1. 3,4-methylenedioxyamphetamine: a synthetic hallucinogen of the phenylisopropylamine family (see phenylethylamine). Because at low doses it acts as a CNS stimulant and euphoriant, MDA was once proposed as an aid to psychotherapy, but this use has not been supported. It is thought that MDA’s psychostimulant properties occur through enhanced neurotransmission of norepinephrine and its hallucinogenic action through augmentation of serotonin transmission. MDA is a metabolite of MDMA and may be responsible for much of MDMA’s action; there is some concern that these drugs and other synthetic amphetamine derivatives cause neuronal degeneration.

2. abbreviation for multiple discriminant analysis.