Premorbid adjustment in schizophrenia--an important aspect of phenotype definition.

Schizophrenia is a heterogeneous disorder, and early signs of disorder such as poor premorbid adjustment (PMA) are often present before the onset of diagnosable illness. Differences in PMA between patients may be suggestive of differing aetiological pathways. Poor PMA in schizophrenia has repeatedly been reported to be associated with male sex, earlier age at onset, illness severity, negative symptoms, and poor outcome. Studies of schizophrenia patients systematically assessed for PMA have used small patient samples and have rarely used controls.