Metabolic compensation appears possible within the serotonergic, folate, purine system and it seems possible that clinical illness may result when the system can no longer compensate. For example, elevated serotonin, induced by stress accumulation of tryptophan, could be compensated by a lowered folate ratio, normalizing the beta-carboline index and preventing hallucinations. Conversely, deficient serotonin, induced by a psychological loss or transport deficit, could be compensated by raising the folate ratio, which would normalize the beta-carboline index and prevent further depression. Increased purine turnover would seemingly lower the folate ratio, compensating perhaps for hallucinatory activity or mania. Several genetic defects of enzymes or transport proteins could seemingly preclude normal compensations within the system.