[the_fonz]

I wonder about the causal link/s. Speculating, maybe less stressed/anxious/depressed and healthier people have more fun, better genes or have more resources to have better healthcare? Also, less stressed mothers seem inherently more likely to bring a child to term than a stressed mom-to-be because IIRC stress induces both labor or spontaneous abortion. Maybe there's a MHC or other immune component that leads to stronger attraction and/or healthier babies? There was a dating startup in the late 90's that promised to match people on MHC, but I'm not sure how far they got on that.... maybe AI/deep learning trained on a big enough SNPs samples and qualitative mutual attractiveness rating could tackle it these days.