antidepressants

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Introduction

Antidepressants are medications used in the treatment of depression, but many can also be used in conditions such as anxiety disorders and obsessive compulsive disorder. Most antidepressants are taken orally.

What we already know

To understand antidepressants, it is important to understand the key biological theory of what causes depression. Although not fully clear, depression may be caused by a deficit of monoamine neurotransmitters (e.g serotonin, noradrenaline, dopamine) at certain sites in the brain and so most antidepressants aim to restore this deficit.

Antidepressants can be divided into six groups, based on their mechanism of action:

  1. Selective Serotonin Reuptake Inhibitors (SSRIs)“ e.g. Citalopram, Sertraline
  2. Serotonin-Noradrenaline Reuptake Inhibitors (SNRIs)“ e.g. Venlafaxine, Duloxetine
  3. Noradrenergic and Specific Serotonergic Antidepressants (NaSSAs) e.g. Mirtazapine
  4. Tricyclic Antidepressants (TCAs)“ e.g. Amitriptyline, Imipramine
  5. Monoamine Oxidase Inhibitors (MAO-Is) e.g. Phenelzine, Moclobemide
  6. Miscellaneous“ e.g. Bupropion, Trazodone, Reboxetine

Side effects depend on the mechanism of action and can vary from person to person.

NICE guidelines suggest use of antidepressants in moderate or severe cases of depression only. The risks of antidepressant medication use in mild depression outweigh the risks, so other forms of therapy are recommended in these cases.

Areas of uncertainty

  • The exact mechanisms of action – we are yet to find out exactly why and how many of the antidepressants work (there are inconsistencies in the monoamine theory of depression)
  • How to limit side effects associated with antidepressant use
  • Using antidepressants in special groups -“ limited data exists for which antidepressants (if any) are best to use in pregnant women, children and the elderly

What’s in the pipeline

  • Ketamine has been shown to have promising antidepressant effects, although further randomised placebo-controlled trials are needed (Coyle and Laws, 2015)
  • Research is ongoing into the biological causes of depression and it is hoped that when this is better understood, therapy can be targeted towards the exact cause
  • Further research is also being conducted into the long term effects of antidepressants

References

NICE guidelines CG90 (2009) ‘Depression in adults: The treatment and management of depression in adults’ [PDF]

Semple, D. and Smyth, R. (eds.) (2013) Oxford Handbook of Psychiatry. 3rd ed. Oxford: Oxford University Press. (Publisher)

Coyle, C. M. and Laws, K. R. (2015), ‘The use of ketamine as an antidepressant: a systematic review and meta-analysis.’ Hum. Psychopharmacol Clin Exp, doi: 10.1002/hup.2475 [Abstract]

Acknowledgement

Written by: Josephine Neale
Reviewed by: Helge Hasselmann
Last updated: Sep 2015
Review due: Sep 2016

Our antidepressants Blogs

Can a machine learning approach help us predict what specific treatments work best for individuals with depression?

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Marcus Munafo explores a recent study that uses a machine learning approach across two trials (STARD*D and CO-MED) to try and predict treatment outcomes (primarily focusing on the antidepressant citalopram) for depression.

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CBT plus medication for treatment-resistant depression: the CoBalT RCT long-term follow-up

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Sarah McDonald considers the findings of the CoBalT RCT long-term follow-up, which finds that CBT plus antidepressants are clinically and cost effective for treatment-resistant depression in primary care.

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Work Capability Assessments linked with increase in suicides

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Ian Cummins considers the findings of a recent longitudinal study that measures the impact that welfare reform and disability assessments have had on mental illness and rates of suicide.

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Antidepressants vs placebo for depression: forget the gap

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Ioana Cristea considers the possible causes responsible for the apparent narrowing of the drug-placebo gap, which over the last 30 years has seen estimates of depression symptom reduction from antidepressants fall from 70% to 30%.

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Placebo responding and µ-opioid brain functioning predict efficiency of antidepressants

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Dan-Mikael Ellingsen explores the neurochemistry of placebo effects in major depression, as he reviews a recent study of the association between placebo-activated neural systems and antidepressant responses.

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Antidepressant meta-analyses: big business and bias

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Alex Langford reflects on the findings of a recent study that looks at 185 meta-analyses of antidepressants. It finds that industry involvement in research can lead to biased studies that under-report negative aspects of antidepressants for depression.

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What impact are psychotropic drugs having on our physical health?

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John Baker summarises the findings of a recent review of people with schizophrenia, bipolar disorder and depression. The study looks at the adverse effects on physical health of psychotropic drugs (antipsychotics, antidepressants and mood stabilisers).

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No link between SSRI use and violent crime in over 25s

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Sarah McDonald considers the implications of a recent cohort study of SSRI use and violent crime, which suffered from the usual headline grabbing media coverage, so typical of research about young people, violence, crime, drugs and mental health.

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Depression in patients with alcohol use disorders

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Sally Adams summarises a recent meta-analysis of outcomes for independent and substance-induced disorders in people with depression and alcohol use disorders.

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