BackgroundMajor Depressive Disorder (MDD) is the leading cause of disability worldwide. The cardinal features of MDD are depressed mood and anhedonia. Anhedonia is defined as a “markedly diminished interest or pleasure in all, or almost all, activities of the day”, and has generally been investigated on group-level using retrospective data (e.g. via questionnaire/interview). However, inferences based on group-level findings not necessarily generalize to daily life experiences within individuals.MethodsWe repeatedly sampled pleasurable experiences within individuals’ daily lives by means of Experience Sampling Methods, and compared how positive affect unfolded in the daily life of healthy controls versus patients diagnosed with MDD and anhedonia. We sampled Positive Affect (PA) and reward experiences on 10 semi-random time points a day, for seven days in the daily lives of 47 MDD patients with anhedonia, and 40 controls.ResultsMultilevel models showed that anhedonia was associated with low PA, but not to differences in PA dynamics, nor reward frequency in daily life. In reaction to rewards, MDD patients with anhedonia showed no difference in their increase in PA (i.e., PA reactivity), and showed no signs of a faster return to baseline thereafter (i.e., PA recovery).ConclusionsOur results suggest that the dynamical signature of anhedonia in MDD can be described best as a lower average level of PA, and “normal” in terms of PA dynamics, daily reward reactivity and reward recovery. Preregistration: https://osf.io/gmfsc/register/565fb3678c5e4a66b5582f67. Preprint: https://osf.io/cfktsElectronic supplementary materialThe online version of this article (10.1186/s12888-018-1983-5) contains supplementary material, which is available to authorized users.

Anhedonia is a major public health concern and has proven particularly difficult to counteract. It has been hypothesized that anhedonia can be deterred by engagement in rewarding social and physical events. The aims of the present study were to examine (1) the effects of personalized lifestyle advice based on observed individual patterns of lifestyle factors and experienced pleasure in anhedonic young adults; and (2) whether a tandem skydive can enhance the motivation to carry out the recommended lifestyle changes. Participants (N = 69; M = 21.5, SD = 2.0; 79.7% female) were selected through an online screening survey among young adults. Inclusion criteria were persistent anhedonia and willingness to perform a tandem skydive. Participants filled out questionnaires on their smartphones for 2 consecutive months (3 times per day). After the first month, they were randomly assigned to one of three groups: (1) no intervention, (2) lifestyle advice, and (3) lifestyle advice and tandem skydive. The momentary questionnaire data were analyzed using interrupted time series analyses (ITSA) in a multilevel model and monthly pleasure and depression questionnaires by repeated measures ANOVA. No group differences were found in monthly depression and pleasure scores, but the momentary data showed higher positive affect (PA) and pleasure ratings in the month following the intervention in the two intervention groups than in the control group. The tandem skydive did not have any effects above the effects of the lifestyle advice. Our results indicate that providing personalized lifestyle advice to anhedonic young adults can be an effective way to increase PA and pleasure.

Individuals with anhedonia are likely less 'flat' or 'blunted' than generally thought. Although replication is warranted, impairments in high-arousal positive emotions may be of particular interest in the clinical treatment of anhedonia.