In low doses, nutmeg produces no noticeable physiological or neurological response. Large doses of 60 g (~12 teaspoons) or more are dangerous, potentially inducing convulsions, palpitations, nausea, eventual dehydration, and generalized body pain In amounts of 10-40 g (~2-8 teaspoons) it is a mild to medium hallucinogen, producing visual distortions and a distinct euphoria. According to some, the effects have a striking similarity to cannabis intoxication, except with a longer duration, and more side effects. Nutmeg contains myristicin, a weak monoamine oxidase inhibitor.
Comparisons between nutmeg intoxication and MDMA have been made, however this remains speculative. This has recently been disproved by the 2006 paper "Abuse of nutmeg (Myristica fragrans Houtt.): studies on the metabolism and the toxicologic detection of its ingredients elemicin, myristicin, and safrole in rat and human urine using gas chromatography/mass spectrometry" by Hans Maurer et al at University of Saarland. However, use of nutmeg as a recreational drug is unpopular due to its unpleasant taste and its side effects, including dizziness, flushes, dry mouth, accelerated heartbeat, temporary constipation, difficulty in urination, nausea, and panic. A user will not experience a peak until approximately six hours after ingestion, and effects can linger for up to three days afterwards.
A risk in any large-quantity (over 25 g, ~5 teaspoons) ingestion of nutmeg is the onset of 'nutmeg poisoning', an acute psychiatric disorder marked by thought disorder, a sense of impending doom/death, and agitation. Some cases have resulted in hospitalization.