DSM-5-TR Differentials: The Time Criteria That Decide the Answer

Read a set of PMHNP diagnostic items back to back and a pattern appears. The symptom list in the stem is usually compatible with two or three diagnoses. The thing that makes exactly one of them correct is almost always a number: how long this has been going on, how long ago it started, how many days the episode lasted.

This is not an accident of question writing. It is how the DSM-5-TR is built. Duration criteria are what separate closely related disorders, so duration criteria are what a well-constructed item tests.

The durations that separate disorders

Duration criteria, thresholds and specifiers are revised between editions and text revisions. Verify anything you intend to memorise against the current DSM text rather than a summary table, including this one.

The pairs that get confused

Bipolar I versus bipolar II

Bipolar I requires a manic episode. That is the whole distinction - a depressive episode is common but not required. Bipolar II requires a hypomanic episode and at least one major depressive episode, and the presence of a full manic episode at any point moves the diagnosis to bipolar I permanently. Severity of the depression does not decide it.

Schizoaffective disorder versus a mood disorder with psychotic features

The discriminator is whether psychosis occurs in the absence of a mood episode. In schizoaffective disorder there is a period of at least two weeks of psychotic symptoms without prominent mood symptoms, alongside mood episodes that are present for the majority of the illness. In major depression or bipolar disorder with psychotic features, the psychosis occurs only during mood episodes.

Delirium versus dementia versus depression in an older adult

This triad appears constantly and is decided on onset and course. Delirium is acute, fluctuating, and marked by disturbed attention and awareness - and it is a medical emergency requiring a search for a cause. Major neurocognitive disorder is insidious and progressive with relatively preserved attention early on. Depression in older adults can present with cognitive complaints and is characterised by prominent low mood or anhedonia, with the patient often highlighting their deficits rather than concealing them.

Any stem with an abrupt change in attention and consciousness in an older adult is a delirium workup question until proven otherwise, whatever else is in the history.

Panic disorder versus panic attacks

Panic attacks occur across many disorders and are a specifier, not a diagnosis. Panic disorder requires recurrent unexpected attacks plus a period of persistent concern about further attacks or a significant maladaptive change in behaviour.

Obsessive-compulsive disorder versus generalised anxiety

Worries in generalised anxiety disorder are about real-life concerns and are experienced as excessive but not alien. Obsessions are intrusive, unwanted and usually recognised as products of one's own mind, and are typically followed by compulsions performed to reduce distress.

What you rule out before you diagnose

A substantial share of diagnostic items are really testing whether you exclude the other explanations first. Before a primary psychiatric diagnosis is the answer, the exam wants substance and medication effects considered, another medical condition considered, and - in older adults especially - delirium considered.

Thyroid dysfunction, vitamin B12 deficiency, infection, medication effects including steroids and anticholinergics, substance intoxication and withdrawal, and sleep disorders all appear in stems as the actual cause of a psychiatric-looking presentation. If a stem goes out of its way to mention a new medication, a recent illness or a laboratory value, it is telling you something.

Culture, development and context

ANCC items regularly test whether a described experience is a symptom or a norm. A belief or practice that is congruent with a patient's cultural or religious community, and that does not cause distress or impairment, is not in itself evidence of a disorder. The cultural formulation approach - asking what the patient calls the problem, what they believe causes it, and what they expect from treatment - is frequently the correct answer to "what is the best initial response".

Developmental context matters similarly. Behaviour that is age-appropriate in a four-year-old is not age-appropriate in a fourteen-year-old, and bereavement, adjustment reactions and normal developmental variation all appear as distractors against a full diagnosis.

How to drill this

Make one card per pair, not one card per disorder. On the front, the two diagnoses that get confused; on the back, the single feature that separates them. Twenty pairs covers most of what the exam will ask, and pairs are far easier to retrieve under pressure than a sixty-item criteria list.