In experimental psychopathology there is a long tradition of reaction time studies. Especially in schizophrenia there has reliably been observed deficits in attention and reaction time.

To examine if patients with schizophrenia can be differentiated from patients with mood disorder on the basis of their reaction time patterns.

To evaluate if reaction time measures might be useful in the diagnostic process.

58 patients with schizophrenia, 55 patients with mood disorder, and 30 healthy controls participated in a computerbased reaction time experiment. The stimuli were short visual and auditory stimuli presented in a randomized sequence. The subjects were instructed to press a button each time they saw or heard a signal from the computer.

The reaction times of the patients with schizophrenia and mood disorder to both light and sound stimuli were significantly slower than those of the control group. Furthermore, the patient groups’ reaction times were significantly less stable than those of the control group, and they made significantly more errrors. However, no significant differences in reaction times, stability of reaction times, and number of errors were found between the two patient groups. No clear or consistent differences were observed when comparing the reaction time patterns of subgroups of schizophrenia patients with positive, mixed and negative symptoms, and mood disorder patients in manic and depressive phases.

On the basis of simple reaction measures it is not possible to differentiate between patients with schizophrenia and mood disorder.