Many authors support the idea that Mood Incongruent Psychosis is a subtype of affective illness, although no clear definition or etiopathogenic basis of the congruent or incongruent subtype has been found.

In this study we intend to evaluate clinical and biological differences between Psychotic Bipolar I patients who have mood congruent or mood incongruent psychotic symptoms.

The study has been carried out in 80 Psychotic Bipolar I Patients before, and after, four weeks of treatment with Olanzapine plus Lithium. We studied the correlation between the plasma concentration, before treatment, of the dopamine metabolite 3,4 Dihydroxyphenylacetic acid (DOPAC) and the clinical response to treatment.

The most remarkable result found was that Clinical Improvement after 28 days of treatment correlated positively with the initial concentration of DOPAC, but ONLY in the subgroup of patients with congruent psychotic symptoms.

From our results it seems that the Congruence and Incongruence of psychosis in bipolar I patients can provide a basis to objectively divide these patients. Both groups can be distinguished based on the relationship established between their concentration of DOPAC before treatment and their clinical response to the pharmacological treatment.

Universidad del País Vasco Grant N° EHU 09/21 and Fondo de Investigación Sanitaria and Feder Founds Grant N° 09/01760.