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NP CHRONICLES Clinical Deep Dive |
 When “Depression” Isn’t Depression Three medical mimics primary
care and NP clinicians miss — and how to catch them |
A PHQ-9 of 17. A tearful patient
who “just doesn’t feel like myself.” It’s tempting to reach straight for an
SSRI — and often that’s exactly right. But depressive syndromes are the final
common pathway for a surprising number of non-psychiatric conditions, and
treatment-resistant “depression” is one of the more common ways those
conditions announce themselves in a primary care visit.
Jeffrey Rado, MD, MPH, DFAPA
(Northwestern Feinberg School of Medicine) built a CME talk around exactly this
problem, using three composite cases to walk through the medical mimics most
likely to slip past a busy PCP or NP: obstructive sleep apnea, vitamin B12
deficiency, and medication-induced mood change. Below is a working summary of
that talk, reorganized case-by-case with the diagnostic reasoning made explicit
— useful both for your own practice and for board review.
Case 1: Brenda —
“Treatment-Resistant” Depression
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Case from Practice Brenda, 51, presents with 6
months of low mood, anhedonia, exhaustion, non-restorative sleep, and
irritability. Sertraline was titrated from 50 mg to 100 mg six weeks ago with
little benefit; an earlier duloxetine trial also failed. She has occasional
stress headaches, low libido, and nocturia she attributes to evening fluids. PMHx: hypertension, seasonal
allergies. Mother has hypothyroidism and depression. Vitals: BP 141/82, BMI
34.3. PHQ-9 = 17. |
Brenda’s CMP, CBC, TSH, and B12
all come back normal, and her husband confirms no snoring and 8–9 hours of
sleep a night — on paper, nothing points to a sleep disorder. Her STOP-BANG
score is 4 (intermediate risk). A follow-up call adds occasional palpitations.
Sleep medicine is consulted anyway, and polysomnography confirms obstructive
sleep apnea. Four months after starting CPAP, her PHQ-9 drops from 17 to 6.
Why This Gets Missed
The classic OSA triad — snoring,
witnessed apneas, daytime sleepiness — is a poor fit for how the disease
actually presents in women. Women with OSA more often report fatigue, insomnia,
morning headaches, and mood symptoms, and the absence of snoring doesn’t rule
the diagnosis out: upper airway resistance syndrome can fragment sleep and
produce depressive symptoms without any audible snoring at all.
Clinically, OSA reproduces the
depression phenotype through several overlapping mechanisms:
•
Low mood and anhedonia from
sleep fragmentation and intermittent hypoxia disrupting mood-regulating
circuits
•
Fatigue and daytime sleepiness
misread as psychomotor retardation or neurovegetative symptoms
•
Impaired concentration and
memory from nocturnal hypoxemia — the “brain fog” of depression
•
Irritability and emotional
dysregulation from impaired prefrontal function
•
Nocturia — often chalked up to
fluid intake, but can reflect atrial natriuretic peptide release triggered by
intrathoracic pressure swings during obstructive events
Worth remembering: several
medications commonly prescribed alongside a depression diagnosis can worsen OSA
and quietly perpetuate it. Benzodiazepines and opioids relax upper airway
muscles and blunt respiratory drive; atypical antipsychotics (olanzapine,
quetiapine, risperidone) worsen OSA through weight gain and a separate,
weight-independent effect on upper airway muscle tone. Sedating antihistamines
and low-dose antipsychotics used for sleep can mask the very symptoms —
fragmented sleep, daytime sleepiness — that would otherwise prompt an OSA
work-up.
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Clinical Pearls •
Treatment-resistant depression
after two adequate antidepressant trials should always prompt consideration
of undiagnosed OSA, regardless of body habitus or reported sleep complaints. •
A normal STOP-BANG or a
negative snoring history does not exclude OSA, particularly in women. •
Bruxism, nocturia, GERD, and
palpitations are underrecognized nocturnal clues to sleep-disordered
breathing. |
Case 2: Ken — New-Onset
Depression at 68
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Case from Practice Ken, 68, has type 2 diabetes
and GERD and presents with three months of sad mood, fatigue, anhedonia,
increasing forgetfulness, irritability, and a passive death wish — with no
prior psychiatric history. He reports foot tingling treated with gabapentin and
nearly fell two months ago. He has followed a plant-based diet for 2–3 years
to help control his diabetes. Current meds: pantoprazole,
metformin, sitagliptin, gabapentin. |
CMP, CBC, and TSH are
unremarkable. Sertraline, titrated from 50 mg to 100 mg, produces minimal
benefit. A vitamin B12 level comes back at 201 pg/mL — borderline low. After
repletion, Ken reports his depression starting to lift at follow-up.
Why This Gets Missed
Depression is the most common
psychiatric manifestation of B12 deficiency, driven by disrupted one-carbon
metabolism and impaired neurotransmitter synthesis: B12 is a required cofactor
in converting homocysteine to methionine, which forms SAMe — itself required
for synthesizing dopamine, serotonin, and norepinephrine. Anxiety tracks with
low B12 levels as well. Psychiatric symptoms from B12 deficiency can precede
the textbook findings of anemia and spinal cord disease, which is exactly why
relying on a normal CBC to “clear” B12 status is a mistake.
Ken’s case stacks three separate
risk factors for deficiency in one patient:
•
Metformin use — the ADA
recommends periodic B12 assessment, since metformin interferes with B12
absorption
•
Chronic PPI use — gastric acid
suppression reduces B12 absorption from food
•
A plant-based diet — B12 is
found almost exclusively in animal products
Guidelines back up routinely
checking B12: an NEJM review on primary care depression recommends B12 and
folate as initial screening labs for any patient with depressive symptoms, and
the 2022 VA/DoD Clinical Practice Guideline for major depressive disorder
specifically calls for ruling out B12 deficiency as a secondary cause. Yield is
highest in patients age 75 and up, those on metformin for more than four months
or a PPI/H2 blocker for more than a year, those on vegan or strict vegetarian
diets, and anyone with neuropsychiatric features beyond mood — paresthesias,
cognitive change, gait disturbance, or fatigue out of proportion to the degree
of depression.
One nuance worth flagging for
patients and colleagues alike: repletion doesn’t work on a single timeline.
Mood and energy typically improve within weeks; cognition takes weeks to
months; neuropathy takes months and, if repletion is delayed, may not fully
resolve.
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Clinical Pearls •
New-onset depression in an
older adult, with any cognitive or neurological symptoms, or that isn’t
responding to an antidepressant, warrants a B12 check. •
Metformin, PPIs/H2 blockers,
and plant-based diets are the three risk factors to actively screen for. •
A “normal” B12 in the 200s
pg/mL range is borderline, not reassuring — correlate with symptoms before
writing it off. |
Case 3: Ashley — Depression That
Tracks a New Prescription
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Case from Practice Ashley, 41, has major
depression well controlled on escitalopram 10 mg for 18 months and is
functioning well, working full time. She was hospitalized at an outside
facility for seizures two months ago and started on new medications she can’t
name. The hospitalization and new diagnosis have been “very hard” on her —
she is withdrawing socially, wondering if she’s getting depressed again, and
not enjoying time with her kids. Her husband reports she was
coping reasonably well until she became more irritable and down following a
dose increase of the new medication two weeks ago. A nurse reaches Ashley at
home and learns the new medication is levetiracetam. |
Why This Gets Missed
It’s easy — and reasonable — to
read Ashley’s mood change as a psychological reaction to a frightening new
diagnosis. But the timeline is the tell: symptoms tracked a specific medication
start and then worsened with a dose increase two weeks later. That temporal and
dose-response relationship, on top of new irritability and emotional volatility
in a previously stable patient, points toward levetiracetam-induced mood change
rather than a purely reactive depression.
Levetiracetam binds synaptic
vesicle protein 2A (SV2A), decreasing glutamate release; the resulting blunted
limbic synaptic signaling is thought to lower dopamine and serotonin tone — a
plausible mechanism for the irritability and depressive symptoms seen in a
subset of patients. Risk is highest with a history of depression, anxiety, or
emotional lability; prior antidepressant use or psychiatric hospitalization;
temporal lobe epilepsy; traumatic brain injury or a structural brain lesion;
rapid titration to full dose (under two weeks); high dosing (1000–1500 mg BID);
and concurrent CNS-active medications. Early warning signs — new irritability,
emotional reactivity, sleep disturbance, social withdrawal, subtle mood
flattening — typically surface in the first one to three weeks and, if present,
are highly predictive of the depression that follows.
Levetiracetam is far from the
only offender. Interferon-alfa, interleukin-2, and high-dose corticosteroids
(especially above 40 mg prednisone) carry the highest risk of
medication-induced mood change; topiramate and phenobarbital sit alongside
levetiracetam in that same tier. Combined oral contraceptives, GnRH analogs
like leuprolide, and montelukast carry moderate risk; beta blockers and
isotretinoin remain controversial. Even medications prescribed to manage sleep
and anxiety — gabapentin and pregabalin (long-term depression and suicidality
risk), dual orexin receptor antagonists, and benzodiazepines — can move the
needle on mood. As Rado puts it, essentially any psychotropic carries some
risk.
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A Necessary Nuance No medication cleanly causes
classic major depressive disorder — what these drugs produce are depressive
syndromes layered on top of whatever is already driving risk. In Ashley’s
case, the underlying illness (new-onset epilepsy, the trauma of a first seizure
and hospitalization) is a plausible contributor in its own right, roughly as
strong a driver as the medication itself. Before attributing a mood change
entirely to a drug, walk through four questions: Does the timing fit (onset
within weeks to months of the start)? Is there a dose-response relationship?
Does it improve off the drug and recur on re-exposure? And is there a
competing explanation — illness burden, sleep disruption, inflammation — that
fits just as well? |
Clinical Bottom Line
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Clinical Bottom Line •
Treatment-resistant depression
deserves a STOP-BANG and a low threshold for sleep medicine referral — don’t
let a negative snoring history or a lean body habitus close that door,
especially in women. •
Check vitamin B12 in any
patient with new-onset or atypical depression, particularly those 75 and
older, on metformin or a PPI/H2 blocker long-term, following a plant-based
diet, or with neuropsychiatric symptoms beyond mood. •
Always ask about new
medications and dosage changes at every visit — timing, dose-response, and
rechallenge history are the fastest ways to separate a medication effect from
a primary mood disorder. |
Board Prep: What to Remember
A few facts from this topic that
tend to show up on certification and recertification exams:
1.
In women, OSA more often
presents with fatigue, insomnia, morning headaches, and mood symptoms than the
classic snoring/witnessed-apnea/daytime-sleepiness triad.
2.
Metformin (via B12
malabsorption), chronic PPI/H2 blocker use, and vegan/vegetarian diets are the
three classic risk factors for B12 deficiency worth screening for in a
depressed patient.
3.
B12 repletion improves
mood/energy within weeks, cognition within weeks to months, and neuropathy over
months — and neuropathy may only partially resolve if treatment is delayed.
4.
Highest-risk medications for
drug-induced depression: interferon-alfa, interleukin-2, high-dose
corticosteroids (>40 mg prednisone), and the antiepileptics levetiracetam,
topiramate, and phenobarbital.
5.
Benzodiazepines and opioids
relax upper airway musculature and suppress respiratory drive — both worsen OSA
and should be minimized when OSA is a concern.
References
Rado J. Medical Mimics in
Psychiatry: Pitfalls for PCPs. Northwestern Medicine / Northwestern Feinberg
School of Medicine CME presentation, developed in partnership with Pri-Med
Institute.
Benca R. (2023), as cited in
Rado, Medical Mimics in Psychiatry.
Veasey S. (2019); Khazaie H.
(2018), as cited in Rado, Medical Mimics in Psychiatry.
Robertson (2024), as cited in
Rado, Medical Mimics in Psychiatry.
Sahu (2022); Cavalcante-Silva
(2025), as cited in Rado, Medical Mimics in Psychiatry.
Josephson C. (2019), as cited in
Rado, Medical Mimics in Psychiatry.
This post summarizes and
reorganizes third-party CME content for educational purposes; it is not a
substitute for the original presentation or for individualized clinical
judgment.
