Personality factors predisposing to depression correlate significantly negatively with M1-muscarinic and beta-adrenergic receptor densities on blood cells.

A relationship between psychological and neurobiological predisposition factors for affective disorders has been suggested. The aim of the present study was to test this hypothesis. As predisposition measures of affective disorders, muscarinic and beta-adrenergic receptors densities on blood cells and personality traits were determined in 16 male volunteers. The Minnesota Multiphasic Personality Inventory (MMPI), Freiburger Personality Inventory (FPI), and Premorbid Personality Inventory (PPI) were used for personality assessment. The erythrocyte muscarinic receptor density (mainly M1 subtype) correlated highly significantly negatively with depression on the MMPI (r = -0.71; P less than 0.001) as well as significantly positively with reactive aggressiveness (dominance) on the FPI (r = 0.48; P less than 0.05) and extraversion on the PPI (r = 0.46; P less than 0.05). The beta-adrenoceptor density on lymphocytes correlated significantly negatively with spontaneous aggressiveness (r = -0.51; P less than 0.05) on the FPI. These results are the first evidence that premorbid personality traits of depressives are related to M1-muscarinic and beta-adrenergic receptors densities. It is speculated that decreased beta-adrenergic receptor densities might predispose an individual to major depression whereas a decrease of M1-muscarinic receptor densities could play a role in the development of minor depressions. The findings of the present study are compatible with the postulated relationship between personality and neurobiological predisposition factors of depressive disorders. They suggest the participation of neurobiological factors in the development of personality traits predisposing to depression. However, they seem to be nonspecific for depression and are probably neither a sufficient nor a necessary cause of this disorder. Additional biological or psychological factors seem to be required for the development of clinical depressions.