UNIPOLAR MOOD DISORDERS
Introduction to Unipolar Mood Disorders
Unipolar mood disorders are primarily characterized by periods of depression without episodes of mania or hypomania. The most common forms are:
- Major Depressive Disorder (MDD)
- Persistent Depressive Disorder (Dysthymia)
- Premenstrual Dysphoric Disorder (PMDD)
- Disruptive Mood Dysregulation Disorder (DMDD)
Major Depressive Disorder (MDD)
Definition
Major Depressive Disorder (MDD) is a severe condition characterized by persistent feelings of sadness, worthlessness, and hopelessness, which interfere with daily life.
DSM-5 Diagnostic Criteria for MDD
To be diagnosed with MDD, an individual must exhibit at least 5 symptoms during a 2-week period, including depressed mood or anhedonia:
- Depressed mood most of the day (can be irritable mood in children and adolescents).
- Loss of interest or pleasure in most activities.
- Significant weight loss or gain, or changes in appetite.
- Insomnia or hypersomnia.
- Psychomotor agitation or retardation.
- Fatigue or loss of energy.
- Feelings of worthlessness or excessive guilt.
- Impaired concentration or indecisiveness.
- Recurrent thoughts of death, suicidal ideation, or attempts.
Additional Requirements:
- Symptoms must cause significant distress or impairment in functioning.
- Symptoms must not be attributable to substances, medical conditions, or psychotic disorders.
- History of manic or hypomanic episodes must be ruled out.
Clinical Features of MDD
- Persistent sadness, hopelessness, or emptiness.
- Loss of pleasure in previously enjoyed activities.
- Changes in sleep patterns (insomnia or hypersomnia).
- Changes in appetite (weight gain or loss).
- Psychomotor agitation (fidgeting, restlessness) or retardation (slowed movements).
- Low energy and chronic fatigue.
- Cognitive difficulties, such as impaired concentration and indecisiveness.
- Suicidal ideation or attempts.
Special Symptoms:
- Early morning awakening (waking up at 3-4 AM and unable to return to sleep).
- Delusions and hallucinations: In severe cases, individuals may experience negative delusions or auditory hallucinations.
Prevalence and Onset
- Global prevalence: MDD affects people across all age groups.
- Onset: Commonly emerges around age 30, though it can appear earlier.
- Higher risk during adolescence and in females.
Course and Duration
- Untreated depressive episodes may last 2 weeks to several months.
- Average duration: 2 to 9 months if untreated.
- Chronic episodes can persist for years in severe cases.
Persistent Depressive Disorder (Dysthymia)
Definition
Persistent Depressive Disorder (PDD), also known as dysthymia, is a chronic form of depression lasting at least 2 years in adults (1 year in children).
Key Features
- Low-grade, chronic depressive symptoms.
- Periods of normal mood are brief (lasting a few days to weeks).
Prevalence and Onset
- Lifetime prevalence: 2.5%–6%.
- Onset: Early onset is linked to poor prognosis and familial history of depression.
Course
- Duration: Can last 4–20 years or more.
- Individuals with PDD may experience episodes of Major Depressive Disorder (double depression).
Double Depression
Definition
Double Depression occurs when Major Depressive Episodes develop in individuals with pre-existing Persistent Depressive Disorder.
Course
- Chronic low-grade depression worsens into full episodes of MDD.
- Relapse and recurrence rates are high.
Premenstrual Dysphoric Disorder (PMDD)
Definition
PMDD is a severe form of Premenstrual Syndrome (PMS) that occurs in the luteal phase of the menstrual cycle.
Symptoms
- Emotional symptoms:
- Mood swings, sadness, irritability, and anxiety.
- Physical symptoms:
- Bloating, breast tenderness, headaches, joint pain.
- Symptoms must improve after menstruation begins.
Diagnostic Criteria
- 5 or more symptoms must be present in the final week before menses and improve after onset.
- Symptoms include:
- Marked mood swings, irritability, or anxiety.
- Difficulty concentrating, fatigue, changes in appetite, and physical discomfort.
Disruptive Mood Dysregulation Disorder (DMDD)
Definition
DMDD is characterized by chronic irritability and severe, frequent temper outbursts in children.
Key Features
- Outbursts occur 3 or more times per week.
- Mood between outbursts remains irritable.
- Symptoms persist for at least 12 months in two or more settings (home, school, peers).
- Onset occurs before age 10.
Causal Factors of Unipolar Mood Disorders
Biological Factors
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Genetics:
- Twin studies indicate a heritability rate of 31%–42%.
- Serotonin-transporter gene is implicated.
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Neurochemical Factors:
- Imbalances in neurotransmitters like serotonin, dopamine, and norepinephrine.
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Hormonal Dysregulation:
- Abnormalities in the HPA axis and elevated cortisol levels.
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Brain Structures:
- Prefrontal Cortex: Reduced activity in the dorsolateral and orbital prefrontal cortex.
- Hippocampus: Decreased volume due to prolonged stress.
- Amygdala: Increased activity associated with heightened emotional response.
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Biological Rhythms:
- Sleep disruptions (shorter REM latency, increased REM activity).
- Seasonal Affective Disorder (linked to reduced sunlight exposure).
Psychological Factors
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Cognitive Models:
- Beck’s Cognitive Triad: Negative thoughts about self, world, and future.
- Cognitive Distortions: All-or-nothing thinking, selective abstraction, and arbitrary inference.
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Learned Helplessness Theory:
- Individuals feel powerless to control negative outcomes.
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Hopelessness Theory:
- Pessimistic attributions and feelings of hopelessness increase depression risk.
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Ruminative Response Styles:
- Repetitive negative thinking exacerbates depressive symptoms, particularly in women.
Social Factors
- Stressful Life Events:
- Loss of loved ones, financial difficulties, and chronic illness.
- Lack of Social Support:
- Loneliness and isolation worsen depression.
- Marital Distress:
- High conflict and lack of intimacy increase depressive episodes.
Summary
Unipolar mood disorders, including MDD, PDD, and related subtypes, are caused by a combination of biological, psychological, and social factors. Accurate diagnosis and understanding of causal mechanisms are essential for effective treatment and prevention.
Key Terms
- Anhedonia: Loss of interest or pleasure.
- Double Depression: Co-occurrence of MDD and PDD.
- Cognitive Triad: Negative thoughts about self, world, and future.
- HPA Axis: Hormonal pathway involved in stress regulation.