Educational Disclaimer: This case study is for educational and informational purposes only. It does not constitute medical advice, clinical guidance, or a substitute for professional psychiatric evaluation. All diagnostic criteria referenced are from the DSM-5-TR (APA, 2022). Clinicians should rely on their professional training, direct patient assessment, and current evidence-based guidelines when making diagnostic and treatment decisions.

Clinical Vignette

Patient: "Ms. S," 37-year-old accountant, self-referred after reading that 'depression doesn't always look like depression' and recognizing herself.

Chief Concern: "I've always been a negative person. I thought that was just my personality. But I'm starting to wonder if I've actually been depressed my entire adult life. I can't remember the last time I felt genuinely happy for more than a day or two."

History of Present Illness: Ms. S describes a pervasive pattern of low mood and pessimism dating to approximately age 18 (19 years). She reports chronically low energy, difficulty making decisions (described as 'analysis paralysis'), low self-esteem ('I'm mediocre at everything'), and a persistent sense of hopelessness about her future. She maintains full-time employment but describes her performance as 'adequate, never impressive.' She has a small social circle but declines most invitations because 'I won't enjoy it anyway.' She sleeps adequately (7-8 hours) but never feels rested. Her appetite is normal. She has never experienced a period exceeding 2-3 weeks without these symptoms since age 18. She has never been hospitalized, never been suicidal, and has never had an episode so severe that she could not function. She has never been treated for depression. She describes periods of 'darker weeks' (occurring 2-3 times per year) during which she adds tearfulness, increased sleep, and greater social withdrawal to her baseline symptoms. These darker periods last 2-3 weeks and then she returns to her usual 'gray' baseline.

Past Psychiatric History: No prior psychiatric treatment. No prior diagnosis.

Family History: Father described as 'chronically pessimistic' (never diagnosed). Aunt: MDD, treated with medication.

Mental Status Exam: Cooperative, but affect is uniformly subdued. Speech normal rate, slightly monotone. Mood 'grayish, like always.' Affect constricted. Thought process linear but pessimistic. No psychotic symptoms. No suicidal ideation. Insight emerging. Judgment intact.

Step 1: Persistent Depressive Disorder DSM-5-TR Criteria

Criterion A: Depressed mood for most of the day, for more days than not, for at least 2 years.

Low mood has been present more days than not for 19 years (since age 18). Far exceeds 2-year minimum. MET.

Criterion B: Two or more of the following while depressed: (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, (6) feelings of hopelessness.

(3) Low energy — present ('never feels rested'). (4) Low self-esteem — present ('mediocre at everything'). (5) Difficulty making decisions — present ('analysis paralysis'). (6) Hopelessness — present (persistent re: future). 4 of 6 criteria met. MET (4/6).

Criterion C: During the 2-year period, the individual has never been without symptoms for more than 2 months at a time.

Has never had a symptom-free period exceeding 2-3 weeks in 19 years. MET.

Criterion D: Criteria for a major depressive episode may be continuously present for 2 years.

Her 'darker weeks' may intermittently meet MDE criteria (tearfulness + increased sleep + social withdrawal added to baseline). DSM-5-TR allows concurrent MDE. NOTED: possible double depression.

Criterion E: No manic or hypomanic episode.

No history of elevated mood, decreased sleep need, or grandiosity. MET.

Criterion F: Not better explained by another disorder.

No psychotic disorder, no schizoaffective disorder. MET.

Criterion G: Not attributable to substance or medical condition.

No substance use. No medical conditions. MET.

Criterion H: Clinically significant distress or impairment.

Social avoidance, self-described underperformance at work, subjective distress about chronic lack of happiness. MET.

Step 2: Specifiers and Double Depression Assessment

DSM-5-TR allows several specifiers for PDD:

Specifier Assessment This Patient
With persistent major depressive episode Full MDE criteria met continuously for 2+ years Baseline does not meet full MDE; only 'darker weeks' approach MDE threshold
With intermittent major depressive episodes, with current episode Current MDE present, with prior 8-week PDD periods Not currently in a 'darker' period; currently at baseline PDD
With intermittent major depressive episodes, without current episode Prior MDEs present but currently only PDD baseline Most applicable: intermittent 'darker weeks' that may meet MDE criteria, currently at PDD baseline
With pure dysthymic syndrome Full MDE criteria have never been met during the 2-year period Difficult to confirm; 'darker weeks' may intermittently meet MDE criteria
Early onset Before age 21 Applies: onset age 18
Late onset Age 21 or after Does not apply

Double Depression

Ms. S likely has 'double depression': chronic PDD baseline ('gray') with intermittent superimposed major depressive episodes ('darker weeks'). This pattern is clinically significant because treatment must address both the chronic baseline and the episodic worsening.

Diagnostic Formulation

Diagnostic Conclusion

Persistent Depressive Disorder, with intermittent major depressive episodes, without current episode, early onset (F34.1): All DSM-5-TR criteria met. Nineteen-year duration (early onset at age 18). Chronic low mood, low self-esteem, hopelessness, low energy, and decision-making difficulty present more days than not. Intermittent worsening ('darker weeks' 2-3x/year, possibly meeting MDE criteria). Treatment: combination of psychotherapy (CBT for chronic depression or CBASP) and pharmacotherapy (SSRI or SNRI as first-line). The chronicity and early onset suggest that extended treatment (years, possibly indefinite) will be needed.

Teaching Points

  • PDD (Dysthymia) is a chronic depressive condition that lasts at least 2 years. Its chronicity often leads patients to experience the symptoms as 'just my personality' rather than a treatable disorder, delaying diagnosis. Ms. S's recognition at age 37 (after 19 years of symptoms) is typical.
  • DSM-5-TR merged the DSM-IV categories of Dysthymic Disorder and Chronic Major Depressive Disorder into PDD. This reflects the clinical reality that chronic low-grade depression and chronic MDD share more similarities than differences in course and treatment response.
  • Double depression (PDD + superimposed MDE) is common. Patients with PDD are at increased risk for developing superimposed major depressive episodes. Treatment of the MDE alone is insufficient; the chronic dysthymic baseline must also be addressed to prevent recurrence.
  • Early-onset PDD (before age 21) is associated with higher rates of comorbid personality disorders, longer illness duration before treatment, and poorer response to short-term psychotherapy. The Cognitive Behavioral Analysis System of Psychotherapy (CBASP) was developed specifically for chronic depression.
  • The distinction between PDD and depressive personality traits is clinically important. PDD is a treatable mood disorder with identifiable onset (even if gradual). Depressive personality traits (if conceptualized) represent stable temperamental features present from childhood. Onset after adolescence and the presence of specific DSM criteria favor PDD over personality.