Attention deficit in schizophrenia may be underestimated due to limited sensitivity of attention tests. Comparing the frequency of attention deficits in schizophrenia to attention deficit hyperactivity disorder (ADHD) may solve this problem, since all subjects with ADHD should demonstrate impaired attention. Twenty-seven subjects with schizophrenia were compared to 74 clinical controls with ADHD on tests of focused/divided/sustained attention and impulsivity.
Results: The frequency of impaired attention was equal among subjects with schizophrenia and ADHD-combined (ADHD-C), while ADHD-inattentive (ADHD-I) subjects were more impaired. Half the subjects with schizophrenia had a mild impairment in dual processing. Twenty-one percent showed normal performance on all tests. Fewer subjects with schizophrenia were impulsive/hyperactive, and fewer were impaired in sustained attention compared with the ADHD-C and ADHD-I groups, respectively.
Conclusion: Attention tests are not sufficiently sensitive to attention deficits in everyday functioning. Taking this into account, the possibility still remains that a substantial portion of subjects with schizophrenia are not impaired in attention.