An antidepressant 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 medical psychologists, psychiatrists and general practitioners, 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 .
Most antidepressants have a delayed onset of action and are usually taken over the course of weeks, months or years. They are generally considered distinct from stimulants, and drugs used for an immediate euphoric effect only are not generally considered antidepressants. Despite the name, antidepressants are often used in the treatment of other conditions, including anxiety disorders, bipolar disorder, obsessive compulsive disorder, eating disorders and chronic pain. Some have also become known as lifestyle drugs or "mood brighteners". Other medications not known as antidepressants, including antipsychotics in low doses and benzodiazepines, are also widely used to manage depression.
The term antidepressant is sometimes applied to any therapy (e.g. psychotherapy, electro-convulsive therapy, acupuncture) or process (e.g. sleep disruption, increased light levels, regular exercise) found to improve clinically depressed mood. An inert placebo tends to have a significant antidepressant effect, so establishing something as an antidepressant in a clinical trial involves demonstrating a significant additional effect.
