Depression is a complex mood disorder that can severely impact daily life. Major Depressive Disorder (MDD) and Persistent Depressive Disorder (PDD) are two primary forms, each with distinct diagnostic criteria and characteristics that affect how people think, feel, and function.

Understanding these disorders is crucial for recognizing symptoms and seeking help. From duration and severity to subtypes and specifiers, depression manifests differently in individuals, influencing social relationships, work performance, and overall well-being. Recognizing these impacts can lead to better support and treatment options.

Major Depressive Disorder (MDD) and Persistent Depressive Disorder (PDD)

Diagnostic criteria of MDD and PDD

• Major Depressive Disorder (MDD)
  • Depressed mood and/or loss of interest or pleasure in activities persists for at least 2 weeks
  • At least 5 of the following symptoms must be present during the same 2-week period:
    • Depressed mood experienced most of the day, nearly every day, often described as feeling sad, empty, or hopeless
    • Markedly diminished interest or pleasure in all or almost all activities, most of the day, nearly every day (anhedonia)
    • Significant unintentional weight loss or gain (change of more than 5% of body weight in a month), or decrease or increase in appetite nearly every day
    • Insomnia (difficulty falling or staying asleep) or hypersomnia (sleeping excessively) nearly every day
    • Psychomotor agitation (restlessness, pacing) or retardation (slowed movements, speech) observable by others
    • Fatigue or loss of energy nearly every day, feeling tired and lacking motivation
    • Feelings of worthlessness or excessive or inappropriate guilt (may be delusional) nearly every day
    • Diminished ability to think, concentrate, or make decisions, nearly every day (indecisiveness, difficulty focusing)
    • Recurrent thoughts of death (not just fear of dying), recurrent suicidal ideation without a specific plan, or a suicide attempt or specific plan for committing suicide
  • Symptoms cause clinically significant distress or impairment in social, occupational, or other important areas of functioning
  • Symptoms are not attributable to the physiological effects of a substance (drug abuse, medication) or another medical condition (hypothyroidism)
• Persistent Depressive Disorder (PDD)
  • Depressed mood for most of the day, more days than not, as indicated by subjective account or observation by others, for at least 2 years
  • Presence of at least 2 of the following symptoms while depressed:
    • Poor appetite or overeating, leading to significant weight changes
    • Insomnia or hypersomnia, difficulty regulating sleep patterns
    • Low energy or fatigue, feeling tired and lacking motivation
    • Low self-esteem, feelings of inadequacy or self-criticism
    • Poor concentration or difficulty making decisions, problems with focus and indecisiveness
    • Feelings of hopelessness, pessimism about the future
  • During the 2-year period, the individual has never been without the symptoms for more than 2 months at a time
  • Symptoms cause clinically significant distress or impairment in social, occupational, or other important areas of functioning

MDD vs PDD characteristics

• Duration
  • MDD: Depressive episode lasts at least 2 weeks but typically remits within months
  • PDD: Depressed mood persists for at least 2 years, with symptoms being chronic and long-lasting
• Severity
  • MDD: Typically more severe, with a greater number and intensity of symptoms that significantly impact functioning
  • PDD: Generally less severe than MDD, but persistent and chronic, with symptoms that may fluctuate in intensity over time
• Symptom presentation
  • MDD: Requires at least 5 symptoms, including depressed mood and/or loss of interest or pleasure (anhedonia), along with other physical, cognitive, and emotional symptoms
  • PDD: Requires depressed mood plus at least 2 additional symptoms, which may be less severe than in MDD, but are persistent and long-lasting

Subtypes and specifiers in depression

• MDD subtypes and specifiers
  • Melancholic features: Severe symptoms, including profound anhedonia, excessive guilt, psychomotor changes (retardation or agitation), and distinct quality of depressed mood (despair, emptiness)
  • Atypical features: Mood reactivity (ability to experience improved mood in response to positive events), increased appetite or significant weight gain, hypersomnia, leaden paralysis (heavy, leaden feelings in arms or legs), and interpersonal rejection sensitivity
  • Psychotic features: Presence of delusions (fixed, false beliefs) and/or hallucinations (sensory experiences in the absence of external stimuli) during the depressive episode
  • Peripartum onset: Onset of symptoms during pregnancy or within 4 weeks postpartum, often associated with significant anxiety and concerns about the baby
  • Seasonal pattern: Regular onset and remission of depressive episodes based on seasons (usually winter), known as Seasonal Affective Disorder (SAD)
• PDD specifiers
  • With pure dysthymic syndrome: No major depressive episodes during the first 2 years of the disorder
  • With persistent major depressive episode: Meets criteria for both PDD and MDD throughout the 2-year period, with no remission of symptoms
  • With intermittent major depressive episodes, with current episode: Meets criteria for PDD, with a current MDD episode superimposed on the persistent depressive symptoms
  • With intermittent major depressive episodes, without current episode: Meets criteria for PDD, with a history of MDD episodes but not currently experiencing one

Impact of depression on functioning

• Impairment in social, occupational, and educational functioning
  • Reduced productivity and performance at work or school due to lack of motivation, concentration difficulties, and absenteeism
  • Strained interpersonal relationships and social withdrawal, leading to isolation and loneliness
• Increased risk of physical health problems
  • Cardiovascular disease (heart attack, stroke), diabetes, and other chronic conditions due to neglect of self-care and unhealthy lifestyle choices
  • Weakened immune system and increased susceptibility to illnesses and infections
• Reduced self-care and neglect of personal hygiene, leading to deterioration in physical appearance and overall health
• Increased risk of substance abuse and addiction as a means of self-medication or coping with depressive symptoms
• Decreased overall life satisfaction and well-being, with a pessimistic outlook on life and a sense of hopelessness
• Increased risk of suicidal thoughts, attempts, and completed suicide due to feelings of despair, worthlessness, and a desire to end the emotional pain