SSRIs are promoted as having fewer unwanted effects than alternatives, to be more acceptable to more patients and to be safer in overdose (and thus to decrease the risk of suicide). Two independent meta-analyses, each starting with a careful search of the literature to identify all properly controlled trials, have reached broadly similar conclusions – that SSRIs do have the edge on alternatives, but not by much.
Results from 62 trials (mostly four to six weeks in duration) showed a 54 per cent dropout rate with tricyclic antidepressants against a 49 per cent dropout with SSRIs. This suggests a decided, not decisive, advantage, as the overall difference is ‘comparatively small and may not be clinically relevant’ (BMJ, 1995; 310: 1433-8). Another analysis of 63 trials, including 16 that compared an SSRI with a non-tricyclic, showed that 3 per cent fewer quit an SSRI because of side effects, with no difference in overall dropout rates or for dropouts due to lack of efficacy (BMJ,1993; 306: 683-7).
Little advantage for SSRIs is suggested by the flow of spontaneous (‘Yellow Card’) reports of suspected adverse reactions to the Committee on Safety of Medicines/ Medicines Control Agency (CSM/MCA). The actual numbers have to be treated with great caution, particularly since relatively few suspected adverse reactions are actually reported – even serious and fatal reactions are usually fewer than one in 10. However, reports for the three main SSRIs, after less than 10 years in use, approximates the total numbers of Yellow Cards reported for all prescribed drugs in one year, and far exceed the numbers for supposedly more troublesome antidepressants (CSM/MCA, 1997). It suggests that sertraline might possibly be a more agreeable starting point than fluvoxamine, but probably otherwise indicate there is little to choose between any of them.
Commonly recognised SSRI side effects (usually affecting at least 5 per cent of patients) include agitation; anxiety; dizziness; headache; insomnia; nausea; nervousness; somnolence; drowsiness and tremor. Other regularly reported effects (1-5 per cent incidence) include loss of libido; sexual dysfunction; impaired concentration; confusion; abnormal dreaming and nightmares; and amnesia. In addition, around 5 per cent of reports relate to aggression, hallucinations, fatigue, malaise and depersonalisation. SSRIs can cause a broad spectrum of psychiatric and neurological side effects, resulting in overstimulation in some cases and sedation in others.