A mental health volunteer is interviewing locals as part of a community outreach program. A 46-year-old man discloses that he has felt sad for as long as he can remember. He feels as though his life is cursed and if something terrible can happen to him, it usually will. He has difficulty making decisions and feels hopeless. He also feels that he has had worsening suicidal ideations, guilt from past problems, decreased energy, and poor concentration over the past 2 weeks. He is otherwise getting enough sleep and able to hold a job. Which of the following statement best describes this patient's condition?

The patient has double depression.

The patient may have symptoms of mania or psychosis.

The patient is likely to show anhedonia.

The patient likely has paranoid personality disorder.

The patient should be started on an SSRI.

A 24-year-old woman presents to her primary care physician for a wellness exam. She currently has no acute concerns but has been feeling hopeless, has a poor appetite, difficulty with concentration, and trouble with sleep. She says that she has poor self-esteem and that her symptoms have been occurring for the past 3 years. She has had moments where she felt better, but it lasted a few weeks out of the year. She currently lives alone and does not pursue romantic relationships because she feels she is not attractive. She has a past medical history of asthma. Her mother is alive and healthy. Her father committed suicide and suffered from major depressive disorder. On physical exam, the patient has a gloomy demeanor and appears restless and anxious. Which of the following is the most likely diagnosis?

Disruptive mood dysregulation disorder

A 38-year-old woman comes to the physician for a follow-up visit. She has a 2-year history of depressed mood and fatigue accompanied by early morning awakening. One week ago, she started feeling a decrease in her need for sleep and now feels rested after about 5 hours of sleep per night. She had two similar episodes that occurred 6 months ago and a year ago, respectively. She reports increased energy and libido. She has a 4-kg (8.8-lb) weight loss over the past month. She does not feel the need to eat and says she derives her energy ""from the universe"". She enjoys her work as a librarian. She started taking fluoxetine 3 months ago. On mental exam, she is alert and oriented to time and place; she is irritable. She does not have auditory or visual hallucinations. Physical examination shows no abnormalities. Which of the following is the most likely diagnosis?

Medication-induced bipolar disorder

Mood disorder epidemiology for USMLE Step 3: High-Yield Psychiatry Lessons

MDD Epidemiology - The Common Cold

Lifetime Prevalence: ~15-25% in the US, making it a very common psychiatric illness.
Gender: ↑ in women (2:1 ratio vs. men), a consistent finding across various cultures.
Age of Onset: Mean age is ~30 years, but it can present at any point in the lifespan.
Risk Factors:
- No definitive correlation with socioeconomic status or race.
- High prevalence in primary care settings (~10%).
Comorbidities: Frequently co-occurs with anxiety disorders, substance use disorder, and panic disorder.

⭐ Major Depressive Disorder is a leading cause of disability worldwide for individuals aged 15-44.

Prevalence of mental disorders by type

Bipolar Disorder Epidemiology - Seesaw Stats

Lifetime Prevalence (US): ~4.4% for the full bipolar spectrum.
- Bipolar I: ~1%
- Bipolar II: ~1.1%
Gender Seesaw:
- Bipolar I: Slightly more common in males (M:F ≈ 1.1:1).
- Bipolar II: More common in females (M:F ≈ 1:1.2).
Age of Onset: Mean age is 25 years; onset can occur from childhood to late life.

⭐ The lifetime risk of suicide in individuals with bipolar disorder is estimated to be 15-20 times higher than that of the general population.

Other Mood Disorders - The Long-Haul Blues

Persistent Depressive Disorder (Dysthymia)
- Chronic depressed mood for at least 2 years (≥1 year for children/adolescents).
- Requires ≥2 of the following: poor appetite/overeating, insomnia/hypersomnia, low energy, low self-esteem, poor concentration, or feelings of hopelessness.
- 📌 Mnemonic: "2 years, 2 symptoms."
Cyclothymic Disorder
- A chronic, fluctuating mood disturbance for at least 2 years (≥1 year for children/adolescents).
- Involves numerous periods with hypomanic symptoms and periods with depressive symptoms that do not meet criteria for a major depressive episode.

⭐ Patients with cyclothymia have a 15-50% lifetime risk of developing Bipolar I or Bipolar II disorder.

Risk Factors & Comorbidity - The Usual Suspects

Genetics: Strongest predictor. Risk ↑ significantly if a 1st-degree relative is affected.
Neurobiology: Dysregulation of serotonin, norepinephrine, dopamine.
Psychosocial: Adverse childhood experiences (ACEs), chronic stress, lack of social support.
Female Sex: Major Depressive Disorder (MDD) is ~2x more common in women. Bipolar I Disorder has a 1:1 male-to-female ratio.

Biopsychosocial Model of Health

Common Comorbidities:
- Anxiety Disorders (e.g., GAD, Panic Disorder)
- Substance Use Disorders
- Personality Disorders (esp. Borderline)

⭐ A lifetime history of an anxiety disorder is present in over 50% of patients with MDD.

Major Depressive Disorder (MDD) has a lifetime prevalence of 15-25% and is 2x more common in women.

Bipolar I Disorder affects ~1% of the population, with an equal prevalence in men and women.

Family history is the strongest risk factor for both MDD and Bipolar Disorder.

High rates of comorbidity with anxiety disorders and substance use disorders.

Mood disorders are a leading cause of disability worldwide.

Significant suicide risk: up to 15% in Bipolar Disorder.

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Mood disorder epidemiology