Researchers have identified 160 genes linked to brain shrinkage in adults. The genes appear to be involved in brain development, vascular and neurodegenerative diseases, and some psychiatric conditions.0 genes linked to brain shrinkage in adults. The genes appear to be involved in brain development, vascular and neurodegenerative diseases, and some psychiatric conditions.0 genes linked to brain shrinkage in adults. The genes appear to be involved in brain development, vascular and neurodegenerative diseases, and some psychiatric conditions.