I must be Frank & Ernest: I'm not at all confident that anyone like Barclay could've even been born in the 24th Century. I see would-be mothers, mostly, using artificial incubation instead of becoming pregnant, themselves. Genetic Engineering is, of course, not used, at least not extensively, in STAR TREK, unless it's to make the case for not using it. But if someone like Barclay could even be conceived, the tremendous likelihood is that he would be modified through STAR TREK medicine to correct for his deficiencies. By adjusting his Neural Peptides ... keeping his electrolytes balanced ... hormone therapy of the future ... all of that good stuff. By his first year, most of his Barclayness would've been screened out, so that he would be more robust, shall we say. Not that this would've turned him into another Riker, but just that he would've been given the best chance for success in Life, by not being burdened with the issues he eventually surrendered to and personified.