EXPERIMENTAL MEASUREMENT OF BEHAVIORAL APPROACH MOTIVATION IN MAJOR DEPRESSIVE DISORDER
LEJUEZ, CARL W
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Major Depressive Disorder (MDD) presents a significant public health challenge. Given the symptoms heterogeneity and widespread changes in brain structure and Function in MDD, there may be several subtypes of depression not sufficiently distinguished by current diagnostic criteria but important to recognize to improve clinical outcomes. One of the two core symptoms of MDD is `markedly diminished interest or pleasure in all, or almost all, activities most of the day, nearly every day' and is often referred to as anhedonia (DSM-IV, V). Anhedonia may have a variety of underlying causes such as not finding previously enjoyed activities appealing, lacking motivation to engage or reluctance to put forth necessary effort, and these processes may be quite unique and not differentiated by current assessment methods (Treadway & Zald, 2011). It has been long recognized that depression is associated with insufficient environmental reinforcement (Peter M. Lewinsohn & Graf, 1973) and treatments were developed to address this deficiency (Peter M. Lewinsohn, Sullivan, & Grosscup, 1980). Clinical studies of effectiveness of the Behavioral Activation Treatment for Depression (BATD), (Hopko, Lejuez, LePage, Hopko, & McNeil, 2003), suggest that an increase in the engagement in reinforcing activities may be helpful in treatment of depression. However, a crucial aspect of activity related behavior, the initial approach and engagement which necessarily precede potential experience of enjoyment, has not been sufficiently characterized. In the current work, we present the development of an experimental behavioral approach motivation paradigm (BAMP) to study approach motivation to engage in liked activities, and relate experimental results to the symptoms of depression and anhedonia to better characterize approach behavior in MDD. We sought to establish a valid behavioral measure of approach motivation in major depression that will be suitable for behavioral and neuroimaging studies of anhedonia. In the BAMP study, subjects rated activity words for the appetitive value, and later `approached' and `avoided' the stimuli in an implicit joystick task. The findings indicated reduced range of activities rated as liked by depressed patients versus healthy controls, but no difference on an approach measure of liked activities. The depressed group showed a stronger approach rather than avoidance of disliked activities. Thus, `lack of interest or pleasure' may be partially related to excessive approach of mood-maintaining negative experiences, and inadequate avoidance of disliked situations. Further study of altered approach and avoidance behavior could shed additional light on processes underlying anhedonia in Major Depressive Disorder.