Abstract
Performances of patients diagnosed with psychosis or substance abuse disorder were evaluated using the Halstead-Reitan Neuropsychological Test Battery (Reitan & Wolfson, 1993) and the General Neuropsychological Deficit Scale (GNDS). Half of the participants in each group had a documented head injury that required medical attention. Differences between patient groups with head injury was not significantly above those without head injury on the Halstead-Reitan subtests or the GNDS. Average performance in all 4 groups was in the mild to moderate impairment range according to established norms and, depending on the group, with 80% to 93% of patients scoring above the accepted cutoff for impairment on the GNDS. This study has implications for referrals attempting to distinguish head injury effects from those of psychosis or substance abuse. The GNDS did not statistically differentiate head injury effects but in these populations did detect neurological impairment, which supports the utility of this index as an indicator of overall neurological impairment.