An antiepressant is a psychiatric medication or other substance (nutrient or herb) used for alleviating depression or dysthymia ('milder' depression). Drug groups known as MAOIs, tricyclics, and SSRIs are particularly associated with the term. These medications are now amongst the drugs most commonly prescribed by psychiatrists and as well as other physicians, and their effectiveness and adverse effects are the subject of many studies and competing claims. Nutrients for which there are claims of antidepressant activity include phenylalanine, tyrosine, tryptophan, 5-Hydroxytryptophan, and choline.