Plasma dopamine beta hydroxylase activity in affective disorders.

Plasma dopamine beta hydroxylase (DBH) activity was measured in patients with affective disorders and in their relatives. The groups studied had wide distributions of values for plasma DBH activity. No significant difference of plasma DBH activity was found between unipolar and bipolar patients, nor between patients given lithium or placebo. Exercise on a treadmill at 40 degrees or 10 degrees C elicited a different pattern of response for plasma DBH activity in three patients as compared to control subjects. In familial studies we found the values of plasma DBH activity to be almost identical in monozygotic twin pairs and quite similar in dizygotic twin pairs. All pairs, however, were discordant for affective illness. There was also a marked similarity of plasma DBH activity in 15 pairs of the same sex sibs discordant for affective illness. These studies suggest that the resting level of plasma DBH activity is not related to affective illness but is genetically determined.