A 5-year-old girl is brought to the physician because her mother has found her to be inattentive at home and has received multiple complaints from her teachers at school. She does not complete her assignments and does not listen to her teachers' instructions. She refuses to talk to her parents or peers. Her mother says, “She ignores everything I say to her!” She prefers playing alone, and her mother reports that she likes playing with 5 red toy cars, repeatedly arranging them in a straight line. She avoids eye contact with her mother and the physician throughout the visit. Physical and neurological examination shows no abnormalities. Which of the following is the most likely diagnosis?

Attention deficit hyperactivity disorder

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 10-year-old boy is brought to the physician by his parents because they are concerned about his “strange behavior”. The parents state that he has always been a lonely kid without many friends, but recently he has been having behavioral problems that seem to be unprovoked and are occurring more frequently. The child throws tantrums for no reason and does not respond to punishment or reward. He also has a “strange obsession” with collecting rocks that he finds on his way to and from school to the point where his room is filled with rocks. He plays alone in his room, lining the rocks up, organizing them by size, shape, or color, and he will randomly bark or make high-pitched noises without provocation. His teachers say he daydreams a lot and is very good at art, being able to recreate his favorite cartoon characters in great detail. On physical assessment, the patient does not make eye contact with the physician but talks incessantly about his rock collection. The child’s grammar and vocabulary seem normal but his speech is slightly labored, and he can’t seem to tell that the physician is not really interested in hearing about his rock collection. Which of the following is the most likely diagnosis?

Attention deficit hyperactivity disorder

A 4-year-old girl is brought to the pediatrician by her parents after her mother recently noticed that other girls of similar age talk much more than her daughter. Her mother reports that her language development has been abnormal and she was able to use only 5–6 words at the age of 2 years. Detailed history reveals that she has never used her index finger to indicate her interest in something. She does not enjoy going to birthday parties and does not play with other children in her neighborhood. The mother reports that her favorite “game” is to repetitively flex and extend the neck of a doll, which she always keeps with her. She is sensitive to loud sounds and starts screaming excessively when exposed to them. There is no history of delayed motor development, seizures, or any other major illness; perinatal history is normal. When she enters the doctor’s office, the doctor observes that she does not look at him. When he gently calls her by her name, she does not respond to him and continues to look at her doll. When the doctor asks her to look at a toy on his table by pointing a finger at the toy, she looks at neither his finger nor the toy. The doctor also notes that she keeps rocking her body while in the office. Which of the following is an epidemiological characteristic of the condition the girl is suffering from?

This condition is 4 times more common in boys than girls.

There has been a steady decline in prevalence in the United States over the last decade.

There is an increased risk if the mother smoked during pregnancy.

There is an increased risk with low prenatal maternal serum vitamin D level.

There is an increased incidence if the mother gives birth before 25 years of age.

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?"

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

Autism spectrum disorder diagnostic criteria for USMLE Step 2 CK: High-Yield Psychiatry Lessons

ASD Diagnostic Criteria - The Two Pillars

A. Persistent Deficits in Social Communication & Interaction (all 3 criteria must be met):
- Deficits in social-emotional reciprocity (e.g., failure of back-and-forth conversation).
- Deficits in nonverbal communicative behaviors (e.g., poor eye contact, lack of facial expressions).
- Deficits in developing, maintaining, and understanding relationships.
B. Restricted, Repetitive Patterns of Behavior, Interests, or Activities (at least 2 of 4 criteria):
- Stereotyped or repetitive motor movements, use of objects, or speech.
- Insistence on sameness, inflexible adherence to routines.
- Highly restricted, fixated interests abnormal in intensity or focus.
- Hyper- or hyporeactivity to sensory input.

⭐ Symptoms must be present in the early developmental period, but may not fully manifest until social demands exceed limited capacities.

*Persistent deficits in social communication and interaction across multiple contexts, manifested by all 3 of the following (currently or by history):

Deficits in social-emotional reciprocity
- Abnormal social approach & failure of back-and-forth conversation.
- Reduced sharing of interests, emotions, or affect.
- Failure to initiate or respond to social interactions.
Deficits in nonverbal communicative behaviors
- Poorly integrated verbal & nonverbal communication.
- Abnormalities in eye contact, body language, or gestures.
- Lack of facial expressions.
Deficits in developing, maintaining, & understanding relationships
- Difficulty adjusting behavior to suit social contexts.
- Difficulties in sharing imaginative play or making friends.

⭐ All 3 deficits in Criterion A must be met for diagnosis. Severity is specified based on the level of support required.

Criterion B - Repetitive Behavior Patterns

Restricted, repetitive patterns of behavior, interests, or activities, requiring at least two of the following, currently or by history:
- Stereotyped/Repetitive Behaviors: Includes repetitive motor movements, use of objects, or speech (e.g., echolalia, lining up toys, hand-flapping).
- Insistence on Sameness/Routines: Inflexible adherence to specific, nonfunctional routines or rituals; extreme distress at small changes.
- Restricted/Fixated Interests: Highly restricted, fixated interests that are abnormal in intensity or focus (e.g., strong preoccupation with unusual objects).
- Sensory Issues: Hyper- or hyporeactivity to sensory input or unusual interest in sensory aspects of the environment (e.g., indifference to pain, adverse response to specific sounds or textures).

⭐ High-Yield: For diagnosis, at least two of these four criteria must be met. Symptoms must be present in the early developmental period.

📌 Mnemonic: SIRS (Stereotyped, Insistence, Restricted, Sensory).

Examples of Restricted and Repetitive Behaviors in ASD

Severity & Specifiers - The Fine Print

Severity is based on levels of required support across two domains: Social Communication & Restricted/Repetitive Behaviors.
Specifiers add crucial detail:
- With/without intellectual impairment
- With/without language impairment
- Associated with a known medical, genetic, or environmental factor
- Associated with another neurodevelopmental, mental, or behavioral disorder
- With catatonia

⭐ Severity levels can change over time and vary by context. A child might function at Level 1 at home but require Level 2 support at school.

High-Yield Points - ⚡ Biggest Takeaways

Persistent deficits in social communication and interaction across multiple contexts.

Restricted, repetitive patterns of behavior, interests, or activities (RRBs).

Symptoms must be present in the early developmental period.

Causes clinically significant impairment in social or occupational functioning.

Not better explained by intellectual disability or global developmental delay.

Severity is specified based on level of support needed (Levels 1, 2, or 3).

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