Medical & substance-induced mimics

Nearly every DSM diagnosis carries the same exclusion: the symptoms are not attributable to a substance or another medical condition. On a case exam, missing a thyroid problem, a withdrawal syndrome or a medication side effect is a diagnostic error — and sometimes a safety one.

The two diagnostic categories.

• Mental disorder due to another medical condition — history, exam or lab evidence shows the symptoms are the direct physiological consequence of a medical illness (for example, depressive disorder due to hypothyroidism), and they are not better explained by another mental disorder or by delirium.
• Substance/medication-induced disorder — symptoms develop during or soon after intoxication, withdrawal or medication exposure, and the substance can produce them. Signs that an independent disorder is present instead: symptoms began before the substance use, or persist for a substantial period (about a month) after acute withdrawal or severe intoxication ends, or there is a history of independent episodes.

Common mimics to know.

• Anxiety/panic — hyperthyroidism, hypoglycemia, cardiac arrhythmia, asthma/COPD, caffeine, stimulants, decongestants, alcohol or benzodiazepine withdrawal.
• Depression — hypothyroidism, vitamin B12 or folate deficiency, anemia, sleep apnea, chronic pain, neurological illness, corticosteroids and some other medications, alcohol, stimulant withdrawal.
• Mania/psychosis — corticosteroids, stimulants, cannabis, hallucinogens, thyroid excess, seizures, brain lesions, autoimmune disease.
• Cognitive or attention problems — head injury, seizures, sleep deprivation, sleep apnea, delirium (acute, fluctuating attention — a medical emergency).
• Somatic or skin-focused symptoms — rule out the underlying medical or dermatologic condition first (for example, before diagnosing excoriation disorder).

Hinge differentials.

• Primary psychiatric disorder — onset unrelated to the substance or illness, and symptoms persist after the medical problem is treated or the substance stopped.
• Delirium — acute onset and fluctuating attention; treat as urgent medical.
• Somatic symptom disorder — real symptoms with excessive thoughts and behaviors about them; medical evaluation may still be needed, but repeated negative workups shift the focus.

On the NCMHCE. The counselor never makes a medical diagnosis — the correct move is referral for medical evaluation (primary care, psychiatry, dermatology, neurology), with a release so you can coordinate. Ask about recent physicals, new medications, supplements, caffeine, alcohol, cannabis and other substance use, head injuries, sleep and menstrual or perimenopausal changes. Watch for red flags that need urgent referral: first onset late in life with no prior history, confusion or fluctuating alertness, focal neurological signs, severe headache, or dangerous withdrawal (alcohol or sedative withdrawal can cause seizures or delirium and needs medical management). Carry a provisional diagnosis while the workup is pending, and revise it when results come back.

Clinical Pearl: Before any diagnosis, ask: could a substance, a medication or a medical condition explain this? If yes or unknown, refer for medical evaluation and keep the diagnosis provisional. Symptoms that start before use or persist about a month after it point to an independent disorder.