To my knowledge, there are a few reasons why this may be. First, serotonin plays a large role in many other psychiatric and medical conditions besides depression. For example, some research shows that the serotonin 1A receptor may be involved in certain symptoms of ADHD (http://www.pni.org/neuropsychiatry/attention_deficit/buspirone/).

For conditions such as OCD and GAD, the answer to your question may be more intuitive: if there is more serotonin in the synapse, and the patient therefore experiences more feelings of wellbeing, it makes sense that compulsions, obsessions, and anxieties may be less pressing or salient to the patient.

The biochemistry of SSRIs is also relevant; they are not as selective to serotonin as one might assume. In addition to acting primarily on 5-HT uptake pumps, less selective SSRIs such as fluoxetine have binding affinities for other receptors and uptake pumps (http://www.preskorn.com/images/columns/9909_fig1.gif). SSRIs' effect on other neurotransmitters may explain why they are effective for the treatment for other disorders. (Source, http://www.preskorn.com/columns/9909.html)

Disclaimer: I'm a senior undergraduate Neuroscience student with a psychoneuropharmacology hobby/research interest, not a medical professional :)

The first thing to remember is that "antidepressants" are an empirical treatment, not a rational treatment. They were not developed to raise serotonin (or norepinephrine) levels based on a neurochemical theory of depression. It's the other way around: once the drugs were known to be effective, their mode of action was investigated, and then the theoretical models were developed. SSRIs are simply a second-generation type of antidepressant. Pharmaceutical researchers decided that since serotonin was the most popular candidate neurotransmitter for the clinical efficacy of the older TCAs and MAOIs, it would make sense to develop drugs that targeted only the serotonin system.

The second thing to remember is that, while there may well be a genuine clinical syndrome we call Major Depressive Disorder, the "symptom" of depressed mood is not specific to that disorder - nor is it entirely isolated from other negative emotional states. In fact, one can argue that depression, anxiety, and panic/fear are best represented as three interlocking rings: each enjoys some degree of specificity, but all three overlap. The personality trait usually called "Neuroticism" captures this nicely. People high in this trait ("N") are prone to developing a variety of more-or-less mild forms of mental disorder, including depression, anxiety disorders, stress-response syndromes, and somatic symptom disorders. So it makes sense that some of the same drugs would "hit" all of these bases.

Wide nets reap greater profits... treatment with drugs that cause dependency are the most profitable of all.... end of story.

Most antidepressants are off patent so no-one is really making any great profit from them any more and haven't been doing so for as lot of years now, which is in itself a reflection of the sorry state of antidepressant research these days - the most likely answer to the question is 'because they are there' - people just trying things because nothing else works - 'serendipity' is still the discoverer of more drug treatments than anything else

Drugs that induce an artificial state of well being or have disinhibitory effects have always been used to 'control' anxiety and depression, the most obvious one being alcohol. How drugs 'work' is often nothing to do with the pharmacodynamics and the fact that they 'work' often gives scant regard for the ADR's that come with the therapeutic effects. Alcohol 'works', morphine 'works' benzo's 'work' and SSRi's work, all of these wonders of human imagination 'work' but at a price.

Analgesics, even those that are non-opioid based have a beneficial effect on mood since chronic pain can cause depression, anxiety and severe mood lability. Take away the pain and the mood gets better, a factor of course in the development of dependency. They 'work' at a price. Plenty of studies have now demonstrated that placebo's 'work', what a shame you can't patent them!

SSRI's have always been used in what used to be called neuroses but the driving force behind the expansion of drug use into areas they were not originally licensed for is to make more money out of them, no different from selling booze really.

Antidepressants can be used in pain conditions. It is also used in patients with Narcolepsy with Cataplexy as antidepressants suppress neurons triggering REM sleep.

I am confused about the last comment.... if antidepressants alter the ability to achieve REM sleep then how can this aspect improve depression?

There should be a much wider dissemination of the serious adverse reactions and interactions caused by some of the drugs known as anti-depressants. Many of these drugs are associated with suicide ideation and their disinhibitory effect is probably responsible for this. Anyone planing on 'extending' the use of anti-depressants or SSRI's needs to be fully informed about their adverse effects and interactions before embarking on off license prescribing. One of the most disturbing ADR's or interactions with many of the SSRI's is their interference with the metabolism of anti-cancer medication such as Tamoxifen. Patients with breast cancer are often understandably depressed and anxious but they should not be prescribed this class of drug. SSRI's inhibit Tamoxifen metabolism and survival rates in breast cancer patients treated for anxiety and depression with these drugs is significantly lower than those who are not prescribed them.

Antidepressants, especially SSRI´s are also used successfully in the treatment of pre-menstrual dysphoric disorder (PMDD). In the DSM-IV, PMDD is classified as a “depressive disorder not otherwise specified”, but in contrast to treatment of depression, SSRI´s are administered only during the luteal phase of the menstrual cycle, and start working within hours or days.

Is that the new name for PMT - pre mensuration tension?

Would it not be more beneficial to balance hormones using bio-identical hormones, use diet, exercise, herbs that have been used by women for centuries, thyroid and adrenal support, meaningful work, hobbies and interests etc? Also address stress from health issues, social, relational, financial and environmental sources etc before giving out a label and a band aid?

I have finally found the source of my 'DSM symptoms not otherwise specified clusters' - Pyroluria and with daily zinc and B6 supplements (along with omega 3 oils, bio-identical progesterone and good multi vitamins) have returned to symptom free health.

Apologies for being so trivial but:

Your autocorrect has hit upon a novel disorder - pre mensuration tension. Good to know the worries I have contemplating data analysis now has a diagnosis!

Dear Heather,

The short answer is no.

PMDD is NOT the novel term, nor the same as premenstrual tension (or premenstrual syndrome, or PMS, as I assume you are referring to).

The symptoms of PMDD are similar to those of PMS, but are more exaggerated and often have more psychological symptoms than physical ones (persistent depression, anxiety, anger and even suicidal thoughts).

Hormone therapy (oral contraceptives, estrogen, GnRH agonists) are considered second-line treatment due to side effects, and there is no compelling evidence for diets, exercise or supplements such as vitamins, calcium or magnesium, in its effect on symptom relief. However, SSRI's have proven very efficient, and there is currently a large clinical trial being conducted by Umecrine Mood in Sweden, seeking to test the effect of a novel candidate drug called UC1010. The first results will be presented Q2 2014.

There are neurobiological explanations (as commented by Monica Lewin, though admittedly not comprehensive) of why "antidepressant" are used for other conditions such as OCD.

Indeed same applies to use of "antipsychotics".

Perhaps its time to avoid using such generalised descriptive terms ("antidepressants" and "antipsychotics") which are clearly not specific.

OCD, Anxiety disorders, PTSD, Bipolar disorders etc

Imram,

Yes, they are prescribed for these disorders, but WHY are they prescribed? What common biochemical pathway is impacted that make SSRIs effective for all these disorders?

Its a cult Neil.... focus on disorder and treatment. You dont get to ask why because no one really knows. I understand Prozac is fluoride based which dulls the senses, lowers IQ and causes people to not care. One of the reasons its added to drinking water, along with a convenient way of disposing of a waste produce which is more toxic than lead. I am amazed how no one asks any questions when someone like me says hey I found causes, addressed them and am now symptom and med free.

Very good question! Very simple response. Depression is by no means a merely psychic disease but rather a ,euro-biochemicla disfunction with multi-systemic features.

I have performed an yet unpublished study showing that bodily signs are a as good signs of depression as psychic ones.

These numerous consequences can, logically, be treated by antidepressants.

Conversely, there presence can ascribe many psychic illnesses to a depressive origin, leading also to an efficient treatment with antidepressant.

You can find the list in my book in french "La dépression et son traitement: aspects méconnus" L'Harmattan Paris 2011 and an abstract on my site bmaroy.free.fr at chapter depressionF&E.

Moreover, neurotransmiters imbalance is an epiphenomenon devoid of any causality, as demonstrated since more than 10 years.

With marketing of pharma-industry and increasing of their profits!

Why not if it cures patients?

I agree with Bernard, but the problem is the drug dependency. The pharmacotherapy shuld be relativ short and in minimal optimal dosis. Always in combination with psychoterapy.

Nikola - re your point about the profit motive, all of the commonly prescribed antidepressants are out of patent so no-one is making any money out of them

This was one of the main reasons why Big Pharma pulled out of psychiatric drug research in about 2010  -

http://www.sciencemag.org/content/329/5991/502.summary

that and their lack of ability to make any progress in developing new drugs because the drug discovery system they were using was terminally flawed

https://www.academia.edu/2240421/The_failure_of_the_antidepressant_drug_discovery_process_is_systemic

Hence until someone decides this is an area worth investing in again we are stuck with 40 year old drugs that don't work any better than placebo

Dear Nikola.

It's very important not to confuse task and means and taboos with evidences.

The only task is to cure, or improve, the patient with minimal negative effects.

I fail to see why dosage should be minimal. In my opinion, it should be optimal.

Short duration of treatment is based on the false concept of short duration of depression itself. Duration should be "enough".

Finally, concomitant use of psychotherapy has a logic for psychic features (probably symptomatic) but not for bodily consequences.

Dear Colin.

We have many medications to try. Of course, having new ones for resistant depression would be useful, but optimal use of the available ones allows a good efficiency, especially when associations are used as needed.

Finally, conspiracy theory is rarely justified.

Dear Bernard, OK. But the first principl in medicine is PRIMUM NON NOCERRE, and the second - THE THERAPY DEPENDENCE OF CAUSE/CAUSES! How many causes have the depressive syndromas?? Many are life event, many organic... How long shuld be the duation of therapy by unhappy mariagge, separation, death....?

Tricyclic antidepressants have been used experimentally in cancer research and have shown multiple effects on reducing cancer cell proliferation in vitro.  This is probably due to protein binding properties.  I am unaware of this being used clinically and the proportionality high doses combined with severe adverse reactions in patients may make reduce the potential for clinical application.  

The first do no harm principle is an important one in this context and the question has to be asked about whether the benefits of taking antidepressants outweigh the harm done by this in terms of side effects and delays in being given more suitable medication

All the recent evidence shows that antidepressants are no more effective than placebo (circa 40% response rate) and that the side effects range from none, to mild to severe with the most dangerous of these being an increase in the risk of suicide at about day 8-9 of chronic treatment  and teratogenesis

Hence, it is doubtful if these drugs would have been given FDA approval if all the evidence available now was available at the time this decision was taken and the increasingly cautious labeling of these drugs seems to reflect this 

Back to the 70th. Mourning is not depression. It was called situational pseudo-nevrosis. In my opinion, it's a complicated but well fitting term. 

Conversely, true depression was called endogenous, whatever it's cause, most frequently genetic.

It's of paramount importance not to confuse causal with modulating factors, frequently masking the less evident genetic factor.

In my opinion, backward movement has been tremendous since this period, principally because of a too durable pull-back on description under DSM rules.

As I stead earlier, efficiency of antidepressant is very dependent of their use and their characteristics fail to fit double-blind, classical methods.

Bernard - most of the evidence showing that current antidepressants are no more effective than placebo (i.e. a response rate of circa 40% only) comes from real world data examining efficacy rates in the clinic. 

See for example

Trivedi MH, Rush AJ, Wisniewski SR, et al. (2006) Evaluation of out-comes with citalopram for depression using measurement-based carein STAR*D: Implications for clinical practice.Am J Psychiatry 163:28-40.

Kirsch, I. Antidepressants and the placebo response. Epidemiol Psichiatr Soc. 2009;18:318–322.

Colman I, Naicker K, Zeng Y, et al. (2011) Predictors of long-term prognosis of depression. CMAJ 183: 1969–1976.

Khan, A., Faucett, J., Lichtenberg, P., Kirsch, I., & Brown, W. A. (2012). A systematic review of comparative efficacy of treatments and controls for depression. PLoS One, 7(7), e41778.

and the STAR-D data itself 

http://www.nimh.nih.gov/funding/clinical-trials-for-researchers/practical/stard/allmedicationlevels.shtml

There is also a tendency for drug effects in older publications to be stronger than in more recently published studies

Papakostas GI and Fava M (2009) Does the probability of receiving pla-cebo influence clinical trial outcome? A meta-regression of double- blind, randomized clinical trials in MDD.Eur Neuropsychopharm 19: 34-40

and whilst we don't fully understand the reasons for this one major influence on the way these drugs are looked at by health professionals is publication bias (where only positive reports make it into print). This has tended to exaggerate their efficacy and is why all more recent meta analyses of clinical trials now also take into account trails lodged with the FDA that were never published.

Pigott HE, Leventhal AM, Alter GS, et al. (2010) Efficacy and effectiveness of antidepressants: Current status of research. Psychother Psychosom 79: 267–279.

There are over 800 medications that list depression as a possible side effect.. As Colin and Nikola are trying to point out depression can be physical, emotional, spiritual, situational, financial, relational even political. A pill can not have positive effect, apart from placebo, on most of these. However a medication that tampers with natural functioning can negatively affect a persons neurological and physical being.

The method of diagnosis can create disheartening stigma, chemical dependence, damaged self worth, relationships and employment prospects.... and when you are feeling bad about all these the answer is more drugs! No wonder suicide is many peoples way out of the nightmare.

Gone are the days a B12 injection was offered, a holiday suggested, diet and addictions questioned and some social support sought. Let alone question society, medicine, the ethics of those who employ you, your mind numbing tv watching, corrupt politics, environmental devastation and admit that perhaps for those who do think for themselves that depression is a possible reaction.

Learning to either numb yourself and/or find joy in the good things around us as well as support our own bodies to be resilient is a personal journey we all have to face at sometime in our lifetimes. Therefore for the most part its social not medical and quick fix solutions can not be the sole focus, especially when they come with high costs. As for a doctor offering antidepressants to someone with back pain the question is what are his/her motives? To meet quotas, be seen covering the possible bases or to really care for their patients well being and recovery?

I am gastroenterologist-internist. Therefore, I have the advantage  to avoid blurring by current psychologic-psychiatric taboos.

It's of paramount importance to criticize everything you have been taught.

Open the eyes and you shall see!

My method works since 35 y. on approximately 90% of my patients. This should interest every doctor concerned  by his patient's cure, even if it violates present taboos.

Heather - all good points except for maybe the back pain example - all the commonly prescribed antidepressants have significant analgesic properties (which some argue is their main and perhaps only useful action) so this isn't as daft as it sounds

e.g.

Dharmshaktu, P., Tayal, V., & Kalra, B. S. (2012). Efficacy of antidepressants as analgesics: a review. The Journal of Clinical Pharmacology, 52(1), 6-17.