interactions of MDMA with SERT. More interestingly, fluoxetine remains almost fully protective if given 3 or 4 hours after MDMA. By 4 hours, most of the MDMA-induced release of 5-HT and DA has already occurred (Gough, 1991; Hiramatsu, 1990) and increases in extracellular free radicals (Colado, 1997b; Shankaran, 1999a) and lipid peroxidation (the alteration of fat molecules by free radicals) (Colado, 1997a) can be measured. Nevertheless, the administration of fluoxetine at this point decreases subsequent extracellular oxidative stress (Shankaran, 1999a) and long-term 5-HT depletions (Schmidt, 1987; Shankaran, 1999a). Fluoxetine will still be partially protective if given 6 hours after MDMA but has no protective effect 12 hours after administration (Schmidt, 1987). This shows that neurotoxic MDMA regimens initiate a series of events that become increasingly damaging between 3 and 12 hours after drug administration in rats.
http://www.erowid.org/chemicals/mdma/mdma_neurotoxicity1.shtml#timecourse
There's been more that just one study, but it's still just a theory, and most of the research has been done on rats. We don't know a whole lot about the 'damage' ecstasy does in general. But some people see the possible safety benefits as sufficient reason to take an SSRI (especially prozac) after MDMA. Throw in the fact that they can sometimes be used to abort a roll, and there's definite potential there. It would be more of a solution for people who roll very occasionally and are just looking for possible ways to be a little safer.