Moeburn, please call a pharmacist to confirm this if you don't believe me. Someone's given you some incorrect information or you have some drug names confused. I easily confirmed this with two pharmacology books and with my medical school pharmacology reference sites.

Benadry is only an antihistamine and has nothing to do with the class of drugs called selective serotonin reuptake inhibitors. Benadryl/diphehydramine has been around for much longer than SSRIs and works in a completely different way from those antidepressants. It's much safer to take, in fact.
http://www.medicinenet.com/diphenhydramine/article.htm

SSRI antidepressants are relatively new when compared to Benadryl. They include Prozac, Paxil, Zoloft, Effexor, Celexa, and Cymbalta. Several of these can indeed be hard to stop taking. But trust me. Benadryl isn't one of these. Any physician or pharmicist will confirm this for you. The link below will show you both the brand names and chemical names for these drugs, some of which end in -ine just like diphendyramine, which may be why you think they belong to the same class of drugs.
http://mentalhealth.about.com/cs/psy...gy/a/ssris.htm

It's true that 5-HTP is a precursor to serotonin.