Mood stabilisers: lithium long-term effects: practice question

A Psychiatry question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Psychiatry · Mood stabilisers: lithium long-term effects

Sample item

A patient on lithium for 10 years complains of polyuria and polydipsia, with dilute urine not responding to vasopressin. The likely diagnosis is:

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

B. Nephrogenic diabetes insipidus

Lithium impairs the response of the collecting duct to ADH, causing nephrogenic diabetes insipidus. Other long-term effects are hypothyroidism, hyperparathyroidism, weight gain and rarely chronic kidney disease.

Option by option

  • A. Central diabetes insipidus

    Central DI would respond to vasopressin.

  • B. Nephrogenic diabetes insipidus (correct)

    Correct. Lithium causes ADH resistance in the kidney.

  • C. Primary polydipsia

    Primary polydipsia is not drug induced in this way and urine concentrates when water is restricted.

  • D. SIADH

    SIADH causes water retention and hyponatraemia, not polyuria.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Psychiatry question

What is the answer to this Psychiatry question?

The best answer is B, Nephrogenic diabetes insipidus. Lithium impairs the response of the collecting duct to ADH, causing nephrogenic diabetes insipidus.

Why is "Central diabetes insipidus" not the answer?

Central DI would respond to vasopressin.

Why is "Primary polydipsia" not the answer?

Primary polydipsia is not drug induced in this way and urine concentrates when water is restricted.

Why is "SIADH" not the answer?

SIADH causes water retention and hyponatraemia, not polyuria.

What concept does this question test?

It tests Mood stabilisers: lithium long-term effects in Psychiatry. Other long-term effects are hypothyroidism, hyperparathyroidism, weight gain and rarely chronic kidney disease.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Mood stabilisers: lithium long-term effects?

Learn each diagnosis by its core features and its first-line treatment. Then use the flashcards and the other Psychiatry questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.