Preventing inherited mental disorders may sound like an oxymoron but is already a fact. Much more will become feasible in a few years. For diseases with Mendelian inheritance patterns, family history and/or screening to detect carriers permits pre-conceptual counseling (to avoid pregnancy if abortion is rejected as an option) and pre-natal detection and abortion of affected fetuses. Thus, screening amniocentesis and abortion have reduced Tay-Sachs births in North America by more than 90%.
Neonatal screening to identify metabolic and endocrine abnormalities permits dietary or hormonal interventions to prevent neuropsychiatric abnormalities. The genotype is unchanged but the phenotype is normal or near normal. Thus, in the case of PKU prevented, the child still lacks phenylalanine hydroxylase but the provision of a low phenylalanine diet prevents damage to CNS.
However, the common mental disorders are not Mendelian in their inheritance. Though they display familial patterns, they result from interactions between multiple genes and environmental factors. The specification of the human genone, likely to be completed within the next three to five years, will accelerate identifying genes conferring risk; it will make it possible to identify environmental precipitants (viral? dietary? psychological? social?) that interact with the genotype to produce disease.The new knowledge will permit interventions tailored to individual susceptibilities to prevent psychiatric disorders.
L. Eisenberg, MD
Harvard Medical School, Boston