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Know Thy Shelf: PSYCH!

In my humble opinion, one of the most interesting clerkship rotations we get to partake in is psychiatry. It is usually the place where some of the more unexpected things happen, such as your bipolar patient suddenly stripping naked and doing laps around the unit. That’s certainly more enthralling than, say, when your DKA patient’s anion gap closed, no?

Either way, whether you love or hate psychiatry, you will have to take a Shelf in this subject, and it will behoove you to do well. Plus, no matter what field you go into, remembering to check QTc’s on your patients on seroquel and knowing how to deal with your delirious patients will come in handy — so learn this once and learn it right.

Start Strong

Right before the clock started on my first Shelf exam, the proctor gave us an invaluable piece of information. This tip was so helpful, it almost felt like cheating when we got to the Psych Shelf. It is also wildly helpful for USMLE questions. She told us to pay particular attention to the first sentence in each vignette. She said the information included therein would get us 80% of the way to the answer choice, and she was right.

This becomes especially important for the Psychiatry Shelf, whose vignettes are often huge blocks of text that can take over a minute just to read through. You should be able to slash your differential (and number of possible answer choices) in half after digesting this first sentence.

For instance: “An elderly lady is brought in by her husband for 2 hours of agitation and confusion.” Go ahead and strike major depressive disorder, Alzheimer’s dementia, and vascular dementia off your list. While it is tempting to label an older, confused patient as being demented, that is a chronic problem. Knowing that this presentation is acute should make you search for an acute cause of confusion… something more like an acute systemic illness (e.g. UTI, electrolyte abnormality, meningoencephalitis). This leads us into the next point:

For how long has this been going on?

So many of the psychiatric diagnoses are dependent solely on timeframe. Differentiating between brief psychotic disorder, schizophreniform disorder, and schizophrenia is done purely on the basis of how long the patient has been suffering from symptoms. Even if our 18 year old male is withdrawing from society, giving up on self care, experiencing visual and auditory hallucinations, and floridly delusional, if he’s only felt this way for 10 days, we can forget about schizophrenia. It is not the severity, but merely the time course of symptoms that helps separate these diagnoses.

The same holds true for acute stress disorder and posttraumatic stress disorder (PTSD). Patients will be experiencing the same stresses, nightmares, and flashbacks, but if is going on for less than a month, it can’t be PTSD. Another intertwined couple: conduct disorder and antisocial personality disorder. When the patient turns 18, the former becomes the latter. Getting into the habit of compartmentalizing these diseases that are basically the same problem, but only differ because of duration will make your studying easier, minimizing the number of novel conditions to know.

Borrow from other disciplines.

To say that this test is purely one of psychiatric conditions is a misnomer. To make many of these diagnoses requires the absence of a medical condition to explain the patient’s change in behavior or mental status. Consider these scenarios:

Is your kooky, up-all-night-online-shopping, flight of ideas screaming, hyperexcitable, middle-aged lady exhibiting signs of bipolar disorder? Or is she just hopped up on the prednisone her PCP prescribed for her furious poison ivy?

Is the patient with headache, fatigue, nausea, vomiting, constipation, abdominal pain, lightheadedness, and palpitations suffering from somatization disorder? Or does she have a legitimate small bowel obstruction?

Ultra-classic though fully psychiatric: The 72-year old grandpa who is getting forgetful, having trouble with balancing the checkbook, becoming withdrawn, occasionally lashing out at family members whose names he can’t recall… Is this a slow decline into dementia? Or is it just pseudodementia (depression)?

Take-home point: It is essential to rule out organic pathology before giving patients these diagnoses that can’t otherwise be explained by another medical condition.

Know Normal

In our neverending search for pathologies, it is easy to overlook a patient who is not sick. This is particularly true when concerned parents can make us question the proper development of their child. When it comes to childhood development, don’t be quick to label a child as lacking in a particular category just because they are a few months later than the 50th percentile timeframe. That is, it is permissible to take first steps at 14 months instead of the benchmark 12. The same holds true for first words. Along those lines, the 3 year-old who can’t sit still and is easily distracted probably doesn’t have ADHD so much as they have toddler-iasis. As for the 16 year-old son whose mom is concerned that he tried a single beer or marijuana cigarette… he doesn’t have a drug problem (yet). He is in a normal phase of adolescent experimentation.


Just because psych feels different from other medical disciplines doesn’t mean that it is not chock full of in-depth pharmacology. When it comes time to internalize the countless neuroleptics, anti-epileptic drugs, and various classes of antidepressants, the most important thing to remember is their side effects. So many drugs can be used first line, and the choice will often come down to knowing what side effects you are trying to avoid. Here are some to get you started:

  • All antipsychotics – QT interval prolongation
  • SSRI – sexual dissatisfaction (can try bupropion instead)
  • Clozapine – Very effective but can cause agranulocytosis! Check weekly CBCs!
  • Olanzapine – Most likely atypical antipsychotic to cause weight gain
  • Tricyclic antidepressants – Anticholinergic side effects (think elderly urinary retention)

Lastly, when in doubt, start with an SSRI. They are first line for major depressive disorder, panic disorder, obsessive compulsive disorder, generalized anxiety disorder, bulimia nervosa, and even premature ejaculation.


Medical student populace at large: what questions do you have about this long and often grueling shelf exam?



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