A mother brings her 3-year-old son to the doctor because she is worried that he might be harming himself by constantly banging his head on the wall. He has been exhibiting this behavior for a few months. She is also worried because he has started to speak less than he used to and does not respond when his name is called. He seems aloof during playtime with other children and seems to have lost interest in most of his toys. What is the most likely diagnosis?

Attention deficit hyperactivity disorder

A 20-year-old female presents to student health at her university for excessive daytime sleepiness. She states that her sleepiness has caused her to fall asleep in all of her classes for the last semester, and that her grades are suffering as a result. She states that she normally gets 7 hours of sleep per night, and notes that when she falls asleep during the day, she immediately starts having dreams. She denies any cataplexy. A polysomnogram and a multiple sleep latency test rule out obstructive sleep apnea and confirm her diagnosis. She is started on a daytime medication that acts both by direct neurotransmitter release and reuptake inhibition. What other condition can this medication be used to treat?

Attention-deficit hyperactivity disorder

A 15-year-old girl is brought into her pediatrician's office by her mother because the mother thinks her daughter has attention issues. The mother explains that her daughter started high school four months ago and had lackluster grades in a recent progress report despite having earned consistent top marks in middle school. The mother complains that her daughter never talks to her at home anymore. The patient yells at her mother in the exam room, and the mother is escorted out of the room. The patient scoffs that her mother is so overbearing, ruining her good days with criticism. She begins to chew gum and states that she hates hanging out with the girls on the cheerleading squad. She denies experiencing physical abuse from anyone or having a sexual partner. She has seen kids smoke marijuana underneath the football field bleachers, but does not go near them and denies smoking cigarettes. She denies any intention to harm herself or others, thinks her grades went down because her teachers are not as good as her middle school teachers, and states she thinks she learns best by watching explanations through online videos. What is the most likely diagnosis?

Attention deficit hyperactivity disorder

Antisocial personality disorder

A 14-year-old boy is brought to a child psychiatry office by his father, who is concerned about his grades and teachers’ comments that he has “problems focusing.” He has a B- average. The boy's teachers in math, social studies, and English say that he often appears to not be listening in class, instead talking to classmates, making jokes, and blurting out incorrect answers. He typically turns in his homework late or not at all. During other classes (band and science, which he enjoys), none of these behaviors are observed. At home, he enjoys playing chess and reads comic and fiction books for hours without pause. His father describes him as calm and organized at home. Formal testing reveals an intelligence quotient (IQ) of 102. Which of the following is the most likely explanation for this patient’s grades?

Attention deficit hyperactivity disorder (ADHD)

A 28-year-old male presents to his primary care physician with complaints of intermittent abdominal pain and alternating bouts of constipation and diarrhea. His medical chart is not significant for any past medical problems or prior surgeries. He is not prescribed any current medications. Which of the following questions would be the most useful next question in eliciting further history from this patient?

"Can you tell me more about the symptoms you have been experiencing?"

"Does the diarrhea typically precede the constipation, or vice-versa?"

"Is the diarrhea foul-smelling?"

"Please rate your abdominal pain on a scale of 1-10, with 10 being the worst pain of your life"

"Are the symptoms worse in the morning or at night?"

A 9-year-old boy is brought to a pediatric psychologist by his mother because of poor academic performance. The patient’s mother mentions that his academic performance was excellent in kindergarten and first grade, but his second and third-grade teachers complain that he is extremely talkative, does not complete schoolwork, and frequently makes careless mistakes. They also complain that he frequently looks at other students or outside the window during the class and is often lost during the lessons. At home, he is very talkative and disorganized. When the pediatrician asks the boy his name, he replies promptly. He was born at full term by spontaneous vaginal delivery. He is up-to-date on all vaccinations and has met all developmental milestones on time. A recent IQ test scored him at 95. His physical examination is completely normal. When he is asked to read from an age-appropriate children’s book, he reads it fluently and correctly. Which of the following is the most likely diagnosis in this patient?

Attention-deficit/hyperactivity disorder

An 11-year-old boy’s parents brought him to a psychologist upon referral from the boy’s school teacher. The boy frequently bullies his younger classmates despite having been punished several times for this. His mother also reported that a year prior, she received complaints that the boy shoplifted from local shops in his neighborhood. The boy frequently stays out at night despite strict instructions by his parents to return home by 10 PM. Detailed history reveals that apart from such behavior, he is usually not angry or irritable. Although his abnormal behavior continues despite warnings and punishments, he neither argues with his parents nor teachers and does not display verbal or physical aggression. Which of the following is the most likely diagnosis?

Attention-deficit/hyperactivity disorder, hyperactivity-impulsivity type

Disruptive mood dysregulation disorder

Intermittent explosive disorder

A 28-year-old woman is brought to the emergency department by her friends. She is naked except for a blanket and speaking rapidly and incoherently. Her friends say that she was found watering her garden naked and refused to put on any clothes when they tried to make her do so, saying that she has accepted how beautiful she is inside and out. Her friends say she has also purchased a new car she can not afford. They are concerned about her, as they have never seen her behave this way before. For the past week, she has not shown up at work and has been acting ‘strangely’. They say she was extremely excited and has been calling them at odd hours of the night to tell them about her future plans. Which of the following drug mechanisms will help with the long-term management this patient’s symptoms?

Inhibition of inositol monophosphatase and inositol polyphosphate 1-phosphatase

Increase the concentration of dopamine and norepinephrine at the synaptic cleft

Modulate the activity of gamma-aminobutyric acid receptors

Acts as an antagonist at the dopamine, serotonin and adrenergic receptors

Inhibit the reuptake of norepinephrine and serotonin from the presynaptic cleft

A 21-year-old man presents to the clinic complaining of feeling tired during the day. He is concerned as his grades in school have worsened and he does not want to lose his scholarship. Upon further questioning, the patient describes frequently experiencing a dreamlike state before falling asleep and after waking up. He also has frequent nighttime awakenings where he finds himself unable to move. He denies snoring. The patient does not drink alcohol or abuse any other drugs. The patient's BMI is 21 kg/m2, and his vital signs are all within normal limits. What is this patient's diagnosis?

Delayed sleep phase syndrome (DSPS)

ADHD subtypes and diagnostic criteria for USMLE Step 2 CK: High-Yield Psychiatry Lessons

ADHD Overview - The Brain's Busy Bees

Core Features: Persistent pattern of inattention and/or hyperactivity-impulsivity that interferes with functioning or development.
Diagnostic Criteria:
- Multiple symptoms present before age 12.
- Symptoms occur in ≥2 settings (e.g., home, school).
- Clear evidence of functional impairment.
Subtypes:
- Predominantly Inattentive
- Predominantly Hyperactive-Impulsive
- Combined Presentation

⭐ High-Yield: ADHD symptoms persist into adulthood in up to 60% of cases, often co-occurring with anxiety, depression, and substance use disorders.

How ADHD Affects the Brain

ADHD Subtypes - Not Just Fidgeting

Predominantly Inattentive (≥6/9 symptoms): Difficulty focusing, disorganized, easily distracted, and forgetful. Often overlooked, especially in girls.
Predominantly Hyperactive-Impulsive (≥6/9 symptoms): Classic restlessness, impulsivity, interrupting others, and being constantly "on the go."
Combined Type: Meets criteria for both inattention and hyperactivity-impulsivity for the past 6 months.

Core Diagnostic Criteria:

Multiple symptoms present before age 12.
Impairment in ≥2 settings (e.g., home, school, work).
Symptoms interfere with functioning.

⭐ In adults, hyperactivity often manifests as internal restlessness or being overworked, while inattention remains prominent, causing significant functional impairment.

DSM-5 Criteria - The Diagnostic Rules

Pattern of inattention and/or hyperactivity-impulsivity that interferes with functioning or development.
Core Requirements: 📌 A-D-H-D
- Age: Several symptoms present before age 12.
- Duration: Symptoms persist for ≥6 months.
- Habitat (Settings): Symptoms present in ≥2 settings (e.g., home, school, work).
- Dysfunction: Clear evidence of interference with social, academic, or occupational functioning.

⭐ For individuals age 17 and older, the DSM-5 requires meeting only 5 symptoms from a category, rather than the 6 required for younger children. This reflects the developmental trajectory of ADHD symptoms.

Differential Dx - Is It Really ADHD?

Medical Conditions:
- Hyperthyroidism (check TSH)
- Obstructive Sleep Apnea (snoring, daytime sleepiness)
- Hearing/vision impairment
- Lead toxicity
- Fetal alcohol syndrome
Psychiatric Disorders:
- Anxiety/Depression: Poor concentration is secondary to worry/anhedonia.
- Bipolar Disorder: Symptoms are episodic, with elevated mood/grandiosity.
- Oppositional Defiant/Conduct Disorder: Core is intentional rule-breaking.
- Specific Learning Disability: Difficulties confined to academics.

⭐ In Bipolar Disorder, hyperactivity is episodic and mood-congruent (mania), unlike the chronic, pervasive pattern seen in ADHD.

ADHD diagnosis requires ≥6 symptoms of inattention and/or hyperactivity-impulsivity for ≥6 months, present before age 12.

For adults (age ≥17), the threshold is lowered to ≥5 symptoms.

Symptoms must be present in ≥2 settings (e.g., home, school) and cause significant functional impairment.

Three presentations: predominantly inattentive, predominantly hyperactive-impulsive, and combined.

Always consider and rule out other conditions like learning disorders, anxiety, or mood disorders.

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