選択的セロトニン再取り込み阻害薬（せんたくてきセロトニンさいとりこみそがいやく、Selective Serotonin Reuptake Inhibitors、SSRI）は、抗うつ薬の一種。シナプスにおけるセロトニンの再吸収に作用することでうつ症状、病気としての不安の改善を目指す薬。2009年5月現在、日本国内で100万人以上が使用していると推定されている。
2008年に、認可されている4つの新しい抗うつ薬の、アメリカ食品医薬品局（FDA）に提出された35の臨床試験を結合したメタ分析が広く報道された（SSRIのパロキセチンとフルオキセチン（日本では未認可）、非SSRI抗うつ薬のネファゾドン（英語版）、またSNRIのベンラファキシン（英語版）（日本では開発中止）を含む）。FDAに提出されたが論文としては公開されていないデータを含む出版バイアスの解析を行った。著者のアービング・カーシュは、偽薬に対する抗うつ薬の効果は、統計的に有意だったというものの、「臨床的に有意な」効果のための英国国立医療技術評価機構（NICE）の基準を上回らなかったことを見出した。具体的には、軽症のうつ病に対して効果量（英語: effect size）が非常に小さく、しかし重症度に伴って増加し、非常に重度のうつ病に対しては「臨床的な有意」に達した。重症度と効果の間の関係は、医薬品の効果の増加よりも、重度のうつの患者での偽薬効果による緩和に起因したと考えられる。何人かの研究者は、抗うつ薬の効果量の低い見積りを示唆しているこの研究における、統計上の基盤を疑問視したが、全結果を結合しデータを再分析しても、それでもなおNICEの「臨床的に有意」な閾値を下回ることが見出された（とはいえ、パロキセチンとベンラファキシン（日本では開発中止）はこの閾値を上回った）。
また、近年ではSSRIの長期服用で前頭葉類似症候群(frontal lobe-like syndrome)が起こるという研究がなされている。米国の精神科医、Dr.J.ZajeckaはSSRIを長期に使用した場合、無気力・無関心、疲労感、精神的に鈍い感じが残る状態に陥ることがあるとした。 これらの症状は、SSRIの長期間使用により、前頭葉や脳幹のノルアドレナリンやドーパミン活性が低下し起こると考えられている。これらの症状が出たら処方の変更が推奨される。セルトラリンは、弱いドーパミン再取り込み阻害作用も伴う為、前頭葉類似症候群は起こりにくいとされているが、これも個人差がある。
2001年8月、米国ではカリフォルニアの患者35人が、パロキセチンの重篤な離脱反応で、製造元の英国グラクソ・スミスクライン社を相手に集団訴訟を提訴した。この離脱反応は英国でも問題となり、同社は2003年6月に添付文書での離脱反応が生じるリスク予測を、0.2%から一挙に25%に修正した。 FDAは、2003年6月パロキセチンを18歳以下に使用しないよう勧告、2004年10月には、全抗うつ剤の添付文書に18歳以下での自殺傾向のリスクについて、最も厳しい「黒枠警告」を行うよう指示した。 日本の厚労省は、欧米の動きを受けて、2003年8月パロキセチンを18歳以下の大うつ病性障害には禁忌とするよう添付文書を改訂した。
2009年6月1日に放送された『クローズアップ現代 抗うつ薬の死角～転換迫られるうつ病治療～』で、SSRIの不適切な投与により傷害行為（強盗）に及んだ患者が、医療鑑定で「SSRIの影響がある」と認められた事例が報告された。これは薬害であるが、SSRIの知識に乏しい医師が、SSRI服薬量の急激な増減が危険であることを知らずに、患者の体調報告にあわせて頻繁に投薬量の増減を繰り返していたことも一要因であるとされた。 また、この薬はパニック障害で服用した場合、飲み始めてからきちんとした効果が出るまでに二週間前後の時間を必要とするので注意が必要である。また、服用によって、逆に精神のバランスを崩す可能性もあるので、経過観察には注意を要する。
|Selective serotonin reuptake inhibitor|
|Use||Depression anxiety disorders, and some personality disorders.|
|Biological target||Serotonin transporter|
Selective serotonin re-uptake inhibitors or serotonin-specific reuptake inhibitor (SSRIs) are a class of compounds typically used as antidepressants in the treatment of depression, anxiety disorders, and some personality disorders.
SSRIs are believed to increase the extracellular level of the neurotransmitter serotonin by inhibiting its reuptake into the presynaptic cell, increasing the level of serotonin in the synaptic cleft available to bind to the postsynaptic receptor. They have varying degrees of selectivity for the other monoamine transporters, with pure SSRIs having only weak affinity for the noradrenaline and dopamine transporter.
SSRIs are the first class of psychotropic drugs discovered using the process called rational drug design, a process that starts with a specific biological target and then creates a molecule designed to affect it. They are the most widely prescribed antidepressants in many countries. The efficacy of SSRIs in mild or moderate cases of depression has been disputed.
The main indication for SSRIs is major depressive disorder (also called "major depression", "clinical depression" and often simply "depression"). SSRIs are frequently prescribed for anxiety disorders, such as social anxiety disorder, panic disorders, obsessive–compulsive disorder (OCD), eating disorders, chronic pain and occasionally, for posttraumatic stress disorder (PTSD). They are also frequently used to treat depersonalization disorder, although generally with poor results.
Antidepressants are recommended by the National Institute for Clinical Excellence (NICE) as a first-line treatment of severe depression and for the treatment of mild-to-moderate depression that persists after conservative measures such as cognitive therapy. They recommend against their routine use in those who have chronic health problems and mild depression. There has been controversy regarding the efficacy of antidepressants in treating depression depending on its severity and duration. A comprehensive review conducted by NICE concluded that antidepressants have no advantage over placebo in the treatment of short term mild depression, but that the available evidence supported the use of antidepressants in the treatment of dysthymia and other forms of chronic mild depression. Two meta-analyses of clinical trials published in 2008 and 2011 found that in mild and moderate depression, the effect of SSRIs is small or none compared to placebo, while in very severe depression the effect of SSRIs is between "relatively small " and "substantial". Unlike the NICE study, these studies did not discriminate between the acutely and chronically depressed. The 2008 meta-analysis combined 35 clinical trials submitted to the U.S. Food and Drug Administration (FDA) before licensing of four newer antidepressants (including the SSRIs paroxetine and fluoxetine, the non-SSRI antidepressant nefazodone, and the SNRI (serotonin and norepinephrine reuptake inhibitor) venlafaxine). The authors attributed the relationship between severity and efficacy to a reduction of the placebo effect in severely depressed patients, rather than an increase in the effect of the medication. Some researchers have questioned the statistical basis of this study suggesting that it underestimates the effect size of antidepressants. A 2010 review reached similar conclusions: in mild and moderate depression, specifically that the effect of SSRI is very small or none compared to placebo, while it is clinically significant in very severe depression. However, this analysis included only 6 studies out of the over 2,000 that have been done, involved just 2 medications, and did not involve studies with placebo washout periods typically used as controls.
SSRIs are recommended by NICE over tricyclics due to their superior tolerability. One study showed that SSRIs have greater adverse effects than TCAs in the elderly, though the authors caution that more research is needed. There does not appear to be a substantial difference in efficacy among the various second generation antidepressants (SSRIs and SNRIs).
SSRIs are recommended by the National Institute for Health and Clinical Excellence (NICE) for the treatment of generalized anxiety disorder (GAD) that has failed to respond to conservative measures such as education and self-help activities. GAD is a common disorder of which the central feature is excessive worry about a number of different events. Key symptoms include excessive anxiety about multiple events and issues, and difficulty controlling worrisome thoughts that persists for at least 6 months.
Antidepressants provide a modest-to-moderate reduction in anxiety in GAD, and are superior to placebo in treating GAD. The efficacy of different antidepressants is similar.
SSRIs are recommended for the second line treatment of adult obsessive compulsive disorder patients with mild functional impairment and as first line treatment for those with moderate or severe impairment. In children, SSRIs can be considered as a second line therapy in those with moderate-to-severe impairment, with close monitoring for psychiatric adverse effects. SSRIs are efficacious in the treatment of OCD; patients treated with SSRIs are about twice as likely to respond to treatment as those treated with placebo.
Anti-depressants are recommended as an alternative or additional first step to self-help programs in the treatment of bulimia nervosa. SSRIs (fluoxetine in particular) are preferred over other anti-depressants due to their acceptability, tolerability, and superior reduction of symptoms in short term trials. Long term efficacy remains poorly characterized.
Similar recommendations apply to binge eating disorder. SSRIs provide short term reductions in binge eating behavior, but have not been associated with significant weight loss.
Clinical trials have generated mostly negative results for the use of SSRI's in the treatment of anorexia nervosa. Treatment guidelines from the National Institute of Health and Clinical Excellence recommend against the use of SSRIs in this disorder. Those from the American Psychiatric Association note that SSRIs confer no advantage regarding weight gain, but that they may be used for the treatment of co-existing depressive, anxiety, or obsessive-compulsive disorders.
SSRIs have been used in the treatment of stroke patients, including those with and without symptoms of depression. A recent meta analysis of randomized, controlled clinical trials found a statistically significant effect of SSRIs on dependence, neurological deficit, depression, and anxiety. There was no statistically significant effect on death, motor deficits, or cognition.
A general disadvantage of SSRIs in treating premature ejaculation is that they require continuous daily treatment to delay ejaculation significantly. For the occasional "on-demand" treatment, a few hours before coitus, clomipramine gave better results than paroxetine in one study, while in another study both sertraline and clomipramine were indistinguishable from the pause–squeeze technique and inferior to paroxetine. The most recent research, conducted in 2007, suggests that on-demand treatment with sildenafil (Viagra) offers a dramatic improvement in ejaculation delay and sexual satisfaction as compared with daily paroxetine, with on-demand sertraline, paroxetine or clomipramine, and with the pause–squeeze technique.
General side effects are mostly present during the first one to four weeks while the body adapts to the drug (with the exception of sexual side effects, which tend to occur later in treatment). In fact, it often takes six to eight weeks for the drug to begin reaching its full potential (the slow onset is considered a downside to treatment with SSRIs). Almost all SSRIs are known to cause one or more of these symptoms:
Many side effects disappear after the adaptation phase, when the antidepressant effects begin to come to prominence. However, despite being called general, the side effects and their durations are highly individual and drug-specific. Usually the treatment is begun with a small dose to see how the patient's body reacts to the drug, after that either the dose can be adjusted (e.g. Prozac in the UK is begun at a 20 mg dose, and then adjusted as necessary to 40 mg or 60 mg). Should the drug prove ineffective, or the side effects intolerable to the patient, another common route is to switch treatment to either another SSRI, or an SNRI.
Mania or hypomania is a possible side effect. Users with some type of bipolar disorder are at a much higher risk, however SSRI-induced mania in patients previously diagnosed with unipolar depression can trigger a bipolar episode; however, according to DSM IV-TR, the diagnosis of bipolar disorder requires that the individuals symptoms must not stem from medication side effects, toxins, drug abuse, or another general medical condition.
SSRIs can cause various types of sexual dysfunction such as anorgasmia, erectile dysfunction, diminished libido, genital numbness, and pleasureless orgasm. Initial studies found the indicence of sexual side effects from SSRIs not significantly different from placebo, but since these studies relied on unprompted reporting, the frequency was underestimated. In more recent studies, doctors have specifically asked about sexual difficulties, and found that they are present in most patients.
Symptoms of sexual dysfunction occasionally persist after discontinuing SSRIs. The incidence of this adverse effect is unknown. A limited series of published case reports describe a loss of genital sensation and other side effects continuing years after cessation of therapy.
The mechanism by which SSRIs cause sexual side effects is not well understood. In part, it is thought that stimulation of postsynaptic 5-HT2 and 5-HT3 receptors decreases dopamine and norepinephrine release from the substantia nigra. A number of drugs are not associated with sexual side effects (such as bupropion, mirtazapine, tianeptine, agomelatine and moclobemide, some of which are also not associated with weight gain).
There is no FDA-approved treatment for SSRI-induced sexual dysfunction and there has been a lack of randomized, placebo-controlled, double-blind studies of potential treatments. There is evidence for the following management strategies: for erectile dysfunction, the addition of a PDE5 inhibitor such as sildenafil; for decreased libido, possibly adding or switching to bupropion; and for overall sexual dysfunction, switching to nefazodone.
Cardiovascular side effects are very rare with SSRI use, with a reported incidence of less than 0.0003 percent. SSRIs inhibit cardiac and vascular sodium, calcium and potassium channels and prolong QT intervals. A number of large studies of patients without known pre-existing heart disease have reported no EKG changes related to SSRI use. More recently, however, concerns about cardiac problems have led to a reduction in the recommended maximum dose of two types of SSRI's. The recommended maximum daily dose of citalopram was reduced to 40 mg for most people and 20 mg for those older than age 60 and some others. The recommended maximum daily dose of escitalopram was reduced to 10 mg for those older than age 65; the maximum daily dose for most other people remained unchanged at 20 mg. In overdose, fluoxetine has been reported to cause sinus tachycardia, myocardial infarction, junctional rhythms and trigeminy. Some authors have suggested electrocardiographic monitoring in patients with severe pre-existing cardiovascular disease who are taking SSRI's.
Antidepressants such as SSRIs have some dependence producing effects, most notably a withdrawal syndrome. Their dependence producing properties (depending on the antidepressant) may not be as significant as other psychotropic drugs such as benzodiazepines; however, withdrawal symptoms nonetheless may be quite severe and even debilitating. SSRIs have little abuse potential, but discontinuation can produce disturbing withdrawal symptoms that may be indistinguishable from a reoccurrence of the original illness. Since physical dependence is a reality, discontinuation should be discussed with a medical practitioner before beginning treatment with this class of drugs.
When discontinuing an SSRI or SNRI some doctors may switch the patient to fluoxetine due to its much longer half-life. This may avoid many of the severe withdrawal symptoms associated with SSRI/SNRI discontinuation. This can be done either by administering a single 20 mg dose of fluoxetine or by beginning on a low dosage of fluoxetine and slowly tapering down. Any SSRI or SNRI may be requested in liquid form, which allows very gradual tapering. Alternatively, a patient wishing to stop taking an SSRI/SNRI may visit a compounding pharmacy where his or her prescription may be re-arranged into progressively smaller dosages. For example the lowest dose of cymbalta that can normally be prescribed is 20 mg in gel capsules; a compounding pharmacist may divide this into doses of 20, 15, 10, 5 and 2.5 mg so that a proper tapered reduction may take place.
Several studies have found that SSRI use is related to a higher risk of suicidal behavior in children and adolescents. For instance, a 2004 U.S. Food and Drug Administration (FDA) analysis of clinical trials on children with major depressive disorder found statistically significant increases of the risks of "possible suicidal ideation and suicidal behavior" by about 80%, and of agitation and hostility by about 130%; More infrequently, studies have been inconclusive. However, a recent comparison of aggression and hostility occurring during treatment with fluoxetine to placebo in children and adolescents found that no significant difference between the fluoxetine group and a placebo group. There is also evidence that higher rates of SSRI prescriptions are associated with lower rates of suicide in children, though since the evidence is correlational, the true nature of the relationship is unclear.
In 2004, the Medicines and Healthcare products Regulatory Agency (MHRA) in the United Kingdom judged fluoxetine (Prozac) to be the only antidepressant that offered a favorable risk-benefit ratio in children with depression, though it was also associated with a slight increase in the risk of self-harm and suicidal ideation. Only two SSRIs are licensed for use with children in the UK, sertraline (Zoloft) and fluvoxamine (Luvox), and only for the treatment of obsessive–compulsive disorder. Fluoxetine is not licensed for this use.
It is unclear whether or not SSRIs affect the risk of suicidal behavior for adults.
The FDA findings resulted in a black box warning on SSRI and other antidepressant medications regarding the increased risk of suicidal behavior in patients younger than 24. Similar precautionary notice revisions were implemented by the Japanese Ministry of Health. In 2004 the Medicines and Healthcare products Regulatory Agency in the United Kingdom issued a warning about increases in 'insomnia, agitation, weight loss, headache, tremor, loss of appetite, self-harm and suicidal thoughts' when the medications are used with children and adolescents.
The introduction of a warning regarding the association between SSRIs and suicide by the FDA in 2004 led to a dramatic decrease in prescriptions of these medications to young people. Originally, there were concerns that the decrease in prescriptions caused by the warnings could increase the number of teenage suicides in the US. However, the most recent data from the US National Center for Health Statistics put these concerns to rest. The suicide rates for persons younger than 25 has actually decreased between 2004 and 2007.[original research?] 
Administration during pregnancy of SSRI is associated with an increased rate of miscarriages, birth defects, persistent pulmonary hypertension of the newborn, newborn behavioral syndrome, and possibly long term behavioral problems. The risk of spontaneous abortion is increased about 1.7 fold.
The FDA issued a statement on July 19, 2006 stating nursing mothers on SSRIs must discuss treatment with their physicians. However, the medical literature on the safety of SSRIs has determined that some SSRIs like Sertraline and Paroxetine are considered safe for breastfeeding.
Maternal SSRI use may be associated with autism. A large cohort study published 2013 found no significant association between SSRI use and autism in offspring.
Neonatal abstinence syndrome is a withdrawal syndrome in newborn babies. It has been documented in SSRI treatment. By November 2003, a total of 93 cases of SSRI use associated with either neonatal convulsions or withdrawal syndrome had been reported. Subsequently, the authors of a Lancet study concluded that doctors should avoid or cautiously manage the prescribing of these drugs to pregnant women with psychiatric disorders.
Since the early 80's scientists have used a technique called neonatal clomipramine to produce animals used in depression research. If rats are given the tricyclic antidepressant clomipramine when 8–21 days old, they develop behavioural changes in adulthood that resemble depression in humans. In 1997 Lundbeck found that treatment with the SSRI LU-10-134-C, which only differs from their product citalopram by two atoms could give similar results as clomipramine. Later it was found that neonatal citalopram and escitalopram makes persistent changes in the serotonergic transmission of the brain resulting in behavioral changes, which are reversed by treatment with antidepressants. By treating normal and knockout mice lacking the serotonin transporter with fluoxetine scientists showed that normal emotional reactions in adulthood, like a short latency to escape foot shocks and inclination to explore new environments were dependent on active serotonin transporters during the neonatal period.
But when young mice were treated with the SNRI desimipramine they developed to normal adults, which suggests that serotonin and norepinephrine have different effects in the developing brain. For humans, the developmental stage sensitive to SSRI:s corresponds with the last trimester to the first years of life. A study showed that 4-year old children perinatally exposed to SSRIs behave normally. However, the young mice and rats also seem normal until they reach puberty and develop behavioural disturbances.
The mechanism is currently unknown, but it seems that early life overstimulation of the 5-HT1 receptor that regulates serotonin production results in low serotonin production after puberty.
Persistent pulmonary hypertension (PPHN) is a serious and life-threatening, but rare, lung condition that occurs soon after birth of the newborn. Newborn babies with PPHN have high pressure in their lung blood vessels and are not able to get enough oxygen into their bloodstream. About 1 to 2 babies per 1000 babies born in the U.S. develop PPHN shortly after birth, and often they need intensive medical care. One study has found that PPHN is six times more common in babies whose mothers take an SSRI antidepressant after the 20th week of the pregnancy compared to babies whose mothers do not take an antidepressant.
A population-based cohort study, which included 1.6 million live births in five Nordic countries, of women with filled SSRI prescriptions later than the 20th week gestation by last menstrual period demonstrated an increased risk of persistent pulmonary hypertension (PPHN) compared to control infants (adjusted RR 2.1, 95% CI 1.5-3). The increased risk of PPHN was of similar magnitude for the SSRI class of drugs (Fluoxetine, Citalopram, Paroxetine, Sertraline, Escitalopram). This study showed that the absolute risk of PPHN would only increase the incidence from 0.1 to 0.3 percent of live-births with late prenatal SSRI exposure.
SSRIs appear to increase the risk of bleeding. This includes an increased risk of GI bleeding, post operative bleeding, and intracranial bleeding. SSRIs are known to cause platelet dysfunction.
SSRIs appear safer in overdose when compared with traditional antidepressants, such as the tricyclic antidepressants. This relative safety is supported both by case series and studies of deaths per numbers of prescriptions. However, case reports of SSRI poisoning have indicated that severe toxicity can occur and deaths have been reported following massive single ingestions, although this is exceedingly uncommon when compared to the tricyclic antidepressants.
Because of the wide therapeutic index of the SSRIs, most patients will have mild or no symptoms following moderate overdoses. The most commonly reported severe effect following SSRI overdose is serotonin syndrome; serotonin toxicity is usually associated with very high overdoses or multiple drug ingestion. Other reported significant effects include coma, seizures, and cardiac toxicity.
The SSRIs, in decreasing toxicity in overdose, can be listed as follows:
The following drugs may precipitate serotonin syndrome in people on SSRIs:
Painkillers of the NSAIDs drug family may interfere and reduce efficiency of SSRIs and may compound the increased risk of gastrointestinal bleeds caused by SSRI use. NSAIDs include:
There are a number of potential pharmacokinetic interactions between the various individual SSRIs and other medications. Most of these arise from the fact that every SSRI has the ability to inhibit certain P450 cytochromes.
0 — no inhibition.
- — no data available.
+ — mild inhibition.
++ — moderate inhibition.
+++ — strong inhibition.
Drugs in this class include (trade names in parentheses):
|Selective serotonin reuptake inhibitors (SSRIs)|
SSRIs form a subclass of serotonin uptake inhibitors, which includes other non-selective inhibitors as well. Serotonin-norepinephrine reuptake inhibitors, serotonin-norepinephrine-dopamine reuptake inhibitors and selective serotonin reuptake enhancers are also serotonergic antidepressants.
In the brain, messages are passed between two nerve cells via a chemical synapse, a small gap between the cells. The (presynaptic) cell that sends the information releases neurotransmitters (including serotonin) into that gap. The neurotransmitters are then recognized by receptors on the surface of the recipient (postsynaptic) cell, which upon this stimulation, in turn, relays the signal. About 10% of the neurotransmitters are lost in this process; the other 90% are released from the receptors and taken up again by monoamine transporters into the sending (presynaptic) cell (a process called reuptake).
SSRIs inhibit the reuptake of serotonin. As a result, the serotonin stays in the synaptic gap longer than it normally would, and may repeatedly stimulate the receptors of the recipient cell. In the short run this leads to an increase in signalling across synapses in which serotonin serves as the primary neurotransmitter. On chronic dosing, the increased occupancy of pre-synaptic serotonin receptors signals the pre-synaptic neuron to synthesize and release less serotonin. Serotonin levels within the synapse drop, then rise again, ultimately leading to down-regulation of post-synaptic serotonin receptors. Other, indirect effects may include increased norepinephrine output, increased neuronal cyclic AMP levels, and increased levels of regulatory factors such as BDNF and CREB. Owing to the lack of a widely accepted comprehensive theory of the biology of mood disorders, there is no widely accepted theory of how these changes lead to the mood-elevating and anti-anxiety effects of SSRIs.
Large bodies of research are devoted to using genetic markers to predict whether patients will respond to SSRIs or have side effects that will cause their discontinuation, although these tests are not yet ready for widespread clinical use. Single-nucleotide polymorphisms of the 5-HT(2A) gene correlated with paroxetine discontinuation due to side effects in a group of elderly patients with major depression, but not mirtazapine (a non-SSRI antidepressant) discontinuation.
SSRIs are described as 'selective' because they affect only the reuptake pumps responsible for serotonin, as opposed to earlier antidepressants, which affect other monoamine neurotransmitters as well, and as a result, SSRIs have fewer side effects.
There appears no significant difference in effectiveness between SSRIs and tricyclic antidepressants, which were the most commonly used class of antidepressants before the development of SSRIs. However, SSRIs have the important advantage that their toxic dose is high, and, therefore, they are much more difficult to use as a means to commit suicide. Further, they have fewer and milder side effects. Tricyclic antidepressant also have a higher risk of serious cardiovascular side effects, which SSRIs lack.
David Healy has argued that warning signs were available for many years prior to regulatory authorities moving to put warnings on antidepressant labels that they might cause suicidal thoughts. In late 2004 media attention was given to a proposed link between SSRI use and juvenile suicide. For this reason, the use of SSRIs in pediatric cases of depression is now recognized by the United States FDA as warranting a cautionary statement to the parents of children who may be prescribed SSRIs by a family doctor. The FDA's currently required packaging insert for SSRIs includes a warning (known as a "black box warning") that a pooled analysis of placebo controlled trials of 9 antidepressant drugs (including multiple SSRIs) resulted in a risk of suicidal behavior that was twice that of placebo. At the same time, in adults SSRIs do not increase the risk of suicide.
Critics of SSRIs claim that the widely disseminated television and print advertising of SSRIs promotes an inaccurate message, oversimplifying what these medications actually do and deceiving the public. Specifically, critics allege that manufacturers inaccurately portray antidepressants as 'correcting' chemical imbalances. They contend that without accurately measuring patients' neurotransmitter levels to allow for continuous monitoring during treatment, it is impossible to know if one is correctly targeting a deficient neurotransmitter (i.e. correcting an imbalance), reaching a desirable level, or even introducing too much of a particular neurotransmitter.
Biopsychiatrists believe that, among other factors, the balance of neurotransmitters in the brain is a biological regulator of mental health. In this theory, emotions within a "normal" spectrum reflect a proper balance of neurochemicals, but abnormally extreme emotions, such as clinical depression, reflect an imbalance. Psychiatrists[who?] claim that medications regulate neurotransmitters, and many if not most psychiatrists also claim they treat abnormal personalities by removing a neurochemical excess or replenishing a deficit. On the other hand, Elliot Valenstein, a psychologist and neuroscientist, claims that the broad biochemical assertions and assumptions of mainstream psychiatry are not supported by evidence.
A widely reported meta-analysis combined 35 clinical trials submitted to the U.S. Food and Drug Administration (FDA) before licensing of four newer antidepressants (including the SSRIs paroxetine and fluoxetine, and two non-SSRI antidepressants nefazodone and venlafaxine). The authors found that although the antidepressants were statistically superior to placebo they did not exceed the NICE criteria for a 'clinically significant' effect. For more detail, see the section "Efficacy".
A study in The New England Journal of Medicine on a possible publication bias regarding the efficacy of SSRI medications in the treatment of depression suggests that their effectiveness and risk-benefit ratios may be greatly exaggerated. Of 74 studies registered with the United States FDA, 37 with positive results were published in academic journals, while 22 studies with negative results were not published and 11 with negative results were published in a way that conveyed a positive outcome (one positive study was not published and three negative studies were published with results that were portrayed as negative). Overall, 94% of studies actually published were positive outcomes; when published and unpublished studies were included for analysis, the percentage of positive outcomes was 51%.
Other critics have argued that the existence of an SSRI-related withdrawal syndrome mimicking depression may inflate the therapeutic effect size reported in long-term (more than 6 months) placebo controlled trials of SSRI’s, due to a reliance on randomized discontinuation designs. Discontinuation trials are a variant of the classic 2-arm placebo controlled randomized controlled trials used in shorter placebo controlled studies of SSRI’s.
All SSRIs are approved in the U.S. for use with psychiatric disorders as outlined in the Diagnostic and Statistical Manual of Mental Disorders (DSM IV).
Approved uses for SSRIs vary by country and are determined by the overseeing branch of government in charge of regulating drugs. In the U.S., the Food and Drug Administration (FDA) approves drugs after trial results have been submitted by the pharmaceutical companies. In Europe, drugs can be approved either by the European Medicines Agency for human consumption throughout the European Union or by the regulatory agencies of individual countries for use within those countries.. In Canada, the drug approval process is carried out by Health Canada.
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Hundreds of lawsuits have been filed against drug manufacturers seeking compensation for harm attributed to the use of SSRIs. Suits based on product liability, for example, often allege failure to adequately warn users of potential side effects. Manufacturers have defended many suits on the merits and settled many others. In 2005, the U.S. FDA asked manufacturers to include black box warnings on antidepressant drug packaging. Though a 2007 study purportedly showed that the black box "warnings discouraged use of antidepressants in children and adolescents and... led to increases in suicide rates as a result of untreated depression" an article in the New York Times that ran two weeks later questioned the results of the study, claiming that the data did not support a causal link between the black box warning and increased rates of suicide.
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