I suppose we should probably encourage most deficient people to avoid childbearing. People with heart conditions, higher than averages chances of developing cancer, ugliness (some evolutionary biologists believe it can be measured), etc.
Mental health conditions are not necessarily genetic. Certain conditions are more likely to be passed along as predispositions, other are thought to be environmental.
Depression may have genetic linkages, Schizophrenia as well (although the jury's still out about exactly how, when, why)
Anxiety disorders are more likely to be environmental. At least according to the information I've found.
In any case, all of these conditions are treatable, and don't have to lead to low a low quality of life, just like physical ailments.
I get a little bit frightened when people discuss eugenics. Darwinian logic falls apart at the generational level. We cannot breed a better human being.
People should decide to have children, based upon their desire to do so.
We cannot limit, or suggest limitations to such a basic human right.
If we do, what are other reasons for deciding that some people can and others cannot have families?
Perhaps unmarried women shouldn't be allowed to have children. Many studies indicate that children born into single-parent families are more likely to face a wide range of socio-economic difficulties that may lead to a lower quality of life.
On that basis, perhaps poor people shouldn't have children. If you assume that quality of life is measurable across demographic boundaries, than surely people who live below the poverty line are measurably less likely to have good lives than the rich.
Maybe we should encourage minorities to stop bearing children. Surely there are barriers facing these communities not faced by the white majority. How can we allow future generations of Hispanic, Black or Aboriginal children to face the challenge of living in a society that obviously limits their options.
Long story short. Not your choice and not mine. Thank the good lord