Schizophrenia is a multifaceted disorder that manifests by both genetic and environmental factors. A plethora of twin and adoption studies suggest major genetic influences on the pathogenesis of schizophrenia; however, a MZ concordance of 50% also suggests environmental factors (Cardno et al., 1999). [Note, a concordance of 100%, or absolute probability that both "identical" twins are afflicted or not, would suggest a single gene disorder, as in sickle cell anemia and cystic fibrosis.] These family studies reveal that schizophrenia is a complex genetic disorder, akin to diabetes and most cancers, where not but multiple causative genes contribute to susceptibility — a polygenetic disease. Moreover, there are presumably environmental factors that contribute to the onset.

An emerging vulnerability-stress-coping model attempts to frame psychotic and affective disorders based on a biopsychosocial perspective (Nuechterlein & Dawson, 1984; Nuechterlein et al., 1994; Yank, Bentley, & Hargrove, 1993). Vulnerabilities may predispose individuals for the disorder, while environmental stressors can potentially modulate (trigger) the expression of symptoms in vulnerable bodies and minds.

The vulnerability-stress-coping model.

In schizophrenia, vulnerability may include genetic predisposition, birthing complications, and CNS viral infections. Stressful life events (e.g. being fired from work, terminating a relationship, or moving to a foreign environment) and biological stressors (e.g. substance abuse) may exacerbate the illness by triggering the emergence or reoccurrence of symptoms. However, protective coping mechanisms may safeguard vulnerable persons by weakening or eliminating symptoms.

The vulnerability-stress-coping model demonstrates the composite mechanism of schizophrenia and provides a useful diagram for optimal combination therapy for clinical management.

References

Cardno, A. G., Marshall, E. J., Coid, B., Macdonald, A. M., Ribchester, T. R., Davies, N. J., et al. (1999). Heritability estimates for psychotic disorders: the Maudsley twin psychosis series. Arch Gen Psychiatry, 56(2), 162-168.Nuechterlein, K. H., & Dawson, M. E. (1984). A heuristic vulnerability/stress model of schizophrenic episodes. Schizophr Bull, 10(2), 300-312.

Nuechterlein, K. H., Dawson, M. E., Ventura, J., Gitlin, M., Subotnik, K. L., Snyder, K. S., et al. (1994). The vulnerability/stress model of schizophrenic relapse: a longitudinal study. Acta Psychiatr Scand Suppl, 382, 58-64.

Yank, G. R., Bentley, K. J., & Hargrove, D. S. (1993). The vulnerability-stress model of schizophrenia: advances in psychosocial treatment. Am J Orthopsychiatry, 63(1), 55-69.