In psychoanalysis, cathexis (or emotional investment) is defined as the process of allocation of mental or emotional energy to a person, object, or idea.
The Greek term cathexis (κάθεξις) was chosen by James Strachey to render the German term Besetzung in his translation of Sigmund Freud's complete works. Freud himself used the word "interest" in English in an early letter to Ernest Jones.
Peter Gay objected that Strachey's use of cathexis was an unnecessarily esoteric replacement for Freud's use of Besetzung – "a word from common German speech rich in suggestive meanings, among them 'occupation' (by troops) and 'charge' (of electricity)", though Gay is mistaken regarding his latter example. Gay may have been confused by the common use of the English word "charge" to refer to both "allocation/allocating" and the "energy" allocated in cathexis, e.g. "emotional charge", "counter-charge", "to charge with an affect".
Freud defined cathexis as an allocation of libido, pointing out for example how dream thoughts were charged with different amounts of affect. A cathexis or allocation of emotional charge might be positive or negative, leading some of his followers to speak of a cathexis of mortido as well. Freud called a group of cathected ideas a complex.
Freud frequently described the functioning of psychosexual energies in quasi-physical terms, representing frustration of libidinal desires, for example, as a blockage of (cathected) energies which would eventually build up and require release in alternative ways. This release could occur, for example, by way of regression and the "re-cathecting" of former positions or fixations, or the autoerotic enjoyment (in phantasy) of former sexual objects: "object-cathexes".
Freud used the term "anti-cathexis" or counter-charge to describe how the ego blocks such regressive efforts to discharge one's cathexis: that is, when the ego wishes to repress such desires. Like a steam engine, the libido's cathexis then builds up until it finds alternative outlets, which can lead to sublimation, reaction formation, or the construction of (sometimes disabling) symptoms.