Background
We previously demonstrated a negative correlation between post-synaptic 5-HT1A receptor density (measured with [11C]WAY-100635 PET) and defensive personality style (assessed as the Eysenck Personality Questionnaire Lie scale, EPQ-L), in 2 independent cohorts of healthy volunteers1, 2. Both 5-HT1A receptor density and defensive personality have been linked to depressive illness. 5-HT1A receptor density decreases in subjects with a history of depression (whether currently depressed or not), raise the possibility of relative 5-HT1A receptor decrease being a pre-disposing factor for the development of depressive illness. The personality trait of defensiveness is linked to an inhibition of the perception of threat and an attenuated experience of negative affect. Subjects with high defensiveness scores have been shown to have a reduced lifetime rate of psychopathology. We therefore explored the relationship between 5-HT1A receptor density, defensiveness and depressive illness.
Methods
5-HT1A receptor density was assessed as previously described1 using [11C]WAY 100635 on the ECAT 953B PET camera, and a basis function implementation of the simplified reference tissue model. Defensiveness was assessed as the score of the EPQ-L questionnaire. A group of 21 antidepressant free, euthymic patients (13 M, 8F), with a past history of major depressive disorder, was examined and the results compared to our database of 65 healthy volunteers (61 M, 4F) assessed previously1, 2. As the EPQ-L correlates significantly with age all comparisons were controlled for age and sex.
Results
We found a highly significant correlation between 5-HT1A receptor density and EPQ-L (r = 0. 626, DF = 17, p = 0.004). In healthy volunteers the equivalent correlation is also highly significant, but negative (r = −0.413, DF = 61, p = 0.001).
Conclusions
We demonstrated that the relationship between 5-HT1A receptor density and the personality trait of defensiveness, is modified by the presence of past depressive illness. Differences in neurochemical-cognitive-behavioural interaction between depressed patients and healthy volunteers, as well as the relationship of these findings to recently demonstrated links between 5-HT1A receptor system and religiosity 3 , will be discussed (See Figure 1).
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