What are the causes of loss of interest (anhedonia) in adults?

Causes of Loss of Interest (Anhedonia) in Adults

Loss of interest in activities (anhedonia) is primarily a cardinal symptom of major depressive disorder, but also occurs in anxiety disorders, schizophrenia, substance use disorders, and as a side effect of certain medications. 1, 2

Primary Psychiatric Causes

Major Depressive Disorder

• Anhedonia is one of the two essential diagnostic criteria for major depression, alongside depressed mood—at least one must be present for diagnosis. 1, 2, 3
• The American Psychiatric Association requires at least 5 total symptoms present for 2 weeks, with anhedonia or depressed mood being mandatory. 2, 3
• Anhedonia represents a deficit in the brain's reward system, specifically affecting reward anticipation, consumption, and learning mechanisms involving the ventral striatum and prefrontal cortex. 4, 5
• Depression causes inability to sustain positive affect over time, with reduced nucleus accumbens activity during positive experiences. 6

Anxiety Disorders

• Generalized anxiety disorder and other anxiety conditions frequently present with loss of interest or pleasure in activities. 1, 5
• The overlap between anxiety and anhedonia reflects shared deficits in positive valence systems. 5, 7

Schizophrenia and Psychotic Disorders

• Anhedonia is a hallmark symptom of schizophrenia, reflecting deficits in hedonic capacity and reward processing. 4, 5

Substance Use Disorders

• Active substance abuse and withdrawal states commonly cause anhedonia through disruption of dopaminergic reward pathways. 5

Medical and Neurological Causes

Cancer and Chronic Medical Illness

• Adults with cancer frequently develop depressive symptoms including anhedonia, particularly during active treatment, at diagnosis of recurrence, or when approaching end of life. 1
• Chronic medical diseases increase risk for depression and associated anhedonia. 1

Atopic Dermatitis

• Adults with atopic dermatitis have moderate certainty evidence of association with clinician-diagnosed depression, which includes anhedonia as a core feature. 1

Neurological Conditions

• Post-stroke patients may develop anhedonia as part of post-stroke depression. 3
• Cognitive decline and neurodegenerative conditions are associated with depressive symptoms including loss of interest. 1

Medication-Induced Causes

SSRI Antidepressants (Paradoxical Effect)

• Sertraline and other SSRIs can initially cause or worsen anxiety and agitation, which may manifest as decreased interest in activities during the first weeks of treatment. 8
• This typically resolves within 2-4 weeks with proper dose management. 8

Demographic and Social Risk Factors

High-Risk Populations

• Women are at increased risk compared to men for developing depression with anhedonia. 1
• Unemployed individuals and those of lower socioeconomic status have elevated risk. 1
• Older adults facing medical illness, cognitive decline, bereavement, or institutional placement. 1
• Individuals with family history of depression. 1

Life Circumstances

• Personal transitions, family crises, or significant life stressors can trigger depressive episodes with anhedonia. 1

Critical Clinical Considerations

Suicide Risk Assessment is Mandatory

• Anhedonia combined with other depressive symptoms significantly increases suicide risk and requires immediate evaluation. 1, 2
• The American Academy of Pediatrics emphasizes that loss of interest in previously enjoyed activities is a major warning sign for depression and suicidal ideation in adolescents and young adults. 1, 2
• Direct questioning about current suicidal thoughts, specific plans, access to lethal means (especially firearms), and previous attempts is necessary. 1, 2
• Safety takes precedence over confidentiality when suicide risk is present. 1

Screening Approach

• Use the 2-item PHQ-9 screening questions: "Over the past 2 weeks, have you felt little interest or pleasure in doing things?" and "Over the past 2 weeks, have you felt down, depressed, or hopeless?" 1
• If either question scores ≥2 (present more than half the days), proceed to full PHQ-9 assessment. 1
• A PHQ-9 score ≥8 indicates moderate depressive symptoms requiring consultation with psychology or psychiatry. 1

Common Pitfalls to Avoid

• Do not dismiss anhedonia as "normal" stress or aging—it is a pathological symptom requiring evaluation. 1, 2
• Do not confuse neurovegetative symptoms (sleep, appetite, energy changes) with anhedonia itself, though they commonly co-occur. 3
• In medically ill patients, do not attribute anhedonia solely to physical illness without screening for depression. 1, 3
• In adolescents and young adults, recognize that depression may present as irritability rather than classic sadness, but anhedonia remains a key diagnostic feature. 1, 2

Special Populations Requiring Tailored Assessment

• Use culturally sensitive assessments when possible. 1
• Tailor assessment for those with learning disabilities or cognitive impairments. 1
• Be aware of difficulty detecting depression in older adults, where anhedonia may be subtle. 1