Integration of functional aspects in the treatment of schizophrenia is important; however, little knowledge exists whether the global assessment of functioning (GAF) predicts early clinical course.

To investigate associations between GAF and relapse.

To identify all adults (≥18 years) for the first-time diagnosed with schizophrenia in Denmark in 2004-2012 and calculate the risk of 2-year relapse.

Patients were categorized according to baseline GAF-scores (at initiation of outpatient or discharge from inpatient contact, respectively): 61-100, 46-60, 31-45 and 1-30. Relapse was the first schizophrenia (re)-hospitalization. We performed Cox regression analyses (hazard rate ratios (HRR), 95%-confidence intervals (95%-CI)) adjusted for: sex, age, substance abuse, duration of untreated psychosis (DUP), length of baseline hospitalization, index-year, antipsychotic treatment and side effects.

Among 5,674 incident patients, 5,184 (91.4%) had a valid baseline GAF-score. Lower GAF-scores were associated with longer DUP and baseline hospitalization. 2,278 (40.2%) experienced relapse, 428 (20.7%) of outpatients and 1,850 (51.3%) of inpatients. Lower GAF was associated with an increased risk for relapse in a dose-response relationship. Among inpatients, GAF≤30 (compared with GAF>60) was Associated with a 43% increased risk. Among outpatients, the relapse risk increase was HRR=1.22 (95%-CI=0.76; 1.97) with GAF=46-60; HRR=1.93 (95%-CI=1.24; 3.02) with GAF=31-45, and HRR=3.07 (95%-CI=1.84; 5.13) with GAF=1-30.

Lower baseline GAF was associated with increased 2-year relapse risk in a dose-response relationship. The clinically widely used GAF may be an important tool for prediction of early clinical course among incident adult schizophrenia patients, in particular in an outpatient setting.