Altered interaction with environmental reinforcers in major depressive disorder: Relationship to anhedonia

Abstract

Anhedonia-defined as loss of interest or pleasure-is one of two core symptoms of major depressive disorder (MDD). Anhedonia may involve decreased enjoyment of potentially rewarding activities and decreased motivation to engage in such activities. Increased engagement with reinforcers-activities with the potential to be positive experiences-is a frequent target of cognitive-behavioral therapies. Nevertheless, how environmental reinforcers are perceived, and how decisions to approach or avoid them are made by individuals with MDD, is largely unknown. We developed an experimental Behavioral Approach Motivation Paradigm to study how activities are evaluated and approached in MDD. Twenty-one MDD participants and 23 healthy controls performed an experimental task that rated activity words for their hedonic value, then engaged in an approach-avoidance joystick task with each individual's unique set of 'liked' and 'disliked' activity words. A negative correlation was observed between anhedonia and the number of 'liked' activities across participants. No significant difference between approach and avoidance behavior was found in direct comparisons between healthy controls and MDD participants; however, weaker avoidance and greater approach toward 'disliked' activities was found in MDD participants. This suggests negative bias in selecting environmental opportunities, potentially further compromising access to hedonic experiences in MDD.

Keywords: Anhedonia; Approach; Avoidance; Behavioral activation; Major depressive disorder; Reinforcement.

Fig. 1

An illustration of the Behavioral Approach Motivation Paradigm (BAMP). In the Word Rating Task (WRT), participants rated how much they ‘liked’ 150 words on a scale from 0 to 4, with 0 and 1 representing ‘disliked’, 2 being ‘neutral’, and 3 or 4 representing ‘liked’. They were allowed to skip up to 10 words and the cursor reset after each item. Next, 15 words were randomly selected and subsequently used in the Lexical Decision Reaction Time Task (LDT), where participants were required to decide whether an item was a word or a non-word (scrambled target words), and push or pull the joystick depending on the item category.

Fig. 2

Results of the activity Word Rating Task (WRT), mean, SD. Healthy controls rated more words as ‘liked’ and fewer as ‘disliked’ than participants with major depressive disorder (MDD). Both groups rated more words as ‘liked’ than ‘disliked’.

Fig. 3

Approach and avoidance of ‘liked’ and ‘disliked’ stimulus words, mean, SEM. Response duration: group × direction × valence, p < 0.01. MDD: major depressive disorder; HC: healthy control.