Background. The evolutionary consequences of love are so important that there must be some long-established biological process regulating it. Recent findings suggest that the serotonin (5-HT)
transporter might be linked to both neuroticism and sexual behaviour as well as to
obsessive–compulsive disorder (OCD). The similarities between an overvalued idea, such as that
typical of subjects in the early phase of a love relationship, and obsession, prompted us to explore
the possibility that the two conditions might share alterations at the level of the 5-HT transporter.
Methods. Twenty subjects who had recently (within the previous 6 months) fallen in love, 20
unmedicated OCD patients and 20 normal controls, were included in the study. The 5-HT
transporter was evaluated with the specific binding of 3H-paroxetine
(3H-Par) to platelet membranes.
Results. The results showed that the density of
3H-Par binding sites was significantly lower in
subjects who had recently fallen in love and in OCD patients than in controls.
Discussion. The main finding of the present study is that subjects who were in the early romantic
phase of a love relationship were not different from OCD patients in terms of the density of the
platelet 5-HT transporter, which proved to be significantly lower than in the normal controls. This
would suggest common neurochemical changes involving the 5-HT system, linked to psychological
dimensions shared by the two conditions, perhaps at an ideational level.