If they find it it will have a side effect like being unable to enjoy sports or orgasms any more and to get fat with close to no food (grin).

For the serious part: In order to be effective independent of environmental influences on the emotional make-up it has to be a pretty strong intervention that would change us more than I'd like to see.
If it's a small intervention it is unlikely to 'overrule' the influence of our experiences on our emotion.

The approach to change the environment (experiences etc.) is here the much better one in my eyes.

Wolfgang (who in other contexts may say yes to genetic engineering)