Having a schizophrenic disorder may place an individual at much greater risk for developing a mood disorder. In fact, according to the president of the 20th Collegium Internationale Neuropsychopharmacologicum (CINP), comorbid mood disorders are so prevalent in this patient group that they may be considered a fundamental characteristic of schizophrenic disorders.

This strong relationship has been controversial, with some maintaining that mood disorder symptoms in schizophrenia are actually a manifestation of schizophrenia rather than discrete mood disorders, said Lewis Judd, M.D., during a CINP presentation, "Current Concepts of Affective Disorders in Schizophrenia,"held recently in Melbourne. To shed light on the poorly understood relationship Judd, psychiatry department chair at the University of California, San Diego, examined two major epidemiological studies, the NIMH Epidemiological Catchment Area Program (ECA) and the National Comorbidity Survey (NCS).

The earlier NIMH study had identified schizophrenia's lifetime prevalence as 1.5% (34 individuals, ages 18 to 65 years, out of a cohort of 20,291). Surprisingly, according to Judd, 91% of schizophrenia was accompanied by mental or substance abuse disorders.

With an odds ratio of 10 considered a strong comorbid association, the ratio of 14 for schizophrenia to be comorbid with unipolar disorders and 46 for bipolar disorder denote a strong, highly significant association between schizophrenia and mood disorders.

A more recent (1995) NCS, with 8,098 individuals, showed a lower lifetime prevalence for schizophrenic disorders of 0.82%. Among the 66 identified individuals with schizophrenic disorder (nonaffective psychosis), only 18.6% were without comorbid mood disorders. Analysis showed 59% to have comorbid lifetime diagnosis of unipolar disorder. Judd pointed out that because of the high prevalence of unipolar disorder in the general population, the odds ratio of 4 (times greater risk than for nonschizophrenia disorder patients), although statistically significant, is a weak association. The odds ratio for comorbid bipolar disorder (found in 22% of all schizophrenics), however, is 9. "This approaches the gold standard of 10, indicating again a very strong association,"Judd stated.

Judd's epidemiological investigation into comorbid mood disorders in schizophrenia revealed a severe influence on outcome. In the overall cohort of patients with schizophrenic disorder, 37% made at least one suicide attempt (as compared with 7.9% in the general nonschizophrenic population) (p<0.0001, highly significant).

Schizophrenia, Judd noted, has the highest suicide rate of any mental disorder. For individuals in the NCS cohort with schizophrenia and at least one lifetime comorbid mood disorder, the suicide rate (attempted) was 40.4% as compared with <1.0% for those with schizophrenia alone. For schizophrenic disorder with unipolar disorder the suicide rate was 27.5% versus 10.4% for unipolar disorder alone.

Bipolar disorder, with the second-highest risk of any mental disorder for suicide attempts (28.5%), proves to be very lethal when comorbid with schizophrenia. "The 70.6% lifetime suicide attempt rate found for this group is the highest we have seen," Judd said.

Comorbid mental illness is very common and a fundamental characteristic of schizophrenic disorder," Judd went on to say, adding, "Mood disorders are by far the most common, and will be found in at least 80% of the patients." October 1996 Psychiatric Times