Symptoms of obsessive-compulsive disorder preceded symptoms of schizophrenia in 48% of 133 patients hospitalized over an 11-year period who had both disorders.

The obsessive-compulsive symptoms and psychotic symptoms occurred simultaneously in 24% of patients, and the obsessive-compulsive symptoms followed the first occurrence of psychotic symptoms in 28%. The first clinically significant symptoms of obsessive-compulsive disorder (OCD) appeared at a mean age of 19.1 years, compared with a mean age of onset of 20.4 years for first psychotic symptoms, Sarit Faragian, Ph.D., and associates reported.

The difference in age of onset of the two disorders was significant in men (who accounted for 73% of the cohort) but not in women. Also, both disorders appeared earlier in men than in women. The men first developed OCD at a mean age of 18.3 years and schizophrenic symptoms at a mean of 19.8 years. The women first developed OCD at a mean age of 21.2 years and schizophrenic symptoms at a mean of 22.1 years, reported Dr. Faragian, a researcher at Tirat Carmel (Israel) Mental Health Center.

The study included consecutive patients admitted to the center with schizo-obsessive disorder from 1999 through 2010 (Psychiatry Res. 2012;197:19-22).

A considerable gap was found, however, between the mean ages of symptom onset and that of diagnostic assessment (mean age, 30 years), so the investigators also analyzed a subgroup of 52 patients with a first episode of schizophrenia (mean age at assessment, 22 years) in order to minimize recall bias. The findings reinforced those from the larger cohort: Clinically significant OCD symptoms emerged about 3 years earlier than schizophrenia symptoms in the subgroup, at ages 18.2 and 21.6 years, respectively.

The OCD symptoms came first in 26 (50%) of the patients with first-episode schizophrenia, simultaneously in 14 patients (27%), and after schizophrenia symptoms in 12 patients (23%).

The findings imply that obsessive-compulsive symptoms are independent of psychosis and not a result of schizophrenia in a substantial proportion of patients with schizo-obsessive disorder, the investigators suggested. It’s still true, however, that antipsychotic drug treatment or unknown schizophrenia-related causes triggered secondary OCD symptoms in a subset of patients with schizophrenia, as previous studies have shown.

In the current study, the investigators also compared the 133 patients with schizo-obsessive disorder with 113 matched patients admitted during the same time period who had schizophrenia but not OCD. Symptoms appeared significantly earlier in the schizo-obsessive group (20.4 years), compared with the schizophrenia group (23.4 years).

Patients in the schizo-obsessive group were significantly more likely to report that psychotic symptoms started before age 18 (46.6%), compared with patients in the schizophrenia-only group (21.2%), or that symptoms started before age 22 (69.9% vs. 52.2%, respectively).

Because OCD symptoms started before psychotic symptoms in so many schizo-obsessive patients, OCD might be useful to identify youths at high risk for progression to schizophrenia, Dr. Faragian suggested. The same might be said of OCD and bipolar disorder, based on previous studies showing that bipolar disorder started at a younger age in patients with anxiety disorders, particularly OCD, he added.

Among other limitations to the current study, the number of women in the study might have been too small to show a significant difference in temporal onset of OCD and psychotic symptoms. Both schizophrenia and OCD are heterogeneous disorders, however, and early-onset OCD is known to be familial and more common in boys. Future studies should focus on the familial influences on age of onset of schizo-obsessive disorder, Dr. Faragian suggested.

The study appears to be the largest so far to analyze age of onset of symptoms in patients with schizo-obsessive disorder. It excluded patients with affective and organic mental disorders or drug-induced or alcohol-induced psychoses.

Dr. Faragian and colleagues have no disclosures of financial conflicts of interest to report.