Antidepressant

An antidepressant is a psychiatric medication used to alleviate mood disorders, such as major depression and dysthymia and anxiety disorders such as social anxiety disorder. According to Gelder, Mayou &*Geddes (2005) people with a depressive illness will experience a therapeutic effect to their mood; however, this will not be experienced in healthy individuals. Conversely, a systematic review of anti-depressant efficacy, published in 2012, failed to demonstrate superior effectiveness of anti-depressants for treating depression compared to psychotherapy, alternative therapy such as exercise, acupuncture and relaxation, or active intervention controls such as sham acupuncture or therapies not specific to depression. Drugs including the monoamine oxidase inhibitors (MAOIs), tricyclic antidepressants (TCAs), tetracyclic antidepressants (TeCAs), selective serotonin reuptake inhibitors (SSRIs), and serotonin-norepinephrine reuptake inhibitors (SNRIs) are most commonly associated with the term. These medications are among those most commonly prescribed by psychiatrists and other physicians, and their effectiveness and adverse effects are the subject of many studies and competing claims.

Most typical antidepressants have a delayed onset of action (2–6 weeks) and are usually administered for anywhere from months to years. Despite the name, antidepressants are often used to treat other conditions, such as anxiety disorders, obsessive compulsive disorder, eating disorders, chronic pain, and some hormone-mediated disorders such as dysmenorrhea. Some of these uses are FDA-approved and some are off-label. Alone or together with anticonvulsants (e.g., carbamazepine or valproate), these medications can be used to treat attention-deficit hyperactivity disorder (ADHD) and substance abuse by addressing underlying depression. Also, antidepressants have been used sometimes to treat snoring and migraines.

Many drugs produce an antidepressant effect, but restrictions on their use have caused controversy and off-label prescription is a risk, despite claims of superior efficacy. Opioids were used to treat major depression until the late 1950s. Amphetamines were used until the mid-1960s. Prescribing opioids or amphetamines for depression falls into a legal grey area. Research has only rarely been conducted into the therapeutic potential of opioid derivatives for depression in the past sixty years, whereas amphetamines have found a thriving market for conditions as widely arrayed as attention deficit disorder, narcolepsy, and obesity, and continue to be studied for myriad applications. Both opioids and amphetamines induce a therapeutic response very quickly, showing results within twenty-four to forty-eight hours; the therapeutic ratios for both opioids and amphetamines are greater than those of the tricyclic anti-depressants. In a small study published in 1995, the opioid buprenorphine was shown to have potential for treating severe, treatment-resistant depression.

Other medications that are not usually called antidepressants, including antipsychotics in low doses and benzodiazepines, may be used to manage depression, although the use of benzodiazepines can cause a physical dependence. Stopping benzodiazepine treatment abruptly can cause unpleasant withdrawal symptoms. An extract of the herb St John's Wort is commonly used as an antidepressant especially in Europe, although it is labeled as a dietary supplement in some countries. 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 a clinically depressed mood.

Inert placebos can have significant antidepressant effects, and so to establish a substance as an "antidepressant" in a clinical trial it is necessary to show superior efficacy to placebo. A review of both published and unpublished trials submitted to the U.S. Food and Drug Administration (FDA) found that the published trials had a 94% success in treating depression while the unpublished literature had below 50% success. Combined, 51% of all studies showed efficacy. The difference in effect between active placebos and several anti-depressants appeared small and strongly affected by publication bias. There is some evidence to suggest that mirtazapine and venlafaxine may have greater efficacy than other antidepressants in the treatment of severe depression.