The serum prolactin (PRL) levels were measured in 11 depressed patients

as compared with those of 20 normal subjects and 20 schizophrenics. The results showed that the serum prolactin levels of schizophrenics and depressives were higher than those of normal subjects

but the difference of the results between normal subjects and schizophrenics

or schizophrenics and depressives was not signifleant(P>0.05). However there was a significant difference between depressives in attack and normal subjects (P<0.05).The authers consider that the increased levels of serum PRL in depressed patients are probably due to relevant decrease of DA. Therefore

it is suggested that besides the 5-HT and NE Theories

the disturbunce of DA system may be related to the etiology and pathogenesis of depression. Further investigations are needed.