New Therapeutic Treatments for Anhedonia

Writer: Sebastian Escobar

Editor: Maylyn Mei and Keila Cruz

Anhedonia is characterized as the loss of interest in daily activities or activities previously found to be pleasurable. An example of anhedonia would be someone who enjoys going to the gym. One day, this individual feels less enjoyment and less motivated to go to the gym. This results in the person going to the gym less and further diminishing their joy or motivation for the gym. Neurological research has indicated that anhedonia is caused by low activity in the ventral striatum, which leads to deficits in the anticipation of rewards (Craske et al., 2023). Experiencing anhedonia places individuals at risk for suicidal ideation, treatment nonresponse, and symptom relapse (Craske et al., 2016). Those with anhedonia are at risk for exacerbation of existing comorbid conditions as well as possible development of new disorders. Positive Affect Treatment (PAT) takes a neuroscience-driven approach to directly address the underlying deficits in the appetitive motivational system that characterizes anhedonia. We aim to examine PAT through the lens of the tripartite model of fear, anxiety, and depression. We argue that PAT offers superior outcomes compared to traditional cognitive-behavioral treatments. This analysis will shed light on the potential benefits found in the integration of  PAT into clinical practice, particularly in enhancing treatment efficacy for unipolar depression and anxiety disorders.

Literature examining the models of anxiety and depression has consistently identified at least two primary systems responsible for regulating thoughts, behaviors, and emotions. More recent models have greater complexity and hierarchical structures, but continue to identify these two systems. The first is the approach or appetitive system (positive affect), which drives goal-directed behavior and is associated with positive emotions like enthusiasm and pride. The second is the withdrawal or defensive system (negative affect), which promotes behavioral inhibition to avoid negative outcomes or punishment. Negative affect is commonly associated with negative emotions like fear and sadness (Craske et al., 2016). Anxiety and depression have been found to occur when there is an excess of negative affect and a deficiency of positive affect. 

Anhedonia has been linked to a deficit in positive affect, it is also connected to several psychiatric conditions. For instance, anhedonia is associated with the major symptoms of depression, with one in three individuals experiencing depression having clinically significant anhedonia (Craske et al., 2016). A previous study has also suggested that anhedonia is present in 75 percent of individuals with depression when not accounting for clinical and non-clinical populations (Franken et al., 2007). Non-clinical participants with depression did have symptoms related to anhedonia but did not meet enough criteria to meet the clinical diagnosis (Franken et al., 2007). Low levels of positive affect are associated with the symptoms of social anxiety disorder, generalized anxiety disorder, and posttraumatic stress disorder. Furthermore, anhedonia has also been linked to schizophrenia and substance use disorder. Due to anhedonia representing a substantial amount of psychopathology that crosses diagnostic boundaries, it can be described as being transdiagnostic (Craske et al., 2016).

Drawing from affective neuroscience research, reward processing can be divided into three components: reward anticipation, reward consumption, and reward learning. Reward anticipation is the ability to anticipate, want, or be motivated to receive future rewards (Craske et al., 2016). Reward consumption is the pleasurable experience of consuming the reward. Reward learning is the process of learning what leads to rewards and adapting behavior accordingly. A person’s reward processing can be affected by the presence of anhedonia. Anhedonia is associated with reduced activation in the ventral striatum, which is implicated in the anticipation of reward. This leads to anhedonic individuals showing reduced behavioral effort to obtain rewards. Anhedonia has been linked to low heart rate acceleration when anticipating rewards. Anhedonia is also associated with hypoactivity in the ventral striatum and orbitofrontal cortex when experiencing pleasurable stimuli, which relates to reduced facial expressions, startle blink reflex modulation, and cardiac acceleration in response to positive stimuli. This lack of response to positive stimuli suggests deficits in reward consumption. Finally, anhedonia is linked to reduced activation in reward-related brain regions, like the prefrontal cortex, during reward learning tasks (Craske et al., 2016; Craske et al., 2019).

According to past studies, self-reported anhedonia is a strong predictor of suicidal thoughts and behaviors in individuals with major depression, even when accounting for other depressive symptoms (Fawcett et al., 1990; Winer et al., 2014). The presence of anhedonic symptoms has also been shown to predict a poorer response to both medication and psychological treatments for depression and related disorders. Current pharmacological treatments have been found to have an inadequate response when treating depressed individuals with anhedonia and may worsen anhedonic symptoms  (Craske et al., 2016). For psychological treatments, behavioral activation (BA) therapy has been implemented to increase responses to positive reinforcements. BA therapy utilizes behavioral models that assume that depressed individuals obtain less positive reinforcement than other individuals because they engage less frequently in pleasant activities and enjoy activities less. BA in action can look like monitoring a person’s mood and activities, patients learning to understand the connection between what they do and how they feel, and using this knowledge to schedule activities that create an atmosphere of positive reinforcement and solve problems that prevent them from doing so (Janssen et al., 2020). However, studies have yet to explain the effects of behavioral therapy on positive affects and have shown only limited effects on levels of positive affect or anhedonia. Clinical trials measuring the effects of cognitive therapy and antidepressant medication showed they could reduce negative affect to standard levels but had little effect in increasing positive affect (Craske et al., 2016). Current treatment strategies tend to be focused on negative affects such as Cognitive behavioral therapy (CBT), which aims to change negative behaviors by challenging skewed cognitions rather than focusing on the positive aspects. Treatment strategies that can target the underlying mechanisms of anhedonia are needed to improve treatment effects. 

Michelle Craske (2016) developed PAT, an intervention designed to target deficits in reward sensitivity comprising three modules. Each module targets different aspects of reward processing. The first module combines planning for pleasurable activities and reinforcement of the mood effects of said activities. It includes "in-the-moment" recounting exercises designed to develop an appreciation for these pleasurable activities. This is done by promoting that clients engage in daily activities that are considered pleasurable and give a sense of accomplishment. During sessions, therapists guide clients to imagine and recall their pleasurable activities in the present tense. While recalling activities, therapists are guided to make note of the physical sensations, thoughts, behaviors, and positive moods. The goal of this module is to utilize behavioral activation training to motivate rewarding activities, reward learning, and reward consumption. The second module contains exercises for identifying positive aspects of experience, identifying aspects of one's behavior that contributed to positive outcomes, and practicing present-tense imagining of details of future positive events. This module utilizes several techniques. The first technique, named Silver Lining, trains clients to recognize positive aspects of everyday events, even events that are considered negative. The second technique, called Taking Ownership, is where clients practice identifying behaviors that result in positive outcomes in their daily lives and savor the positive emotions from the outcome. Clients are instructed to recite their accomplishments out loud in front of a mirror to deepen their experience of receiving rewards. The third technique, called Imagining the Positive, is where clients imagine as many positive aspects as possible of an upcoming event. The goal of this module is to utilize cognitive training to alter perceptions of reward behaviors (Craske et al., 2016; Craske et al., 2019). The third and final module contains kindness, generosity, gratitude, and appreciative joy exercises designed to appreciate and enjoy positive experiences. These include daily practices of mentally sending positivity to others who are suffering and engaging in acts of generosity without expecting something in return, wishing for happiness and fortune to oneself and others, and promoting feelings of gratefulness. The goal of this module is to foster a positive perception of oneself and others while encouraging engagement in rewarding experiences.  (Craske et al., 2016; Craske et al., 2023). 

Two clinical trials led by Craske et al. (2019, 2023) found that PAT resulted in greater improvements in positive affect compared to the Negative Affect Treatment (NAT), as measured by the Positive and Negative Affect Schedule. Negative affect treatment was a treatment developed for the study that only focused on targeting negative affect. Negative affect was already reported to decrease more significantly in participants who underwent PAT when compared to NAT. Participants in PAT also reported lower symptoms of depression, anxiety, and stress at the six-month follow-up, with a medium-to-large effect size. The probability of reporting suicidal ideation at the six-month follow-up was lower in PAT compared to NAT.

Some of the limitations of these two trials include the lack of generalizability from an academic background to a community setting. The starting criteria for low positive affect made most participants ineligible for the trials, which also reduces generalizability. These studies also heavily relied on self-reported measures as well as estimates of treatment response. Finally, NAT does not fully represent CBT for depression and points to future research using a third control treatment (Craske et al., 2023). 

Consequently, the Positive Affect Treatment (PAT), developed by Dr. Craske, has shown greater effectiveness in increasing positive affect while reducing negative affect, anxiety, and symptoms of unipolar depression. Future research should focus on comparing PAT to standard Cognitive Behavioral Therapy (CBT), refining reward learning measures, and exploring additional aspects of reward sensitivity. Moving forward, prioritizing treatment strategies that directly address the positive affect of anhedonia has the potential to significantly improve patient outcomes.