It seems that it's impossible to distinguish an obsessional neurosis from an intense love from a biochemical perspective. - Il semble impossible de distinguer une névrose obsessionnelle d'un amour intense, d'un point de vue biochimique.
{n} neurosis, any of several mental disorders involving physical and emotional symptoms (such as bodily pain, anxiety, depression, etc.) that do not stem from any obvious physiological change (Medicine)