The anhedonias: a conceptual history.
BACKGROUND: The term and concept of 'anhedonia' refer to a group of clinical phenomena whose common denominator is the complaint of a putative incapacity to 'experience pleasure". Linked to disorders such as schizophrenia and depression, anhedonia remains difficult to define and measure. METHOD: This paper explores the historical frames in which anhedonia was originally constructed; and is fully based on primary sources. It makes use of the 'conceptual method', i.e. it differentiates the history of the word from that of the behaviours and concepts involved. RESULTS: Historical analysis shows that the boundaries of 'anhedonia' have been fuzzy since the time of Ribot, and that this has made it conceptually unstable. One reason for this instability pertains to the fact that from the start its definition has been parasitical upon the (itself evolving) concept of 'pleasure'. Another that it is defined negatively, i.e. as a reduction or abolition in a putative unitary function. Yet another, that there is little evidence that anhedonia itself is a unitary phenomenon. CONCLUSIONS: It is concluded that at this stage it might be advisable to refer to the concept in the plural (the anhedonias); that a definition should be formulated that it is less dependent upon the ongoing concept of pleasure; and that far more empirical research is needed to find out whether anhedonia is more than a final common pathway.