Depression With Anhedonia vs Dysthymia: Do We Understand the Difference?

CLINICIAN’S CORNER

What Is Anhedonia?

Anhedonia is a term used to describe the inability to experience pleasure from activities that are usually found enjoyable, such as eating, exercising, social interactions, or hobbies. It is a core symptom of various mental health disorders, including depression, schizophrenia, and other mood disorders. Individuals with anhedonia may find it difficult to feel joy or satisfaction, which can significantly impact their quality of life and daily functioning. The DSM-5 diagnosis of depression requires the presence of at least 5 symptoms over a period of 2 weeks. At least 1 of these 5 symptoms must be either: (1) depressed mood or (2) a loss of interest and pleasure.¹ While anhedonia is not explicitly named, it is captured as a core symptom of depression. Anhedonia is readily recognized by clinicians and its relevance has been reinforced by psychological theories of positive and negative effect,² evolving neuroscience,³ and clinical outcomes.⁴

While the majority of anhedonia research involves depression, this multi-dimensional symptom plays an important role in many disorders including schizophrenia, addiction, and even neurologic disorders such as Parkinson disease.^5,6 Anhedonia can be further delineated into anticipatory anhedonia, a reduced capacity to anticipate pleasurable activity, and consummatory anhedonia, a reduced experience of pleasure within activity participation.⁷ Individuals with anticipatory anhedonia may struggle to plan and initiate activities due to reduced motivation and interest (Table 1). Consummatory anhedonia may present as the absence of enjoyment or reward during pleasurable activities such as sex, eating, or engagement in activities previously enjoyed. Neuropsychological research suggests dysfunction of dopamine signaling in the ventral striatum (anticipatory) and the prefrontal cortex (consummatory).^7-9

The assessment of anhedonia is difficult as it is a subjective experience. Additionally, anhedonia is not a stable trait and severity may fluctuate, often worsening in an acute depressive episode. The presence of a long-term impairment of pleasure with a temporal component may be suggestive of dysthymia or substance use disorders.⁷ A common clinical assessment tool is the Snaith-Hamilton Pleasure Scale, a 14-item self-report questionnaire designed for use within major depressive disorder (MDD).¹⁰

What Is Dysthymia?

Initially, dysthymia was categorized as a personality disorder.¹¹ This early classification may be where the conflation with anhedonia began. Today, however, dysthymia is known as persistent depressive disorder (PDD). In 2013, the American Psychiatric Association (APA) combined the former diagnoses of dysthymia and chronic MDD into the new diagnosis of PDD to capture the chronicity of the depressive symptoms and the full scope of the disorder’s severity.¹ There are some clinicians who disagree with this diagnostic change, believing that dysthymia captured a chronic and more mild presentation of depression and should continue to be a stand-alone diagnosis. The APA further solidified PDD as the only diagnosis for chronic depression by removing the parenthetical “dysthymia” in the updated DSM-5-TR.^1,12 To add further confusion, the APA included a PDD specifier of “pure dysthymic syndrome” which specifies the temporal component, meeting diagnostic chronicity (at least 2 years), without meeting the full diagnostic criteria for a major depressive episode.¹² Table 2 shows a comparison of depression, anhedonia, and PDD.

The DSM-5 diagnosis of PPD requires the presence of a depressed mood for most of the day, for more days than not, over a period of at least 2 years, and there cannot be an absence of symptoms for more than 2 months at time. While the patient feels depressed there must also be at least 2 or more of the following: (1) poor appetite or overeating, (2) insomnia or hypersomnia, (3) low energy or fatigue, (4) low self-esteem, (5) poor concentration or difficulty making decisions, and (6) feelings of hopelessness.¹ PDD may present with or without a dimension of anhedonia. There is not a common clinical assessment tool specifically for the newer diagnosis of PDD; however, the Cornell Dysthymia Rating Scale (CDRS) is a 20-item self or clinician rated scale that has been psychometrically tested and found to be valid in establishing the frequency and severity of dysthymia symptoms with higher scores indicating a greater severity of symptoms.¹³

The neurobiological research findings are similar to MDD with dysregulation of monoamines and sleep structure,^14-15 decrease in brain derived neurotrophic factor, increase in inflammatory markers, and changes in brain volume as well as changes in the limbic system and prefrontal cortex.^16-17 The temporal component most strongly differentiates PDD from MDD, but clinical similarities can make differentiating between PDD and MDD difficult. Differentials such as substance use and personality disorders must be ruled out; in addition, the clinician must recognize that substance use and personality disorders are often comorbid with PDD.^1,12,15

Why Is This Important?

Diagnostic clarity between anhedonia and PDD (formerly dysthymia and chronic MDD) is paramount in clinical practice to ensure effective and safe treatment for patients. While psychiatry is progressively embracing a dimensional approach to understanding mental health disorders, categorical diagnoses remain essential as they encapsulate specific symptom clusters that guide evidence-based therapeutic interventions. Anhedonia (a multi-dimensional core symptom), characterized by a loss of interest or pleasure in most activities (Table 2), and PDD (a specific syndrome or cluster of symptoms) a persistent low mood, though related, necessitate distinct treatment strategies. Utilizing the wrong diagnostic category can be likened to fitting a car with inappropriate tires; while the vehicle might still function, it is unlikely to perform optimally and may even incur damage over time. Just as the right tires are crucial for a car's performance and safety, accurate psychiatric diagnoses are vital for tailoring effective treatment plans that optimize patient outcomes and prevent potential harm.

Dedicated to early career clinicians, Clinician’s Corner aims to provide helpful information in an approachable and supportive manner. If you have topics that you would like Drs Asbach and Roque to discuss, please submit suggestions to PTEditor@mmhgroup.com.

Ms Roque is a clinical associate professor in the Hahn School of Nursing and Health Science at the University of San Diego. Mr Asbach is a psychiatric physician associate and serves as associate director of interventional psychiatry at DENT Neurologic Institute in New York.

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