Antidepressants are prescribed mainly for people with depression, although some are also used for anxiety disorders and other conditions, including chronic pain and enuresis. They are one of the most commonly prescribed medications (more than 43 million prescriptions were written for them between April 2010 and March 2011 in England1).

Antidepressants were developed in the 1950s, and their mechanism of action is thought to be by increasing the levels of extracellular synaptic neurotransmitters such as serotonin, noradrenaline, and dopamine; they also have other effects, including increasing hippocampal neurogenesis. The original antidepressants were known as tricyclics because of their chemical structure. Since the 1980s a new generation of antidepressants has been developed and marketed based on their mode of action. The nomenclature for referring to these newer drugs is confusing as they can be classified by several criteria, including the target molecule and the number of neurotransmitter sites involved.2 Box 1 lists antidepressants grouped according to the current nomenclature used by the World Health Organization.

The focus of this article is on selective serotonin reuptake inhibitors (SSRIs) and other newer antidepressants (using the World Health Organization’s nomenclature (box 1)) and their use in adults presenting with depressive disorders. We have excluded non-reversible monoamine oxidase inhibitors such as phenelzine as recent guidelines recommend these should usually be prescribed only by specialist mental health professionals. …